A camera is a device for taking photographs, i.e., creating images of the camera’s surroundings. The name goes back to the camera obscure (pinhole camera), which is the archetype of photography and is presented in more detail below.
Cut through a digital camera.
A camera – whether digital or analog – always has about the same structure. As the central element, it has a lens through which light falls into the camera and creates it. There is a medium behind the lens to detect this image – either an electronic image sensor (digital photography) or a film (analog photography), which stores the image simultaneously. Usually, cameras have a viewfinder to see which part of the scene the camera is shooting. The shutter on the lens is then opened via a button, the trigger, and light falls into the camera for a very short period, often only a few milliseconds, recording the image and storing it permanently.
Digital cameras usually have a monitor that can be used to view recorded images. The monitor is also partly used to control the camera (i.e., to make adjustments) and can also serve as an alternative to the viewfinder. While with analog cameras, the image is recorded on the film, which is also used to save the recording, these functions are separate from the digital camera. The image is recorded with a sensor and stored on an external memory card (rarely in internal memory). Digital cameras also have connections so that the captured photos can be transferred to a television or computer. Alternatively, the memory card can be removed and read out independently of the camera.
The camera obscura (digression)
The camera obscura is the archetype of photography (photography in the sense of the process) that has existed since antiquity. Aristotle (384–322 BC) already describes the essential principle. There is probably also corresponding knowledge in other ancient cultures, which are only poorly documented. For a long time, however, there was only the possibility of the image, not that of automatic storage, so you could at least use it to quickly sketch the motif for a later carefully executed painting. You could get quite accurate perspective representations.
The construction of a camera obscura is very simple so that hobbyists can produce it themselves with little time and material. For a long time, it was no longer of practical importance. Still, it is suitable for a better understanding of photography’s basic principle or experiencing it up close.
Also, increasingly ambitious, adventurous, and creative contemporaries in the age of automatism and computers rely on the trend back to the simple and original, which is why the camera obscura in the form of pinhole cameras has gained in importance again. Precisely because of the automatic exposure systems available today in SLR or system cameras, it has become quite easy even for technical amateurs to use their modern camera as a pinhole camera and thus take correctly exposed pictures.
How a classic camera obscura works.
The camera obscura (“dark chamber”) is in its original form, a completely closed, dark room with a very small hole in the middle of one of the four sidewalls. If you now place an object outside the chamber in front of the opening, you can see an image on the wall in the room, opposite the wall.
If the box has only a simple hole as an opening, the picture will appear blurry. However, if you attach a small converging lens in the hole, you can create sharper images. A camera obscura without a lens, the simplest form, is also called a pinhole camera. The construction with the lens was probably already used in Europe in the late Middle Ages.
The camera obscura doesn’t always have to be a room, a box, or even a cookie jar to achieve the same effect. Of course, you can no longer be in the room yourself to look at the picture, so a common trick is as follows: You cut a relatively large, rectangular hole in a cardboard box in the back wall and stretch a page of parchment paper over it, which you can, for example, attached with tape. Use the needle to pierce a tiny hole on the opposite side. You can then see the image of the object in front of the box on the parchment paper if it is dark enough (for example, a candle or light bulb can be used as an object).
It is easy to think that the hole size is characteristic of the smallest resolvable detail. However, it is also known that diffraction effects play a role in very small holes and deteriorate the resolution again. Given the distance between the hole and the wall (sensor, imaging plane), an optimal hole size can be determined about the resolution, enabling the sharpest images. Also, of course, the hole size, like the aperture in a lens, determines the amount of light that gets into the camera, the smaller the hole, the darker the image. Also, the exact hole shape proves to be critical for the quality of the image. Since the wall in which the hole is has a finite thickness, this can also affect the quality of the image – light is scattered over the length of the hole in a thick wall. For optimal results, very thin sheets are used, into which round holes of a defined size are shot with lasers. As with professional cameras, it is also very important to build your own home. The interior has very dark, well-absorbing walls so that stray light does not reduce the contrast of the captured image.
The original reason why lenses were placed in a larger hole was actually to get a brighter image with the same resolution. However, as so often, you don’t get anything for free. While with the pinhole camera, the sharpness of the image primarily depends on the hole size, but not on the distance from the subject to the camera. With the pinhole camera, everything in the image is equally sharp or out of focus, depending on how you see it. When imaging with a lens, only one area is always sharply represented by an adjustable distance.
Comparison – Photo of a row of houses with a pinhole camera (top) and lens camera (bottom).
You can also attach a light-sensitive film in a camera obscura and then only leave the hole open for a short time. In this way, you will get a permanent image, and in this case, you have done the same thing that analog cameras do.
For single-lens reflex cameras and system cameras with interchangeable optics, pinholes can be obtained relatively cheaply today, which on the one hand, have a hole size optimized for the camera, but on the other hand, also have the appropriate lens connection. With this, and because of the low light output with a good tripod and remote release, everyone can easily experience the simple charm of pinhole cameras without tinkering. This can then be done with the conventional SLR cameras, both with manual exposure as in the old days. Still, mostly these cameras also have an automatic exposure at ‘working aperture’ for non-automatic accessories.
The effect of the pinhole camera can also be observed in the forest, for example. When the sun shines through the trees’ thick branches, which then form tiny holes, you can see small round spots on the ground. These spots, known as “sun thaler,” are images of the sun created in the same way as images in a pinhole camera.
Structure and operation of a digital camera
The basic principle of image formation on converging lenses
The lens is the “eye of the camera” and consists of several lenses through which the light enters and creates an image on the sensor (or film) at the end of the lens. In principle, this group of lenses acts as a converging lens, and, as with every converging lens, the image is upside down. The digital camera then automatically rotates the image by 180 ° so that we can see it again correctly; with the analog film, it doesn’t matter anyway. You will then automatically position the picture in the correct position when viewing it. The optical viewfinders of mirror cameras are pentaprisms that ensure that the image can be viewed the right way round. They also give the SLR cameras their characteristic shape in the upper area.
The camera, and especially the lens, works like the human eye. The human eye, too, has a lens through which the light falls, creating images that are upside down. The human brain then automatically converts them into a correct image. While the eye is imaged on a curved, almost round surface, the sensor or film in the camera is a flat surface, which is why the imaging properties are slightly different. With a camera with a flat sensor, it is not possible to show exactly what can be seen with the eye. With self-made pinhole cameras with analog film material, on the other hand, you can bend the filmstrip at least in one direction, for example, to be able to take better panoramic pictures.
Several lenses are used in the lens for several reasons. By combining different glass materials, it is possible for the light of different wavelengths of the same motif point to be imaged on the same pixel on the sensor. Other aberrations can also be reduced in this way, and the aperture can be accommodated in an optimal position. Through the combination of converging and diverging lenses, the lens’s overall length can also be shortened (telephoto lens) or extended, especially with super wide-angle lenses (retrofocus construction). A shift of lens groups can also serve to change the focal length or to focus.
Light from an infinitely distant object (approximately the sun, for example) falls parallel into the lens and is focused by it at a point, the so-called focus. The distance from the center of the lens to this focal point is called the focal length of the lens. Using the example with the sun, you can guess how the concept of a focal point and focal length is formed. If you position combustible material in the focal point, you can ignite it by the sun’s radiation.
In the meantime, one does not usually want to use a lens to burn the sensor with the help of the sun’s rays, but instead to finally image distant objects with lower light intensity on the sensor. The imaging laws are known from geometrical optics then result in a lens, in which, knowing the focal length of the lens, the image of an object on the sensor surface can be constructed, and the correct distances between the object, lens, and sensor surface can be calculated accordingly. In the case of the usual lenses, which consist of several lenses, the lenses can be moved so that the object can be sharply imaged – if necessary also automatically with the autofocus.
A distinction can be made between outside and inside focus. In the case of external focusing, the distance between the lens group and the sensor is changed like that for the individual lens to achieve a sharp image. Usually, the lens extends forward to focus on close objects. When focusing internally, different lens groups are rather shifted against each other. The length of the lens remains the same, but the focal length changes (somewhat) when focusing on close objects.
The change cannot be seen from the outside of the lens. For example, internal focusing in macro photography of living animals can be quite interesting, so as not to scare them away through the lens moving towards them to focus. Lenses with internal focus are also easier to encapsulate to prevent dust from getting into the lens or the camera. Usually, the lens extends forward to focus on close objects. When focusing internally, different lens groups are shifted against each other, the length of the lens remains the same, but the focal length changes (somewhat) when focusing on close objects. The change cannot be seen from the outside of the lens. For example, internal focusing in macro photography of living animals can be quite interesting, so as not to scare them away through the lens moving towards them to focus. Lenses with internal focus are also easier to encapsulate to prevent dust from getting into the lens or the camera. Usually, the lens extends forward to focus on close objects.
When focusing internally, different lens groups are shifted against each other, the length of the lens remains the same, but the focal length changes (somewhat) when focusing on close objects. The change cannot be seen from the outside of the lens. For example, internal focusing in macro photography of living animals can be quite interesting, so as not to scare them away through the lens moving towards them to focus. Lenses with internal focus are also easier to encapsulate to prevent dust from getting into the lens or the camera. The length of the lens remains the same, but the focal length changes (slightly) when focusing on close objects.
The change cannot be seen from the outside of the lens. For example, internal focusing in macro photography of live animals can be quite interesting, so as not to scare them away through the lens moving towards them to focus. Lenses with internal focus are also easier to encapsulate to prevent dust from getting into the lens or the camera. The length of the lens remains the same, but the focal length changes (slightly) when focusing on close objects.
The change cannot be seen from the outside of the lens. For example, internal focusing in macro photography of live animals can be quite interesting, so as not to scare them away through the lens moving towards them to focus. Lenses with internal focus are also easier to encapsulate to prevent dust from getting into the lens or the camera, which moves towards you to focus. Lenses with internal focus are also easier to encapsulate to prevent dust from getting into the lens or the camera, which moves towards you to focus. Lenses with internal focus are also easier to encapsulate to prevent dust from getting into the lens or the camera.
Since the distance from the lens connection to the plane of the sensor is fixed, the focal length indicates how large the section or angle of view that the camera records.
By moving individual lens groups in the lens, not only can objects be shown sharply, as in the case of inner focusing, by changing the focal length, it is also possible by other shifts for special lenses to change the focal length regardless of the distance from the object to be photographed. These are called varifocal or zoom lenses. By changing the focal length, you can zoom in or out of the scene (dynamic focal length).
However, some lenses have a fixed focal length (fixed focal length) and therefore do not enable zoom. Such fixed focal lengths usually have a higher light intensity or better image quality – it is easy to imagine that it is easier to optimize a lens for a focal length than an entire zoo of moving lenses in a zoom lens.
The lenses are optimized for a certain shooting distance, most for distant objects, although you can also focus on closer objects. Macro lenses are more optimized for taking close-up objects, but they usually have excellent imaging properties for distant objects. With macro lenses, special emphasis is placed on the image field’s low distortions, generally on high imaging performance.
Image stabilization systems can also be installed in some lenses. These try to compensate for the shaking of the photographer. As an alternative to this more complex optical variant, image stabilization systems are also built into the camera that shifts the sensor. These are usually designed a bit simpler than the optical ones in the lens, i.e., not optimized for the respective lens and correspondingly less effective but can be used equally for all lenses.
Some digital cameras have a digital zoom. However, only the central part of the image sensor is enlarged, accompanied by considerable quality losses. This enlargement can also be carried out later – and usually with a better result – so digital zooms are best left off.
Camera lens with maximum open aperture
The aperture is the lens’s opening and can often be regulated, i.e., it can be opened further. More light falls into the camera in a one-time unit, or it can be closed further, then less light falls into the camera within a one-time unit. The aperture is a mechanical component that consists of individual overlapping lamellae that slide over each other to reduce the opening. It affects the exposure and depth of field.
A small aperture corresponds to a large aperture (i.e., a lot of light) and vice versa. With a large opening, you also have a shallow depth of field and turned around. With very small apertures, the effect of diffraction occurs, making the wave properties of the light noticeable. Diffraction makes the image more blurred overall. An imaginary point of the object is expanded to a flat disk on the sensor by diffraction at the aperture.
If the disk becomes significantly larger than the distance between two neighboring pixels of the sensor, the diffraction effect becomes visible. The effect is particularly noticeable when combining low-light lenses with sensors with very small pixels – which is often found with cheaper camera models or cameras built into mobile phones.
The aperture is similar in structure to the central shutter (see next section), but is located elsewhere in the lens, so it has a different function in the beam path. In analogy to the human eye, it corresponds to the pupil. The pupil of the eye regulates the amount of light that falls into the eye – it widens in the dark so that more light enters, and narrows in the light.
Properties of a lens
Lenses can be examined and compared according to different properties. These include:
- The lens focal length, for example, 8 – 32 mm.
- The format factor or an equivalent of the focal length in 35 mm format (35 mm format), for example, 28 – 112 mm (format factor 3.5 about the above lens focal length).
- The light intensity (“initial aperture”), for example 1 / 2.8 – 1 / 4.0.
- The lens diameter or the filter thread, for example, 52 mm (this information is important if you want to buy accessories such as filters or lens hoods).
- The available apertures, for example, 2.8, 4, 5.6.
- The quality of the anti-reflective coating and the suppression of stray light
- Compensation or reduction of aberrations
- Resolution at the respective aperture depending on the position of the image on the sensor
- For autofocus lenses, type of drive motor
- Possibility and efficiency of manual focusing, and overriding the autofocus, existence of distance information.
- For zoom lenses, how to set and display the focal length
- With built-in image stabilizer: type, available working modes, efficiency
- Filter thread diameter, type of sun visor lock
This information will usually be found in the camera or lens datasheet, although the available apertures are often not explicitly stated. The individual terms, such as focal length and light intensity, will be explained in more detail later.
In or behind the lens, which is closing. A film (and also the sensor in digital cameras) is extremely sensitive to light and may only be exposed for a very short time in normal daylight. Otherwise, you get a white (completely overexposed) image. The shutter of a classic camera is always closed, and only when the photo is taken does it open for a very short time (for example, 1/500 s, i.e., 0.002 s). There are three basic types of closures.
Central locking ]
An arrangement of curved slats is used for the central shutter, which opens for a short time and enables exposure. Most cameras with a built-in lens use this technology, whereby extremely short exposure times (for example, 1/1000 second or less) are relatively difficult to implement. In the case of analog cameras, this technology was initially used in the initial phase but was later increasingly replaced by the slit shutter described in the following section. Since digital compact cameras often have very small sensors and lenses, the central shutter is now used more frequently, since, with small lens diameters, it is easier to achieve short exposure times with central shutters.
The central shutter is also popular with large-format cameras because it can be easily realized even for large diameters of the lens and image area. The central shutter is either located at a suitable point in the lens or in the camera in front of the image area. Housing in the lens has several disadvantages: Each lens must contain this quite complex component. An auxiliary lock is required to change the lens to prevent light from falling on film or image sensor when changing the lens. However, one advantage of this type of shutter is that the entire image area is always exposed at the same time.
The second type is the slit closure. Here the closure consists of two metal plates, which are also called curtains. The first curtain is closed, and the second is opened. When the exposure is started, the first curtain also opens. The light now falls through the lens. When the exposure time has expired, the second curtain closes and blocks the incidence of light again. The curtains then return to their starting position. With very short exposure times, the second curtain closes while the first is still opening (the second curtain “follows”). This is the only way to achieve extremely short exposure times, such as 1/4000 second.
This creates a “slit” who wanders from top to bottom (or from right to left) and gradually exposes the image for a minimal moment. The following applies: the shorter the exposure time, the narrower the slit. In contrast to the central shutter, short exposure times mean that the entire sensor is not exposed at once, but only part of it. In the case of a slit shutter, this can lead to image distortion in the case of fast-moving subjects or a fast-moving camera and a short exposure time because, due to the small, open slit, the subject is captured in a slightly different movement phase at every point in time of exposure.
The distortion can be seen, for example, when picking up helicopter rotors or racing cars at high speed. The shorter the exposure time, the narrower the slit. Unlike the central shutter, short exposure times mean that the entire sensor is not exposed at once, but only part of it. In the case of a slit shutter, this can lead to image distortion in the case of fast-moving subjects or a fast-moving camera and a short exposure time because, due to the small, open slit, the subject is captured in a slightly different movement phase at every point in time of exposure. The distortion can be clearly seen, for example, when picking up helicopter rotors or racing cars at high speed. The shorter the exposure time, the narrower the slit.
Unlike the central shutter, short exposure times mean that the entire sensor is not exposed at once, but only part of it. In the case of a slit shutter, this can lead to image distortion in the case of fast-moving subjects or a fast-moving camera and a short exposure time because, due to the small, open slit, the subject is captured in a slightly different movement phase at every point in time of exposure. The distortion can be seen, for example, when picking up helicopter rotors or racing cars at high speed. In the case of a slit shutter, this can lead to image distortion in the case of fast-moving subjects or a fast-moving camera and a short exposure time because, due to the small, open slit, the subject is captured in a slightly different movement phase at every point in time of exposure.
The distortion can be seen, for example, when picking up helicopter rotors or racing cars at high speed. In the case of a slit shutter, this can lead to image distortion in the case of fast-moving subjects or a fast-moving camera and a short exposure time because, due to the small, open slit, the subject is captured in a slightly different movement phase at every point in time of exposure. The distortion can be seen, for example, when picking up helicopter rotors or racing cars at high speed.
Because the shutter must be fully open for flash photography, the shortest exposure time the shutter is still fully open is the so-called flash synchronization time. In modern cameras, depending on the shutter and sensor size, this is 1/125 second to 1/300 second. To record fast subjects with flashlights, the flash is used as the only light source if possible and is chosen to be short in time, while the flash sync time is set in the camera.
In the so-called short-term synchronization, on the other hand, the flash duration is selected to be longer than the flash synchronization time, and the flash output is as constant as possible over this period, while a short time is preselected via the slot shutter. This is not used for fast motifs but above all,
Because central shutters always completely expose the sensor, the problem of flash synchro time does not arise.
The third type of ‘shutter’ is only possible with digital cameras, sometimes combined with a conventional shutter. For cameras with ‘live view,’ where you do not look through an optical viewfinder, but only on a monitor, the classic, mechanical shutter can also be completely saved. The exposure time is realized purely via the sensor. Electronics ensure that it is only light-sensitive for the exposure time, or it is read out before and after the exposure time. At the same time, the ‘live view’ corresponds to a constantly repeated reading. That is why one speaks here of an electronic lock. This enables very short exposure times, such as 1/16000 seconds, to be achieved.
When controlling and reading out the image sensor, there are technical problems that prevent the image sensor from being exposed everywhere at the same time as with the central shutter, which is why this method of setting the exposure time can lead to similar artifacts as with the slit shutter. In this respect, this method does not avoid the distortions known from the slot closure but replaces them with similar ones.
Although this technology seems to be very promising and significantly cheaper than mechanical shutters, this technology does not seem to have prevailed. Most of the time, modern SLR cameras are only produced with a slit shutter, because in practice the electronic shutter tends to have other specific artifacts and higher image noise, which can be found in the ‘Live-View,’ i.e., with an open shutter even with current models or inexpensive cameras without a mechanical shutter. For higher-quality cameras, however, the ‘Live-View’ is ended for recordings. The shutter is closed, and the sensor is started up ‘normally,’ with the slit shutter again determining the exposure time. Nevertheless, the previous ‘live view’ has caused the image sensor to heat up and thus increased image noise. For critical recordings, a camera with an optical viewfinder should, therefore, be preferred, and an optional live view, if available, should be avoided.
The image sensor
The image sensor is a small chip that registers the incident light in digital cameras and converts it into an image. It is located where the film sits on the analog cameras. While a new piece of film is used for every image in the film material, the same image sensor is always used for all images from a digital camera. This has several consequences:
- No film has to be transported.
- The contamination of the sensor remains until the next cleaning.
- Defects are not easy to fix with a new film, so the sensor is not easy to replace. For this, the entire camera is usually replaced.
The image sensors of the compact cameras and bridge cameras are very small; the camera remains manageable due to the small focal lengths of the lenses and nevertheless enables a relatively large amount of zoom. However, the small size always implies a low sensitivity to light or a low resolution.
The smaller the image sensor is, the closer the individual pixels are to each other with the same pixels. The individual pixels are then necessarily smaller and generate fewer charge carriers, which requires a higher amplification of the signal. Therefore, and since camera sensors also heat up during recording, the image noise increases with increasingly small sensors – even if modern cameras can retouch this to a certain extent today. As already explained, the combination of low-light lenses or heavily drawn apertures together with small pixels can quickly reveal diffraction effects, which means that the images become blurred, which is why compact cameras often do not even allow them to be strongly dimmed down, or always in automatic mode if possible open aperture,
The size ratio between some known sensor types
For historical reasons, the size of image sensors is usually given in inches and shown as fractions. The value indicates the outside diameter of a fictitious image recording tube with the same sensor size; the length of the sensor’s diagonal is almost two-thirds of this value (a “one-inch picture tube” had a diagonal of the photosensitive surface of about 16 mm). The specification 1 / 2.7 “means that the diagonal of the sensor is two-thirds of 1 / 2.7 inches or 0.235 inches. One inch is 2.54 cm, so the camera sensor has a diagonal of 0, 59 cm. Most camera sensors of compact cameras will be in the range of 0.5 to 1 cm diagonal.
Since a sensor has both height and width and the ratio of height to width can differ for different sensors, the diagonal is not sufficient to characterize the sensor, nor is the total number of all pixels. With the same diagonal, a square sensor has more area than a non-square one. The more the height and width differ, the smaller the sensor’s area with the same diagonal.
Although the sensor size can vary from camera to camera, there are some quite common formats:
- 1 / 3.2 “(0.50 cm), 15.3 mm²
- 1 / 2.7 “(0.59 cm), 21.6 mm²
- 1 / 2.5 “(0.64 cm), 24.96 mm²
- 1 / 2.3 “(0.70 cm), 29.5 mm²
- 1 / 1.8 “(0.89 cm), 38.88 mm²
- 1 / 1.5 “or 2/3 (1.1 cm), 58.08 mm²
- Four thirds (2.2 cm), 17.3mm x 13.0mm = 224.90mm²
- Foveon (2.5 cm), 20.7 mm x 13.8 mm = 285.66 mm²
- APS-C (2.75 cm), 22.2 mm x 14.8 mm = 328.56 mm²
Due to the representation as a fraction, you have to consider that the smaller the denominator (e.g., 2.3 instead of 2.5), the larger the camera sensor.
For example, sensors used for larger cameras have the following dimensions:
- 35mm format (“full format”, 4.32 cm), 36 mm x 24 mm = 864 mm²
- Medium format (6 cm), 48 mm x 36 mm = 1728 mm²
Slight deviations are possible.
While the difference between the medium and small format only corresponds to a halving of the area, i.e., costs about one exposure level, the area of the small formats, on the other hand, decreases dramatically.
The image sensor on a circuit board
The image sensor consists of a rectangular array of individual, microscopic light sensors. For most cameras, a light sensor corresponds to a pixel (pixel) of the photo. However, since not every pixel is sensitive to every color in this camera, most pixel information is always calculated by interpolation via the neighboring pixels. A camera sensor with 4000 horizontal and 3000 vertical pixels can, therefore, take photos up to 4000×3000 pixels (i.e., 12 MP).
However, the number of pixels only states the maximum number of pixels that can be used. The number of pixels used can often be reduced by selecting a format or averaging over neighboring pixels to save images with a smaller number of pixels. For example, if the camera offers 3000×2000 pixels, the manufacturer will give it 6.0 megapixels. A photo that is taken in 4: 3 format (3000×2000 is 3: 2 format) would be taken with a maximum of 2666×2000 pixels, so the 3000 pixels in the horizontal cannot be fully used – that is only around 5, 2 MP. Therefore, the recording format or the format of the sensor plays a certain role in whether the full number of megapixels in a certain format can be used at all. In some cases, however, the sensors are also dimensioned to reach approximately the specified number of pixels in all formats. Depending on the format selection, different pixels are then omitted on the outside, i.e., either those in width or height, so that all pixels of the camera is never used. Also, when it comes to the achievable resolution, there is the resolution limit of the optics, which practically always limits the achievable resolution with small sensors. As already indicated, diffraction effects can also limit the resolution. Also, when it comes to the achievable resolution, there is the resolution limit of the optics, which practically always limits the achievable resolution with small sensors. As already indicated, diffraction effects can also limit the resolution. Also, when it comes to the achievable resolution, there is the resolution limit of the optics, which practically always limits the achievable resolution with small sensors. As already indicated, diffraction effects can also limit the resolution.
Of course, you can also generally choose smaller photo formats. A sensor with 4000×3000 pixels can also take a picture in the format 1600×1200. In the case of digital zoom, not all pixels are used, or the photo is first taken with all pixels, for example with 4000×3000, and then calculated by the camera to 1600×1200.
Types of image sensors ]
There are three main types of image sensors:
- CCD sensors
- CMOS sensors
- X3 sensors
CCD sensors are the most commonly used sensors in compact cameras. The individual pixels are read out line by line, comparable to a scanner that scans an image step by step. At the beginning of digital photography, they provided better quality than the CMOS sensors; however, the CMOS sensors have been developed in such a way that they are no longer inferior to the CCD sensors.
With the CMOS sensors, the individual pixels are relatively independent; they are not read out line by line, but each pixel can be accessed directly. Its brightness value can be determined. This means that the captured images can be processed faster than with the CCD sensor; however, since each picture element has its capacitor to provide direct access to the information, more electronics are accommodated on the sensor than with the CCD sensors. If the arrangement is awkward (especially in older models), there are also conductor tracks and other components in addition to the light-sensitive pixels. In newer models, however, the wiring is usually done from the rear, and microlenses ensure almost complete coverage of light.
CMOS sensors are cheaper to manufacture, do not heat up as much as the CCD sensors, and are less prone to failure. A disadvantage with unskillful interconnection is a lower contrast range, in some cases less sensitivity to light and greater susceptibility to noise – however, modern digital cameras with CMOS technology practically no longer have such disadvantages compared to CCDs.
The pixels of the CCD sensors and CMOS sensors can initially only perceive brightness gradations, i.e., differentiate between black and white and individual gray levels. A so-called mosaic filter is placed on the sensor in most sensors so that a color image can be created. It consists of a grid of red, green, and blue dots. Each point only allows its color to pass through – red points, for example, only allow red light to pass through. Each pixel color can then be interpolated from the amount of red, blue, and green light from neighboring pixels. The better and more precise this calculation (“interpolation”) is done, the better the colors can be displayed at the end. However, such interpolations can also cause incorrect representations, especially for structures with strong contrast that are only one pixel wide in the image or if they are regular but are not exactly aligned with the sensor’s pixel pattern. To increase the light output, each pixel is also equipped with a microlens, which then focuses the light on the light-sensitive area.
In addition to the mosaic filters of the red/green/blue type in a checkerboard arrangement, there are rarely anywhere a pixel of a group of four works without a color filter, i.e., only absorbs the intensity with high sensitivity. Because the microlenses in the corners of a square pixel are not functioning optimally, an arrangement in the form of a honeycomb would be more effective in terms of sensitivity and resolution and the reduction of incorrect representations of small details. However, the method is more complicated to produce. It is more difficult to calculate a normal pixel image from such a pattern because the pixels are arranged with a different symmetry. However, it is also possible to place a colorless sensor on the corner of the colored sensors to exploit their high sensitivity there,
There are numerous options for optimizing the sensitivity and resolution of sensors, which has not yet been completed. In any case, the filtering means that most of the incident light is not used because it has the wrong color for the respective pixel. Since the pixel sizes are still large compared to the wavelength of the visible light, no quantum effects can be used that would allow one to simply detect the light of the wrong wavelength on the neighboring pixel with the right filter.
Thus, the principle of color formation works according to the RGB model (RGB color mixing) presented in the previous part.
The X3 sensor works a little differently in terms of color representation. It is also a CMOS sensor but does not use a grid to generate the colors. On the other hand, use is made of the fact that the light’s penetration depth depends on the sensor material’s wavelength. The depth of the sensor is divided into three zones, which are then read out individually. The ratio of the individual zones’ intensity can then be used to calculate which wavelength the incident light was likely to have. The layer principle is similar to the analog color film, but the color sensitivity per layer is better separated.
This type of sensor at least does not interpolate over neighboring pixels to determine colors, so it has better resolution and higher sensitivity with the same pixel size and a low tendency to produce artifacts in motifs with regular fine structures. However, because the least light reaches the deepest layer, the noise depends on the color channel. When reconstructing the color, this sensor type also appears to have greater problems than the one with the color pixels next to one another. Also, there are no sensors in a small or medium format. One camera manufacturer only uses the sensor type, so it cannot be combined with lenses from other manufacturers.
A viewfinder is an important tool for the photographer; it shows which area of the scene the camera records. There are two types of viewfinders in digital cameras today: an optical viewfinder and a digital viewfinder. With analog cameras, there is usually only one optical viewfinder.
The optical viewfinder
The optical viewfinder is the classic viewfinder. In compact cameras consists of a small window with lenses through which the photographer looks and thus sees the detail that the camera records with the currently set focal length. Of course, the viewfinder can only show the exact section if it is located where the film or image sensor is located (i.e., on the lens). Since it cannot be there structurally, it is usually attached above the lens, often to its left.
Since the viewfinder of compact cameras is slightly offset from the lens, it can be seen that the viewer cannot exactly see what is being recorded at the end; it shows a slightly offset image. The degree of displacement relative to the image size is particularly large for close-up subjects. Still, it decreases with increasing distance until it hardly plays a role in the distance. So the problem is that the image that the camera shows has a slightly different section at the end than was originally seen in the viewfinder. This problem is also called parallax error; in the worst case, the photo at the end lacks details that you originally wanted to show. Of course, the reverse can also happen, so that things appear on the picture that you did not want to show (for example, a protruding house wall, etc.). Another problem occurs with zoom lenses. It is quite complex to adapt the focal length of the viewfinder image to that of the taking lens.
Schematic representation of the parallax error
However, the parallax error is rather small if the subject is not very close. Many amateur photographers may not even notice him. Still, you should know that the optical viewfinder of a compact camera does not show exactly what the camera is going to take for detailed or demanding shots.
Another disadvantage of the optical viewfinder of compact cameras is that it only shows which section is being photographed. It does not show what the photo will look like at the end, which means that it does not take into account the aperture values and shutter speeds set, possible noise due to too high ISO values, etc. It also makes no statement about the focus.
How a reflex camera works
SLR cameras offer a solution to the parallax error. Here, the viewfinder is also located above or next to the lens. Still, there is sophisticated technology in the viewfinder window itself: an arrangement of lenses and prisms ensures that when looking through the viewfinder window, the light is directed through these optical components to the lens and thus one looking through the lens of the camera. This shows exactly what the camera will record later. If the picture is then taken, the last mirror in the lens flips up, and the shutter opens. This means that the light no longer falls on the viewfinder, but on the film or sensor. A small disadvantage is that the viewfinder is not available while the picture is being taken (generally not a problem). The image noise of the sensor or incorrect exposures is also not visible in the viewfinder. However, you can use the sensitivity of your eye to recognize motifs when the subject is dark. In problematic situations, the eye can often judge the focus better than the autofocus, which usually relies on more light than the sensor, which will later be used for recording. This is usually favored by the fact that the aperture is focused on the aperture open, meaning that the field’s depth is very small compared to the working aperture. However, you can use the sensitivity of your eye to recognize motifs when the subject is dark at night. In problematic situations, the eye can often judge the focus better than the autofocus, which usually relies on more light than the sensor, which will later be used for recording. This is usually further favored because the aperture is focused on the aperture open, meaning that the depth of field is very small compared to the working aperture. However, you can use the sensitivity of your eye to recognize motifs when the subject is dark at night. In problematic situations, the eye can often judge the focus better than the autofocus, which usually relies on more light than the sensor, which will later be used for recording. This is usually further favored because the aperture is focused on the aperture open, meaning that the depth of field is very small compared to the working aperture.
Another solution is the electronic viewfinder.
The electronic viewfinder
Many digital cameras, including cameras in the higher price range, often only offer an electronic viewfinder, also known as a ‘live view.’ That is, the monitor serves as a viewfinder, showing what the camera will take. The clear advantage here is that not only is the exact section shown (as with the optical viewfinder), but the camera also automatically shows how the photo will be taken. So you can see before the picture is taken that the photo is too dark or light (wrong exposure), looks blurred (wrongly focused), the picture is noisy (ISO value too high), etc. You can also experiment with it ideally without every time a parameter (exposure value, aperture value, ISO value, color filter, white balance, etc.) is changed. A new picture has to be taken.
However, the noise in the ‘Live View’ can be different than in the actual recording. Since ‘live view’ often takes place at the working aperture, the depth of field can be judged passively. Still, precise focusing is often more difficult, also because the camera’s monitor has far fewer pixels than the sensor. For manual focusing, you can often enlarge the central section of the image to get a resolution similar to that of an optical viewfinder. A problem with electronic viewfinders is also the use of the working aperture for manual flash photography. There is simply no longer any motive in the viewfinder, the viewfinder fails. In contrast, the same situation with an optical viewfinder is usually completely unproblematic as long as there is still some additional light.
The monitor also provides waste heat, which heats the camera and thus the sensor, which can increase the noise when recording.
There is no parallax error in the electronic viewfinder like in the SLR camera; the camera shows what it will take.
It may almost seem that the electronic viewfinder offers many advantages and that you don’t need the optical viewfinder anyway. It must at least be mentioned here that the monitor’s size is decisive for how well you can judge the scene in the end. Since cameras are often supposed to be small and handy, the monitor inevitably turns out to be small, and the assessment of the scene to be recorded can be difficult. Also, the effects of light, such as sunlight, often disturb the small monitors, even if the color quality and brightness adjustment have improved significantly since the beginning. Ultimately, you don’t see on the monitor which image is being taken. Still, rather you see a representation of the current image in the sensor, which works a little differently when recording than in continuous operation of the ‘Live View.’
Many photographers also have fundamental problems with the changeover; While they kept the camera close to the eye and then pulled the trigger at the right moment, they now have to hold it well in front of their body. It takes time to get used to the new posture; nevertheless, the closer you hold the camera to your body, the safest you can hold it – so this is a clear additional advantage with an optical viewfinder. If you hold the camera further away from your body to be able to view the monitor, you can easily shake the picture or have to choose significantly shorter exposure times or rather a tripod to be able to take a good picture.
Also, the monitor consumes energy that is generated as waste heat in the camera and reduces the number of shots with the same battery. At the same time, the optical viewfinder requires practically no energy from the battery. Even historic cameras were already connected in such a way that displays in the viewfinder only consumed electricity when the camera trigger was tapped. The electronic search always needs an energy supply if you want to see anything at all. With a manual setting of aperture and shutter speed, there may be further problems with a usable display in the electronic viewfinder.
However, the electronic viewfinder is often sufficient for everyday use and is characterized by the advantages already mentioned. If the camera is also mounted on a tripod, the display on the monitor facilitates contactless operation to avoid camera shake. Therefore, it is practical if the camera has both an optical viewfinder and an electronic viewfinder so that the photographer has the choice of which is more suitable depending on the situation.
Pressing the shutter button starts the process of capturing images. It usually takes only a fraction of a second, but with a long exposure, it can take several seconds and, in extreme cases, even minutes or hours. Most digital cameras today offer the function of continuous shooting ( continuous shooting). The camera records images as long as the shutter button is pressed. This means that individual pictures can be taken in quick succession than in simple mode. Some cameras offer the option to refocus between shots.
Cameras also offer a self-timer (English: timer, self-timer). If this is activated, the cameras take a few seconds, depending on the setting, to take the picture. Typical times are 2 seconds and 10 seconds; some cameras also allow the individual setting of a value. This enables group shots, for example, in which the photographer himself appears in the picture. Self-timers are also used at slow shutter speeds to avoid blurring from camera shake.
A little time elapses between triggering an actual image capture, which is known as the trigger delay. The camera first takes time to set the exposure and focus and some time to start the exposure process. If the focus and exposure have already been calculated (half-pressed shutter release or preselection), the delay is significantly less. However, a few milliseconds will still elapse before the picture is taken. This should be taken into account when taking pictures with fast-moving objects or people.
The release delay was often considered at the beginning of digital photography; for some models, it was several seconds. On the other hand, today’s cameras have a relatively short delay, which should no longer prove to be annoying in everyday recordings.
It should also be noted that autofocus can lead to considerable delays, especially in critical lighting conditions. If you know where the subject is or will be, it can be worth deactivating the autofocus to save time when it is triggered.
There may also be small delays when shooting with flash units, for example, if the flash mode requires that a pre-flash is triggered and evaluated. If you already know what you need here before recording, you can also reduce delays with another mode or a manual pre-selection.
It may also be important to be able to connect a remote release. If the connection is suitable, you can decide whether this should be a cable connection or whether infrared or radio releases are more suitable. Such a connection can also be used to connect ‘timers’ devices that automatically trigger the camera at fixed time intervals or even select or vary other properties.
Most of today’s compact cameras use SD cards to store photos.
Digital cameras usually store the photos on commercially available memory cards, with the SD card being widely used. It is relatively small and offers a high storage capacity – 4, 8, and 16 GB are standard capacities today, which can also store photos in large numbers in large numbers. Please note that there is a format limit of 2 GB, older cameras cannot manage larger file systems, so before buying a new card, you should always pay close attention to whether the camera can use more than 2 GB cards.
For large cameras, CF cards are common, which allow higher processing speeds, but are also less compact.
Some very compact devices, such as cell phones, can also use micro SD cards with similar properties to SD cards in terms of storage but are significantly smaller. While CF cards are still quite handy and SD cards are still roughly thumb-sized, handling the micro SD cards is already noticeably more problematic due to the edge length of approximately 1 cm and a thickness of approximately 1 mm. For other reading, there are usually adapters into which the micro SD card can be inserted, after which the adapter can be used as an SD card.
Some cameras also have an internal memory, usually very small, for example, 16 or 32 MB, and can only save a few photos in higher resolution.
In addition to these persistent memories, every digital camera also has a working memory. Immediately after a photo has been taken, it is initially in the working memory and is then written to the memory chip or the internal memory. Therefore, the size of the working memory is a decisive factor in the case of serial pictures, how many pictures can be taken per second, or which post-processing of the picture can be done with the camera directly after the picture has been taken.
Compared to an analog camera, a digital camera consumes significantly more energy. The consumption on the monitor is particularly high, which can, therefore, be switched off if necessary, but the lens, image sensor, and processing logic also require energy. If you take pictures with a flash, the battery will run out even faster. Therefore, the batteries of the cameras have a very short runtime for electronic devices – with most cameras, you will have to recharge the battery after about 200 to 300 photos. Therefore, a replacement battery is highly recommended for longer photo tours (this can be quite expensive for some batteries).
Today’s cameras are mostly operated with camera-specific batteries, which are included with the charger in the scope of delivery of the camera. Some cameras are also operated with standard batteries (mostly R6), in which case the battery life is often shorter. The camera-specific batteries are also lighter so that their use reduces the overall weight of the camera.
A battery can be recharged hundreds of times, but as the number increases, the capacity will gradually decrease. If a battery no longer achieves the desired performance, a new one must be procured (or a new camera – today’s batteries should last for several years without any problems). It should also be borne in mind that batteries are depleted more quickly in the cold. Therefore, a replacement battery is particularly important on winter photo tours, and keeping the battery warm can also make sense.
Each digital camera is equipped with various electronic connections so that the captured images can be transferred to another device.
Simple digital cameras usually have two ports: a USB port to connect the camera to a computer and an A / V port. The USB port is primarily used to connect the camera to a computer and transfer the photos to permanent storage. You can also connect the camera to other USB-compatible devices, such as a (photo) printer or digital picture frame. The A / V connector allows you to connect an A / V (audio/video) cable to connect the camera to a TV or monitor. The camera monitor will then be visible on the connected screen. Therefore, the A / V cable is ideal for the simple presentation of the photos taken or for better assessment, but the quality and resolution of an older television screen is usually lower than that of a computer monitor.
Some cameras also offer a mains connection to supply the camera directly with mains power. This is advantageous if you want to take more complex and time-consuming portraits or material shots and access a socket. Since most compact cameras are probably designed for mobile use, only a few have such a connection.
Other connections are often also available, for example, for a remote release and a flash sync connection.
The USB cable is usually always included – what other cables are included will be found in the product description. The connections are usually located on the side of the camera and are protected from dirt and moisture by a protective cover or cover.
Basic operating principle
The analog camera basically differs only slightly from the digital camera. It lacks the image sensor and a monitor; For this purpose, a light-sensitive film is inserted, which saves the pictures taken. The film is then transported for each new recording, either with a motor or with a hand crank. Fresh footage is used with every shot, while the digital camera always uses the same image sensor. While the pixels of an image sensor are arranged in a regular manner, the structure or grain of the film material is more random and usually makes it less uncomfortable at high magnifications. So here are the real differences to digital photography.
When taking a photo, the shutter opens for a fraction of a second (depending on the light available), just like with a digital camera. The light falls on the extremely light-sensitive film, the material of which experiences a chemical reaction and changes. One can say that each picture is initially black and gradually becomes white due to the light (so-called negative material). Where there is a lot of light on the picture, it quickly turns white. Where there is little light on the picture, it slowly turns white. As soon as the exposure time has expired, the shutter closes again, and the exposure of the image is completed. The photo is now ready, but the material is still sensitive to light, so the film is always kept in a light-tight environment.
Wherever a lot of light fell on the film, it turned quite white; where there was little light, it remained black or only changed to dark gray. In this way, black and white photos or actually gray value images are created.
In color photography, a film consists of several successive filter layers (red, green, and blue) that are only ever sensitive to certain wavelength ranges (just red, green, blue) and let the others pass. This creates a color photo. This principle corresponds to the mode of operation of the X3 image sensors already presented.
In the past, you had to manually rewind the film after taking it. Otherwise, you would have exposed the photo you had already taken again and “overwritten” it. Later, the cameras automatically rewound the film one place after the shot. When the last photo was taken, you also rolled it up automatically so that it was packed light-tight again and could not be damaged. With automatic rewinding, however, multiple artistic exposures, which demanding photographers sometimes want to deliberately carry out, were impossible – accordingly, many cameras have special buttons again to switch off rewinding.
Classic photo development in the darkroom.
The film is then developed in a photo laboratory and delivered to the customer in the form of a slide or paper image. In the case of negative material, further exposure is then carried out in order to obtain a paper print. With positive material, the brightnesses are equally correct and not inverted. Here the images are preferably projected as slides.
While the film itself is of exceptionally good quality, generally better than an ordinary 10 MP camera sensor, a lot of quality can, of course, be lost in development; Paper pictures, in particular, can be of relatively low quality with inexpensive production. Professional photographers, therefore, like to develop their photos themselves; on the one hand, to be able to ensure the quality of your prints yourself, on the other hand, to create artistic effects (you can still create the photo artistically even when developing it, even though it has long been taken by the camera). Since no further exposure takes place with slide films, but only the development, this proves to be a relatively robust variant in order to largely avoid quality losses by other people.
Although quality is always lost when the prints are made, computer technology also improved the development of photos in the 1980s. Even back then, programs could automatically refine the photo, for example, increasing the level of sharpness. Conversely, it has also happened quite often that these programs have destroyed the efforts of the photographer when it comes to prints when it comes to difficult motifs that the photographer was able to master, but not the automatic programs. One way out was either to make the slide film or to develop and expose the prints themselves.
The film has to be developed in complete darkness because even slight exposure to light would continue to expose the correctly exposed photo and quickly turn it completely white. In particular, the film must remain completely in the dark from purchase to use in the camera and development. However, since you cannot work properly in the dark, only the first step of development takes place in the dark. Here, the film is put into an opaque developer box. More precisely, it is wound onto a film spiral, which is then put into the developer box. The film spiral ensures that the film comes into constant contact with the developer. Since nothing can happen to the film in this can,
Now the developer is touched, which can be purchased. The developer is a chemical solution in which the film is developed. It is mixed in a concentrate-water ratio of 4: 1 (for example, 400 ml water and 100 ml concentrate) and should have a water temperature of around 18 to 20 ° C. The developer is always basic (pH around 8 or 9).
When it has been mixed, the developer is placed in the developer can, which must then be moved rhythmically (for example, the can tilts regularly). In this way, the developer should be balanced so that all photos are developed evenly. The more intense the movements and the warmer the water, the shorter the development time, but the more coarse-grained the photos become. It is, therefore, important to carefully observe the manufacturer’s instructions. This process already produces a visible image, but it is not yet stable.
As soon as the development time has expired, the developer is poured out, and then the stop solution is entered (stop bath/interruption bath). This bath has an acidic pH (4 or 5) and serves to neutralize the basic developer. The aim is to stop the development of the photo (which continues to advance in the basic solution). For some developers, however, the acid bath is not sufficient, and the fixation must be carried out immediately afterward.
The last big step is to add the fixer solution to the developer (fixer bath). As the name suggests, the film is now “fixed,” that is, it no longer changes in texture, no matter how much light falls on it. Depending on the substance used and the number of fixations already carried out in the water, the fixing takes between about 30 seconds and 3 minutes. After some developments, fixing water has been exhausted and must be replaced.
After the fixing bath, watering takes place. The film is now cleaned with clear water so that no traces of the fixing water remain. The cleaning must be done thoroughly and takes some time; the water has to be replaced several times.
The drying takes place last. The film strip is usually hung up vertically in a dust-free room or cupboard with clips. The development of the film is now complete. Subsequently, prints of the film can be made (paper pictures), or individual photos can be put into slide frames. In the latter case, slides are included that can be viewed using a slide projector.
Note: The procedure described is a fairly simple, modern procedure. However, the classic development of the photos took place in a dark room that was completely light-tight. This particularly affected the era of photography when large film plates (mostly glass plates) were still being used. In this dark room, there were the three baths developer bath, interruption bath, and fixing bath. These were usually three bowls in which the picture was then inserted (tweezers, for example, served as an aid). Since it was not possible to work in complete darkness, it was necessary to find a way to illuminate without disrupting the development process. Some emulsions were resistant to red light (long-wave light). That’s why red light was used in such chambers.
Comparison of analogue and digital photography
Digital photography has numerous advantages as well as some disadvantages compared to analog photography. This section will compare digital and analog photography, especially about their advantages and disadvantages.
As already mentioned, the analog camera takes a picture by striking light on a light-sensitive film and discoloring it. The photo must then be developed in a photo laboratory, and prints (positives) can be made. In digital photography, a sensor records the image and immediately saves it as a digital file.
The main advantage of digital cameras is that you can have the images assessed immediately after taking them. You can save an almost unlimited number of images with today’s memory chips, and you save film and development costs (and the development effort). Digital photography is therefore ideal for experimental photography, and for beginners – any number of photos can be taken and assessed without incurring major costs. Since no film is used, an “interruption” is also significantly less common (generally 24 or 36 photos in analog photography versus several hundred photos in digital photography, depending on storage capacity and battery life) – this is particularly important for underwater shots, photo- Shootings and series recordings noticeable.
A disadvantage of digital cameras also arises from this – once a sensor is contaminated or defective, it will continue to be used until it is cleaned or repaired. In the case of film material, the problem is usually already solved with the next shot or the next film. The film level of the analog cameras is also much easier to clean than the digital cameras’ image sensors. In practice, the entire camera is exchanged today if you are not satisfied with the image sensor’s quality. In analog cameras, the film material was exchanged, whereby analog cameras are usually even cheaper than comparable digital cameras due to the lack of a sensor and monitor.
Since digital cameras do not depend on any film, the ISO value and white balance can be set individually for each photo. In contrast, in analog photography, you have to set an ISO value and a color temperature beforehand.
Digital cameras use internal programs that can prevent various artifacts and optimize photos but can also ‘iron’ images, so they can ‘optimize’ at the expense of image resolution and contrast. Most digital cameras also offer many motif programs, which should help beginners in particular to take demanding photos, as well as video functions and sound.
If photos are to be used for presentations, e-mails, web applications, etc., digital photography is also convenient since the photos do not have to be scanned in then. This also makes post-processing easier. Unlike analog cameras, compact cameras can also be connected to television sets, mobile printers, etc.
Digital photos can be reproduced more easily and at no cost – the copy and the original are indistinguishable (copy without loss). This also makes digital archiving of the images easier. However, here again, there is the problem that storage media for digital data are not as durable as well-maintained negatives or slides. Archiving digital data, in turn, also requires continued copying. Just like before the invention of writing, you have to rely on a seamless transmission of information. Digital data cannot be left to rest for many decades. You have to deal with it every few years to preserve it for future generations. Another problem arises from the file formats used and the encoding and decoding of the same. In particular, if the formats are not international standards that cannot be interpreted by many programs, there is always the risk that such data can no longer be read on new computers, where old programs no longer work. The manufacturer or rights holder format no longer offers new programs. In practice, it has been shown that this represents a problem similar to digital data as the limited shelf life of the storage media. In case of doubt, it is not enough to simply copy the files to new storage media, if necessary, you also have to estimate how long the file format used will survive and then convert to another format in good time. If there are several versions of a standard for a format, most programs can only master one version, new programs rather than a new version. Therefore, it is not necessarily guaranteed that old documents that follow an old standard version are still displayed correctly with programs that follow a new standard version. The digital archivist must always be vigilant and well informed. That follows an old standard version that can still be displayed correctly with programs that follow a new standard version. The digital archivist must, therefore, always be vigilant and well informed. That follows an old standard version that can still be displayed correctly with programs that follow a new standard version. The digital archivist must, therefore, always be vigilant and well informed.
Unlike digital cameras, analog cameras are less prone to noise in the dark because they do not have a sensor that heats up (however, noise also occurs in films with a high ISO value). However, the sensor technology used has a greater potential to achieve higher sensitivities; the so-called quantum efficiency of image sensors tends to be much higher than that of film material. Due to the construction of the sensors and the adjacent color pixels, the full potential of this technology is far from being used, while the film technology is exhausted.
The entry costs to digital photography are higher, even if they have become profitable over the years. Digital cameras in the lower price category also seem to have a lower ‘meantime to failure’ than analog cameras. However, due to the progress in image sensor technology and other improvements or efficiently advertised changes to new camera models, the need for a new camera is often quickly aroused anyway, which in turn can lead to the cost per image for digital cameras being similar to the running costs with analog cameras. Also, the battery life of digital cameras is significantly shorter.
Image quality is better in analog photography since even 12 MP sensors cannot match the resolution of 35 mm film, let alone medium or large format. Analog photography has advantages for high-resolution large-screen recordings or large enlargements, especially since it is also very easy to switch to a film optimized for the respective application. You will not be able to see any pixels even at the highest magnification since the silver crystals (“pixels of analog photography”) do not have a square but irregular shape. Instead of the pixels, we see the irregular, random distribution of this grain instead of regularly arranged pixels. This is usually perceived as significantly less disruptive artifact.
Digital photography can lead to mass photography. As a result, you may lose track of photos. Since you no longer have to worry about failed pictures, it can also happen that the classic principles of photography, such as exposure, focusing, and composition, are neglected (many snapshots in digital photography compared to few, but better quality photos in analog photography). However, this also offers a chance to experiment and get good results through trial and error. It would be very tedious with the analog cameras because one cannot look at the results immediately after the shot. The mass photography related to digital photography also leads to mass, Partly hardly manageable publication of photos. However, since the ‘truth’ or the ‘core’ of a motif can often not be immortalized in a picture, long series of photos with different images of the same motif naturally offer the viewer an opportunity to learn more about the motif than if he was forced to do so would be to follow the photographer’s point of view with just one shot.
Incorrect operation of digital cameras can be more devastating than in analog photography. All pictures can be completely deleted on digital cameras with just a few clicks. Storage and formatting errors, as they can occur in principle, can also destroy the recordings made. In analog photography, this problem occurs less with properly inserted film, at most when the camera housing is opened. The many setting options can also overwhelm users or lead to undesired settings (for example, a low resolution, a high ISO value) being made or maintained accidentally. The familiarization with the functioning of a digital camera is, therefore, much more complex.
Analog photography partly has its styles for artistic design and post-processing (e.g., multiple exposures or color design during film development). Although digital photography and digital post-processing make this possible, these are two completely different techniques with different advantages and disadvantages.
Compared to digital compact cameras, there are a few more advantages of analog photography: Contrast and color dynamics are usually greater.
Types of cameras
The compact camera is a small, handy camera in the lower or middle price sector. Simple models start at around 40 euros, but good models can cost up to 300 euros. Compact cameras can be analog as well as digital cameras. Today, digital cameras are mostly offered in stores.
With compact cameras, the focus is on robustness, small dimensions, small volume, lightweight. Since the cameras should be particularly flat, there is often only limited optical zoom (usually three or four times). Most of the time, a very small, faint lens is extended to the front before pictures can be taken. Compact cameras are entry-level cameras; They usually offer little manual setting options (such as exposure, aperture, ISO value, manual focus, etc.), but have numerous pre-made programs and help, so that beginners and even children can easily take photos. The general setting options such as focal length, aperture and exposure are often limited;
Due to the compact design, the image sensors used in digital compact cameras are usually very small and have only relatively small pixels. Such cameras are not particularly sensitive to light and often work at the diffraction limit due to the weak lenses.
The terms compact camera and 35mm camera (KB camera) are very similar. The term 35mm camera refers more to the film format, while the compact camera refers to the size of the camera.
Bridge camera ]
Typical bridge camera.
The bridge camera (also: Prosumerkamera, sometimes hybrid camera) is technically between the relatively simple compact camera and the rather complex, sophisticated system camera. On the one hand, it is still quite handy and only slightly larger in volume than conventional compact cameras, but the performance range often comes close to that of simple system cameras. The advantage of these cameras is that you have the opportunity to take sophisticated pictures. However, at the same time, the camera is still relatively small and, like the compact camera, is well suited for on the go.
Often a higher quality, more powerful optics is installed, which also has a larger zoom range. Compared to the 35mm format, the built-in image sensors are also small.
System cameras ]
System cameras are cameras that consist of a housing and a large number of interchangeable accessories, in particular interchangeable lenses.
Mirrorless system cameras
Compared to SLR cameras, mirrorless system cameras (DSLM, Digital Single Lens Mirrorless) replace the optical viewfinder with digital video cameras with a monitor and an electronic viewfinder (EVF, English: electronic viewfinder). A smaller image sensor is generally used. This enables a more compact design than with SLR cameras.
Provided you can do without the advantages of an optical viewfinder and the high sensitivity of large sensors (with the same design, a large sensor has more light proportional to the area) and equipment with less weight and volume is preferred, without in particular wanting to do without interchangeable lenses System cameras can already be a sensible choice.
In such a system, it is possible to combine different lenses, flash units, and cameras to be able to use good equipment depending on the shooting situation. This usually makes the camera less bulky, while at the same time having high performance. The only disadvantages compared to compact cameras are the significantly higher purchase costs, the higher weight, and the more or less complex changing of accessories.
Digital SLR camera
Typical SLR camera.
The essential feature of the SLR camera (often also SR camera or SLR / DSLR, English: digital single-lens reflex) is, as already mentioned, the advantage that you can see exactly what the camera will record in the optical viewfinder. Also, there are cameras with large, light-sensitive sensors such as the small format or the medium format practically only as SLR cameras. Like the other digital cameras, digital SLR cameras with “Live View” also have a monitor as an electronic viewfinder. Older digital SLR cameras only use the monitor to view already saved images and to display the camera settings. With modern digital SLR cameras, the photographer can choose if necessary.
The image sensors are available in SLR cameras in different sizes, at least always larger than with compact cameras and usually also larger than with mirrorless system cameras. Manufacturers usually offer the cameras so that you can buy lenses from the outset that can be used with small and large image sensors. If necessary, you can easily switch from a camera with a small sensor to a 35mm format to achieve higher sensitivity or resolution.
Even if the mirrorless system cameras have caught up with the available lenses, there is a hard-to-see range of accessories for the established SLR cameras. It should be noted that there are significantly more accessories for the analog SLR cameras for special branches of photography until around the end of the last century so that there are always instructions on how to use old accessories on new cameras to optimize areas to cover that are no longer the focus of commercial interest of manufacturers.
SLR cameras usually offer a variety of manual setting options and professional (expandable) equipment, often with super wide-angle or super celebrity focal lengths, higher-quality image sensors, flash units, better lenses, etc.
If you want to exploit their full range of functions, SLR cameras are usually somewhat more difficult to operate than the simpler cameras. But if it is not a professional model, they have similar motif programs and automatisms as the other cameras. If you like, you can rely on the automatic system and only benefit from the optical viewfinder, larger image sensor, and more extensive accessories. Since these systems are designed for large sensors, the equipment becomes significantly heavier and more voluminous, which can be a burden during transport and result in a calmer camera position during actual photography. Of course, they enable higher quality recordings and are particularly excellent for creative and experimental recordings. However, an SLR camera is also quite expensive; the lowest models usually start between 300 and 400 euros, but professional SLR cameras can go far into the four-digit range. Of course, the not inconsiderable costs for the high-quality interchangeable lenses, powerful system flash units and other accessories such as a suitably stable tripod designed for the weight of such a camera with a large lens, must also be added. The price of a simple lens or a usable tripod often exceeds that of a compact camera or bridge camera. Of course, the not inconsiderable costs for the high-quality interchangeable lenses, powerful system flash units and other accessories such as a suitably stable tripod designed for the weight of such a camera with a large lens, must also be added. The price for a simple lens or a usable tripod often exceeds that for a compact camera or bridge camera. Of course, the not inconsiderable costs for the high-quality interchangeable lenses, powerful system flash units and other accessories such as a suitably stable tripod designed for the weight of such a camera with a large lens, must also be added. The price for a simple lens or a usable tripod often exceeds that for a compact camera or bridge camera.
Medium format cameras and large format cameras
Medium format camera.
Medium format cameras are cameras that have a significantly larger recording format than compact cameras. The edge length of the film or image sensor is approximately 4 to 10 cm, enabling a higher sensitivity or resolution. Typical medium formats in analog photography are, for example, 6 cm x 6 cm or 6 cm x 7 cm. The relatively large size results in long focal lengths and thus a high weight. For this reason, medium format cameras are particularly suitable for working in the studio or when the equipment is transported to a specified location. The complete equipment would be a bit difficult in the long run for hikes and long walks.
Medium format cameras are often system cameras (and often also SLR cameras). Still, their accessories are limited because there are fewer buyers for the rather expensive cameras than for the SLR cameras in 35mm format. However, with some cameras, it is possible to swap the back of the camera to switch from film to digital image sensor and back. So it is not necessary to change the complete system. It is, therefore, also possible to change the sensor to a higher sensitivity or resolution.
Large format cameras use even larger formats, mostly 12.5 cm x 10 cm, 25 cm x 20 cm, or individual film plates. The resolution and the focal length of the object are correspondingly larger. Large format cameras were mainly used in the early days of photography.
Special cameras are camera types that are mostly used for a very specific purpose or are used in a very specific area. They are generally special forms of the types of cameras listed above.
Some examples are:
- Disposable camera:35mm camera that already contains a film at the beginning (usually 27 pictures) and can only be used once. When the film is full, the entire camera is handed over to the laboratory. The disposable camera is very inexpensive and mostly extremely simple (mostly fixed focal length, hardly any manual intervention, no flash, etc.). It offers itself as an “emergency solution” if, for example, you have forgotten your camera (on vacation, etc.), as a backup camera (for example, in the car) or for children, to whom you may not want to entrust high-quality photography equipment. With the introduction of inexpensive digital cameras, the disposable camera was largely replaced.
- Instant camera: This camera is equipped with photo paper and chemicals and immediately creates an image after taking it. The Polaroid camera was probably the best known instant camera. Your advantage that you get an image immediately (even if only in low quality) gradually faded with the rise of digital photography.
- Underwater camera: Special camera to take underwater pictures. There are also underwater housings for several cameras to buy so that they can be used as underwater cameras.
- Mini cameras: cameras of minimal dimensions, mostly used for espionage and secret service purposes.
- Stereo cameras: cameras for taking 3D images or images with a 3D effect.
- Panorama cameras this type of camera offers a very wide angle of view (for example 120 ° or more) to be able to take panorama pictures. Some panorama cameras also have a rotating head that enables 360 ° shots.
- Special versions without a protective filter for astrophotography – often, the photographer would like to determine which wavelength range his camera is sensitive to. Built-in infrared or UV filters are rather undesirable, partly also the possibility of color recordings, because this costs sensitivity.
- Special cameras for infrared images – because the usual sensors are also sensitive in the infrared range, it is often sufficient to install other filters in the image sensor.
Several devices are not primarily made for photography, but often have a photo function:
- Mobile phone: These often contain a camera function today, but mostly with a low resolution, fixed focal length, and very few setting options. They are designed for snapshots and everyday shots. Few offer higher resolutions and fairly good quality for everyday use.
- Webcam in the notebook: Most notebooks today have such a camera installed, in addition to videos with a modest resolution, recordings with a modest resolution can also be taken. In some cases, even the monitor of the computer is set to maximum brightness as a light source for recording. Thanks to the direct connection to the computer, such images can be distributed practically in real-time.
- Digital camcorders: Digital camcorders are actually used to create videos, but they also allow you to take individual photos. The quality of the photos is significantly better than that of a mobile phone, but one problem is that camcorders often only use low to medium pixel counts and small sensors (approx. 1 to 4 MP).
- Digital microscopes depending on the model, offer the possibility of capturing very small objects with a very small sensor. Some of them can also be used to take ‘normal shots’ of more distant subjects.
Choosing the camera
If you want to buy a camera, you first have to know what expectations are placed on the camera, i.e., what the camera should ultimately be used for. The entry-level models of the compact cameras are probably already a useful solution for snapshots and easy shooting. The acquisition costs are low. The operation is simple; the quality is usually sufficient, especially if the pictures are only rarely or not viewed again. If you want to experience photography creatively or try out the theoretical knowledge conveyed in this book, you can choose a compact or bridge camera with more manual setting options. Compact cameras in the middle and higher price range often offer this;
Statistically speaking, most good photos are currently taken with digital SLR cameras. They offer the best technical picture quality about the price.
The following table gives a rough overview of a compact camera’s evaluation parameters in the different price categories. All information is only a guideline since the individual models in the individual price ranges are very different.
Target from the user’s perspective
Lower price range
Higher price range / bridge cameras
As cheap as possible.
40 to 100 euros
100 to 200 euros
Over 200 euros
As high as possible.
4 to 12 MP, sometimes up to 24 MP
12 to 24 MP
16 to 50 MP
As big as possible.
~ 2 microns
~ 2 microns
As big as possible.
1 / 3.2 “
2/3 “, Four Thirds, Foveon (see above)
As small as possible.
Very small to small
Small to medium
As big as possible.
Small to medium (sometimes large)
Medium to large
As big as possible. °
Mostly 3 times, sometimes 4 times
3 times to 5 times, occasionally higher
3-fold to 14-fold; often 8 times or higher
Lowest focal length °°
As low as possible
mostly 32 to 38 mm
mostly 28 to 38 mm
usually 24 to 35 mm
Largest focal length °°
As big as possible
~ 100 mm
~ 200 mm
~ 300 mm
Maximum exposure time:
As long as possible
Usually 1 to 2 seconds
Usually between 2 and 30 seconds, depending on the model
As big as possible.
Usually between 2.8 and 5.6, sometimes up to 8.0
Manual setting options
Very little; Flash, format, resolution, focus, possibly filter
Little to much: flash, format, resolution, filter, exposure, aperture, ISO value, exposure compensation, focus, exposure metering etc.
As much as possible.
Tripod, strap, memory card etc., but otherwise usually no accessories
Tripod, strap, memory card etc., sometimes additional flash unit, underwater housing
However, a large zoom range usually reduces the imaging quality of the lens
°° The ‘equivalent’ to the 35 mm format
The simpler compact cameras can hardly be compared with system cameras or SLR cameras due to the interchangeable optics and the significantly larger sensors. In principle, you have to finally ask yourself the question of whether you are ready to move around the area with extensive accessories and then invest to a greater extent to be able to dig deeper into photography. Either way, the complete beginner usually has a lot to gain experience with a compact camera or a bridge camera at a relatively low cost. Then it usually quickly becomes clear whether it is worth buying more extensive equipment, which motifs are preferred, and which equipment is well suited for it. And even if you get all the equipment later,
A useful criterion for assessing the right equipment can also be how many pictures you intend to take per year or have already taken it in previous years. If it takes a few years to get the cost per picture under one euro, you have probably bought equipment that is too expensive.
There are certain accessories for each camera that can be purchased separately; some of the available accessories are sometimes included in the scope of delivery. Some accessories are presented in this section. Standard accessories such as a tripod, bag, and memory card can be purchased for every camera. Special accessories, however, are only available for cameras in the medium and higher price range.
Since digital cameras have a very high energy consumption, it is usually best to buy a replacement battery and take it with you on photo tours. When traveling, you should never forget the corresponding charger, as a camera-specific charger will be difficult or impossible to find while traveling.
For SLR cameras, in particular, there are also so-called battery handles that are mounted on the camera and which then make it possible to use additional rechargeable batteries or batteries for energy supply. This often eliminates the need to change the battery even during long and intensive photo sessions. The battery handles – hence the name – also offer improved grip comfort, especially for portrait format shots, and usually a separate trigger on this handle.
Although today’s memory cards have a relatively high capacity, it can also make sense to take a second card (replacement card) with you on intensive photo tours. There are also mobile hard drives for travel, which are often specially designed for photographers (“image tanks”). These usually offer several 100 GB of storage. Alternatively, there are also mobile DVD burners, so that photos can be burned to DVD on the go – however, this is correspondingly more complex with a smaller capacity. If you have an MP3 player with sufficient capacity, you can also use it as temporary storage.
When traveling, it is also good to take an A / V cable with you so that you can view the photos on a television. If you take a laptop with you anyway, you can transfer the photos directly to the computer with the USB cable and edit and archive the photos before you go home.
In the specialist trade card readers are also offered, which read the data directly from the memory card and transfer it to a computer. Some computers also have integrated card readers (usually only for SD cards) – however, transferring the photos using a USB cable is hardly more complicated. Still, problems can arise due to communication problems between the camera and the computer, depending on the protocol, operating system, and program used, which is why the relatively inexpensive card readers are often the better choice. Care should only be taken that the type of connection matches that of the computer to enable a maximum data rate.
Lenses for different focal lengths
Especially SLR cameras, system cameras, and medium format cameras offer different interchangeable lenses, which means you can unscrew the lens and replace it with another lens. There are lenses with different focal lengths, i.e., (super) wide-angle lenses, normal lenses, and (super) telephoto lenses. These can also be available with different light intensities and in different execution quality. There can also be lenses for special applications.
Fisheye and super wide-angle
Space is taken with a fisheye lens – The imaging properties typical for this type of lens can be seen, especially at the edges.
The fisheye lens is special. It often has a focal length below a super wide-angle lens, usually 8 mm to 15 mm. With a fisheye lens, angles of view of approximately 180 ° can be recorded.
Since with super wide-angle lenses and even more with fisheye lenses, a very large image angle is to be imaged on the built-in, flat image sensor. This extreme type of imaging always results in imaging properties that deviate significantly from our normal viewing habits. In the case of a fisheye lens, the task is obviously to map a plane of focus of infinite extent onto a flat image sensor, which is finally far away from the lens. Even with super wide-angle lenses, the recorded angle of view must be extremely compressed to be imaged on the image sensor.
Different imaging methods are implemented for the two types of lenses to meet these requirements. With the fisheye lens, an attempt is made to reproduce as closely as possible. Objects with the same area at the same distance but from a different angle of view should also be displayed as large as possible. This leads to the characteristic effect that straight lines of the motif are mostly depicted on arcs. So the image looks curved. On the other hand, the image is attempted to be implemented with a super wide-angle in such a way that parallel lines that run in the plane of focus or a plane parallel to it are also represented as parallel lines. This usually leads to the effect that objects are displayed wider (or higher) at the edge of the picture than in the middle of the picture.
Depending on the lens construction, there may also be a mixture of both types of illustration. An attempt is then made to reduce both effects, in which case one inevitably gets to see something of the effect of the other construction type.
There are fisheye lenses that only have a picture angle of 180 ° over the diagonal. These are called full-frame fisheye lenses. For the 35mm format, these have a focal length of about 15mm. The other type shows an image angle of 180 ° in each direction, so a circular image is created. The rest of the picture then remains black and unexposed.
There are also special designs, for example, from Nikon, which have a viewing angle of well over 180 °. Canon has a fisheye zoom lens. In the 35mm format, you can zoom from the full format to the round image. With the smaller image sensors, you can at least select the appropriate focal length for the full format.
Not all additional lenses aim to offer a special focal length. Luminous lenses are, for example, lenses that have a very small aperture value (for example, 1.2 or 1.4 for a normal lens). This enables you to take pictures at dusk without the need for a tripod. They also allow extremely fast shutter speeds under normal lighting conditions, so that all kinds of movements can be frozen. Due to the small aperture values, they also allow you to work with selective focus. However, it is structurally very difficult to realize lenses with light intensities such as 1.0 or 1.2, which offer a high resolution when the aperture is open.
Shift lenses make it possible to record a shifted image section. It often happens that, despite a wide-angle, it is impossible to fully image a building and then usually point the camera upwards until it appears completely on the image. This creates a perspective distortion, which is expressed primarily in falling lines. With the shift lens, the front lens groups can be moved up or down. This makes it possible to map such a building “normally” without the appearance of falling lines.
Tilt lenses make it possible to work with focus levels that are not parallel to the image sensor. For this purpose, the front lens group is tilted relative to the axis to the image sensor. Flat motifs, arranged at an angle to the shooting direction, can be reproduced consistently in this way, if necessary, even with the aperture open. If you tilt in the other direction, an effect similar to selective sharpness can be achieved in reverse.
Usually, both functions Tilt and Shift are offered in the same lens. For medium format cameras, in particular, this is sometimes also achieved with bellows devices, where the lens and camera can then be pivoted and moved independently of one another. The extension of the bellows device then determines the focus.
Macro lenses make it possible to focus on objects at close range. They usually offer an image scale of 1: 1 (more on that later). An extreme form is a magnifying lens with an extremely large extension, which enables even larger magnifications.
Special lens accessories
A wide-angle converter is a type of lens that is attached to an existing lens. It enables lower focal lengths. A factor indicates how many times the focal length is reduced. A 0.5 wide-angle converter, placed on a 28 mm lens, produces a focal length of 14 mm. Accordingly, there is also a teleconverter, which extends the focal length. Here a factor of 2 would mean that a lens with a focal length of 35 to 140 mm is converted into a lens with a focal length of 70 to 280 mm. The quality of the images with such converters is, of course, limited. Therefore, the wide-angle converters are rather not an option for systems with interchangeable lenses, especially since the converter must always be optimized for the respective lens to deliver useful results. Bridge camera vendors occasionally offer such converters for specific cameras.
Teleconverters are also available for systems with interchangeable lenses. Of course, the quality of the images also varies from supplier to supplier. It does not necessarily have to be optimal from the lens’s supplier if the converter is not specifically tailored to a specific lens. In general, there is always a loss of quality when using such converters. However, because the converters are relatively small and inexpensive, they are often used when you only occasionally need a very long focal length. The effective light intensity is increased proportionally to the teleconverter’s extension factor, which can influence the function of the autofocus.
As an alternative to macro lenses, there are also close-up lenses that are screwed onto the lens like a kind of magnifying glass, as well as intermediate rings or bellows devices that are inserted between the lens and the camera housing; all variants also allow a greater magnification than that offered by pulling out the lens alone.
The close-up lens must be selected to match the lens, both in diameter and focal length. Achromats can usually be used here since simple individual lenses usually lead to significant color errors. The close-up lens as optics always has its lens defects; therefore, it rather influences/deteriorates the imaging quality. Therefore, a macro lens is certainly the better choice in terms of quality, which is why close-up lenses rather allow entry into macro photography or make sense for compact cameras where the lens cannot be changed.
On the other hand, intermediate rings only extend the pull-out, so they do not have their lens defects and do not directly influence the image quality. Therefore, the rumor persists that the image result depends only on the extension of the respective intermediate ring, but not on the processing of the product. However, if the connection is rickety, the optical axis is no longer correct. However, more influence can have if stray light is generated in the intermediate ring by reflection and falls on the sensor. This is highly dependent on the processing of the product, and such stray light can make pictures completely unusable so that it can have a great influence on the image result. Experienced manufacturers will, therefore, rely on sufficiently large inner diameters and stray light traps and stable design, to be able to offer usable intermediate rings. Correspondingly voluminous and equipped with scattered light traps are also good bellows devices. There are also models in which you can specifically tilt the optical axis to achieve special effects. However, the bellows are more sensitive to mechanical stress and can hardly be used without a tripod due to their size and handling.
So-called turning rings follow another approach. With lenses of ‘normal’ design – which generally does not include the design of super wide-angle lenses – it may be useful for macro shots to turn the lens around, especially if the distance between the subject and the lens becomes smaller than that between the lens and the sensor because then the imaging performance of the Lens for such close-ups increases. Due to the small distance to the subject, there is usually a large image scale. This procedure does not make sense for macro lenses or magnifying lenses because they are already optimized for the close-up range. To mount suitable lenses upside down on the camera, the reversing rings are required. In the simple variant, an adapter is required to be connected to the camera on one side and the filter thread of the lens on the other. All connections of the lens then look at the subject, so all settings must be made manually. In a more convenient variant, an additional adapter is placed on this connection side and connected to the adapter on the camera so that the lens is completely connected to the camera again, and an automatic system can be used. Problems with this approach are that the subject can easily be shaded by the lens, and this side of the lens, including the connections, is not designed to be exposed to normal environmental influences on the subject side. Therefore, this approach is rather to be understood as an inexpensive entry into the field of high magnifications.
Masks are lens attachments that ensure that the image no longer appears rectangular but assumes a certain shape (for example, heart, circle, key, etc.). The rest of the picture is then black. Such mask effects can also be created with some digital image processing programs or, with a little skill, you can also make them yourself.
Filters are special lens attachments that achieve a certain artistic effect or that simply filter out unwanted wavelengths from the light. Such filters can also often be created afterward with image processing programs, but not without exception. Some filters create a remarkably artistic impression, while others only make subtle changes. If a photo is taken with a filter, the exposure time must always be increased, since each filter means that less light falls into the lens.
Long exposure is sometimes necessary to express movement. Exposure times between 1/8 and 1/30 seconds are usually used to photograph waterfalls, but in daylight, this would severely overexpose the image. The gray filter helps here.
Known filters are:
- Gray filter (ND filter): A simple filter that reduces the amount of light entering. This is used when, for certain reasons, you are aiming for a longer exposure time (for example, to hold on to movement or to give less weight to normal daylight when taking flash pictures). Using a large f-number and low light sensitivity (ISO) is sometimes a certain alternative. If you don’t have a gray filter on hand – you won’t be able to get around such a filter in different situations on days that are too bright. An extension factor X usually characterizes the ND filter. This indicates in ratio 1 / X how much light the filter still lets through or how many exposure steps X the image is darkened. ND-8 means that the filter is only 1/8 of the amount of light (12, 5%), and the image must now be exposed eight times longer for correct exposure (e.g., 1/25 second instead of 1/200 second). Analogously, this means that the image is darkened by three aperture stops (3 aperture steps are two ^ 3 = 8 exposure steps).
- Polarization filter (polarizing filter): a filter that eliminates or reduces reflections on smooth surfaces, window panes, water, etc. It is also possible to make a cloudless sky (e.g., when taking landscape pictures) appear darker and, therefore, blue. In the case of incident unpolarized light, the amount of light is consequently reduced by half, with polarized light depending on the polarization between 0 and 100%. Therefore, the polarization filter can be rotated relative to the lens in such a way that only the desired direction of polarization is let through.
- Star filter: a filter that transforms point light sources in an image into stars. This is particularly useful for creative night shots in cities.
- UV blocking filter (haze filter): Prevents an excessive blue cast in the mountains or the coastal area by reducing the UV light. The filter or the lack of it can also have astounding effects on the flowers of plants. Digital cameras do not need a UV cut filter.
- IR cut filter: According to the UV filter, the light’s infrared portion is reduced here. In reverse, some filters only let infrared light through and block visible light. Depending on which filters are already in the camera in front of the image sensor, different effects can result. If the camera itself does not have an IR cut filter, you can also take infrared pictures with the image sensor, if you block the visible light, upside down the IR cut filter ensures that the image sensor does not pick up hot or warm objects as striking red.
- Gradient filter: a filter that is half colored. The other half is transparent and does not affect it. Gradient filters are mainly used in landscape photography to give the area below or above the horizon a different color or brightness.
When buying a filter, you first have to check whether your camera has a filter thread (that is, whether it can be screwed on or attached). Furthermore, the lens diameter or the filter thread diameter of the lens must be known. This is usually in the manual or on the lens (for example, 58 mm). Then only filters can be used that have this lens diameter. Since filters are often quite expensive, you should also consider carefully which filters you want to use or consider useful – each filter has a certain advantage in some way.
In most cases, you can get by without a filter and can do it of digital image processing and simulate the effects of some filters afterward. Larger filters can also be easily screwed onto lenses with smaller diameters using inexpensive adapters. In reverse, the image frame is darkened by the filter mount. For wide-angle lenses, there are also special filters with a frame with a very low profile to avoid shadowing. With special lenses, there may also be plug-in filters or foil filter holders, then the filter is housed in the steel passageway and not screwed in front of the lens.
For some cameras, additional flash units are offered, which are more flexible and, above all, more powerful than the standard flash units installed in the cameras. If no additional flash units are offered for a camera, there are external flash units on the market that trigger the built-in flash of the camera.
Remote triggers are offered on some cameras to allow triggering from another location. They are available as a cable release (here there is a direct connection to the camera and the trigger on the camera is activated at the push of a button), electronic release via cable, infrared release and radio release. Mechanical tripping triggers are often used in mechanical, analog cameras. Electronic triggers are used on cameras that have a microprocessor to process the trigger signal. Infrared triggers react to an infrared signal and radio triggers to radio signals. Due to the significantly different wavelengths of the signals, radio signals usually work over larger distances and corners.
The remote release allows more freedom than the self-timer – the photographer can trigger in an unobserved moment and thus has a better opportunity to take authentic or unglazed pictures. When taking pictures of animals, there is also the possibility of positioning yourself independently of the camera’s location so that the animals to be photographed are not disturbed by their presence.
For camera monitors, screen shutters are available from specialist retailers that darken the screen in strong sunlight so that it can be seen better. However, the image quality of the display has improved enormously in recent years, so that you will usually get by without additional screen bezels.
The lens hood is another well-known accessory(also: lens hood, sun visor), which is particularly important for larger lenses and is sometimes included in the lens’s scope of delivery. The shape and size of the lens hood depend on the lens diameter and the focal length. Unsuitable lens hoods either do not optimally reduce the lens flare or lead to edge shading of the image. At first glance, the lens hood is reminiscent of a filter, but the opening is completely free so that it is not counted among the filters (although it is attached to the lens like a filter). It is particularly recommended for use in sunlight, wherewith larger lenses sidelight can fall on the film or image sensor, leading to unsightly colored circles or rings and making the image appear dull and less contrasting. The often-used term “lens hood” is misleading from a photographic point of view since the lens hood prevents artifacts from sidelight – it does not have the desired effect indirect lens shots (for example, sunsets). Also, it offers no protection for light reflections caused by light sources within the captured image.
Tulip-shaped lens hood.
Length plays an important role in lens hoods. The smaller the focal length, the shorter the lens hood must be to prevent shading (vignetting). Otherwise, the image would become darker towards the edges since the lens hood, which is too long, would, to a certain extent, cast shadows on the edge of the image. Larger focal lengths require longer lens hoods to protect against the light effects effectively. To avoid vignetting, lens hoods for zoom objects are always designed for the smallest focal length. At longer focal lengths, their protection may no longer be optimal, but it will not create shadows.
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