# Digital camera

A digital camera, above with a view of the image sensor (without lens), below with a lens (left) and with a view of the screen on the back of the camera (right).
Back of a digital camera showing the picture to be taken as a preview (Live View)
Structure of a digital mirrorless system camera, here using the example of a disassembled Sony Alpha 7R

A digital camera is a camera that uses a digital storage medium as a recording medium instead of a film (see: analog camera ) ; the image is digitized beforehand using an electronic image converter ( image sensor ) . Some film cameras can be converted into a digital camera with a digital rear wall .

## history

Cross-section of an Olympus E-30 DSLR from 2008

### Invention phase

The history of the digital camera begins in 1963 with the video disc camera invented by David Paul Gregg while at Winston Research Corporation . Although her pictures could only be stored for a few minutes and electrically analog (on that video disc), it is the first camera that could electronically save still images.

The first patent for an image sensor (in the form of a matrix of discrete photodiodes , each coupled to a storage capacitor), which can record and store optical images through the use of (solid) semiconductor components ( solid state device ), was applied for in 1968 .

In 1969, Willard Boyle and George Smith invented the basis of the CCD ( charge-coupled device ). A CCD, originally developed as a data storage device, is a light-sensitive chip that can be used to store images for a short time. This invention was the ultimate technical breakthrough on the way to digital photography. In 1970, Bell Laboratories scientists built the first solid-state camera to use a CCD as an image sensor. It was still an electric-analog video camera with a live image , as it was not possible to reproduce a single image permanently due to the lack of buffer memory or even to save several images in a sequence and then reproduce them.

In 1972, Thomas B. McCord of MIT and James A. Westphal of CalTech invented and built a digital camera. While your camera used an analog vidicon image pickup tube with a 256 × 256 pixel matrix (0.065 megapixel), it wrote 8-bit digital image data in about 4 seconds on a 9-track, magnetic digital cassette. They published isophotic images of Jupiter and the globular cluster 47 Tucanae, taken at the Cerro Tololo Interamerican Observatory in Chile in 1971. Their report was submitted to Applied Optics on October 12, 1971 and published in March 1972.

McCord and Westphal's “digital camera” weighed 10 kg and had the approximate dimensions of 20 × 20 × 40 cm. The electronics and the cassette recorder were installed in a 53 cm equipment cabinet and connected to the camera by a cable. So it was a stationary, corded system. McCord and Westphal filed a patent (US3951552) for their digital camera on August 7, 1972, which was granted on April 20, 1976. The digital camera was shown to the public for the first time in late August 1971 at a conference in Santa Cruz, California.

Another patent was filed in 1972 by Willis A. Adcock of Texas Instruments . It describes a filmless, electronic camera, whereby a TV screen is recommended as a viewfinder.

CCDs developed and produced by Fairchild Imaging were commercially available in 1973. The resolution was 100 × 100 pixels (0.01 megapixels). However, the first CCD camera marketed was a television camera built by Fairchild in 1973. The MV-100 model used a Fairchild image sensor with 0.01 megapixels and was primarily suitable for surveillance systems, medical technology and industrial applications. It weighed only 170 grams, and the electrical power consumption was only one watt . In 1974, Gil Amelio found a way to manufacture CCDs easily and industrially. 1975 was the year of birth of the first “portable” digital camera. It was designed by Steven J. Sasson from Kodak . Using the Fairchild CCD as an image sensor, it took 23 seconds to store a single image on a digital cassette and weighed over 4 kg.

### Further development

Development of the new compact cameras with zoom lenses from 2004 to 2017

From the end of the 1980s, digital cameras were primarily used by professional photographers in the field of studio , fashion and advertising photography and, from the mid-1990s, also in reportage photography . Early series-ready models were offered by Apple ( Apple QuickTake ), Casio ( QV-Series ), Kodak (DCS), Sony ( Mavica ) and Canon ( Powershot ); Konica Minolta ( Dimage ), Nikon ( Coolpix ), Olympus ( Camedia ) and others followed with their own model series. In 2002, Kyocera presented a digital single lens reflex ( DSLR ) camera with a sensor in full 35mm image size ( Contax N Digital ) for the first time. There is now an unmanageable abundance of models in all price ranges and equipment levels.

In the home user sector, digital cameras have become increasingly popular and, due to rapidly falling prices, have achieved higher sales figures than analogue photo devices since around 2003. Many manufacturers have now completely stopped or greatly reduced the production of analog models.

There is a high rate of innovation in computer technology (and the associated digital photography). New devices are considered obsolete after just a few months, which resulted in a strong revival of the entire photo trade, which was considered saturated and technically exhausted before the introduction of digital cameras.

#### New camera systems

In the course of digitization of the cameras, new camera housings were initially often adapted to the old camera systems , in that the lens connections and lenses were retained despite the reduction in the effective image circles . In 2003, Olympus introduced the Olympus E-1, the first SLR camera of the Four Thirds standard , which was developed from the ground up and specifically for digital photography. This cross-manufacturer standard was further developed in 2008 with the first mirrorless camera housing with electronic viewfinder , the Panasonic LUMIX DMC-G1 , to the Micro Four Thirds standard . Many other suppliers of system cameras have become proprietary digital camera systems released for such mirrorless cameras such as Sony NEX , Samsung NX , Nikon 1 or Canon EOS M .

#### Increasing the image resolution

The development over time of the maximum number of pixels in digital amateur cameras between 2000 and 2012: After stagnation at eight megapixels from 2003 to 2005, the number of pixels began to increase again, which has reached a new plateau at 24 megapixels.

In 2000, the Olympus E-10, the first amateur camera with an image resolution of four megapixels, was brought onto the market. In the following years, the image resolution for such devices was continuously increased and in 2011 often reached 16 million pixels, in individual cases even 24 million pixels, such as the Sony Alpha 77 .

Since around 2007 it has been pointed out again and again that increasing the number of pixels can be detrimental to image quality . In 2012, Nokia even presented a smartphone , the Nokia 808 PureView , whose camera is equipped with a 41 megapixel image sensor, which was also criticized for its high number of pixels.

#### Increasing the zoom range

The zoom range of digital cameras with built-in zoom lenses between 2004 and 2017.

After many compact cameras were still equipped with a three-fold zoom range up to 2004 , the maximum available zoom range continued to increase over the years. An extreme example of a super zoom camera is the Nikon P900 from 2015, which is nominally equipped with an 83x zoom range. As of 2014, around half of compact cameras have been equipped with up to ten times zoom and the other half with over ten times zoom. Some compact cameras, often high quality, still have three times the zoom range.

#### Integration with other devices

Digital cameras have been increasingly integrated with other devices since the 2000s:

• Almost all modern cell phones and smartphones contain a built-in digital camera. There are now smartphones that are equipped with up to 108 megapixels (Xiaomi Mi (Note) 10 (Pro), Samsung Galaxy S20 Ultra).
• Video camcorders have photo capabilities because they work similarly to digital cameras. In 2003, Samsung launched the first hybrid device, the VP-D5000i.
• The integration of digital image previews in film-based compact cameras with the Advanced Photo System (APS) has not caught on.
• Personal digital assistants , now hardly in use, had integrated simple digital cameras.

On the other hand, many digital cameras have the option of recording films even in high resolutions ( HDTV , Ultra HD ) with sound or outputting the digital signals directly to an appropriate interface without intermediate storage. This means that they can also be used as a webcam or camcorder, if necessary . The operating system of digital cameras is now also influenced by smartphones . This is how Android- based digital cameras already work .

#### Reproduction of the pictures

Although many photographers still want to see their pictures as paper prints today, the proportion of prints made by photo laboratories has fallen sharply. There were essentially five reasons for this:

1. At this point in time, the photo labs were in a price war, in which production was sometimes also below the production price. Therefore, since that time there have only been two large laboratories (the remaining providers have only insignificant market shares), which supply almost all photo acceptance points (centers, drugstores, gas stations, etc.).
2. The hybrid technology APS (a film with an electronic storage layer) was introduced as a global standard, but due to disputes between the global market leaders with a delay of four years. A substantial part of the investment volume was thus tied up in the photo laboratories (which were involved in this market launch).
3. In the early years of digital photography, it was either very expensive or of poor quality. In the photo labs, the future volume of orders for digital work was wrongly estimated and only insignificant sums were invested in the following years.
4. The manufacturers of inkjet printers offer good “photo printing at home” with greatly reduced costs.
5. Worldwide there is photo production in large laboratories only in core Europe. Photo booths that produce the prints on site have the largest share worldwide. In Germany, too, their share has risen steadily in recent years.

## functionality

The main components of a digital camera: storage medium and battery can usually be changed. With system cameras , the lens and the flash can also be changed . The other components, the monitor , shutter release and image sensor, are usually built into the camera housing .

The photographic image is created in a digital camera in the following steps:

1. Optical projection through the lens onto the image sensor
2. Optical filtering, for example through high and low pass , infrared , color filters and color mosaics (mostly integrated in the image sensor)
3. Conversion of light intensities into analog electrical quantities; then discretization / digitization of the values ​​through analog-digital conversion ( quantization )
4. Determining the settings:
1. Focusing of the image either with autofocus or manually, whereby aids such as a focusing screen (with optical viewfinder) or software magnifying glass and edge enhancement (with digital viewfinder image) are possible
2. Estimation of a reasonable exposure time and f-number ( exposure value )
3. Set the device to these values.
5. Resetting the converter chip, renewed image acquisition (steps 1..3), now with the focus, exposure time and aperture just set.
6. Image processing of the image file:
1. Color reconstruction / merging of sub-pixels into full-color pixels b
2. Noise reduction b
3. Removal of known, correctable errors in the image recording system ( defective pixels , crosstalk , re-sharpening , edge light drop , distortion , chromatic aberration ) b
7. Compression of the image file c
8. Storage of the image file in the desired format; possibly other output.

Remarks:

bNot applicable when saving in raw data format .
c Depending on the desired output format.

With a digital camera, light enters the camera housing through lenses (lens) that project the image onto the sensor. In front of the sensor, the light usually passes through an infrared, a low-pass filter and a color filter. In combination, microlenses are usually built in, which focus the light on the sensitive areas of the image converter behind.

The image sensor performs an image conversion that consists of the steps of discretization and quantization . The discretization means the image decomposition into discrete, that is non-continuous, units (here: local discretization: Space allocation in the (sub-) pixels; temporal discretization "zeros" of all the pixels, exposing accordance with the predetermined exposure time). During quantization , the signal strength of each subpixel is converted into a natural number by an A / D converter . Since cameras that use the RGB color space need to store three color values per full-color pixel , at least three single-color (R, G and B) sensor elements are "weighted" combined for each pixel ( demosaicing ; see also Bayer -Sensor ).

After the optional compensation of imaging errors , compression is carried out to reduce the data volume if the image is saved using the JPEG method, as is generally the case. The extent to which raw data (raw format) is also compressed depends on the proprietary format of the respective manufacturer.

### Image transformation

CCD sensor on flexible circuit board

As with an analog camera, the incident light is collected with a lens and focused on the film plane, in this case the sensor . The film plane is usually a much smaller area than an image on the analog 35 mm film of a 35 mm camera ; only higher quality digital cameras have image surfaces (and thus sensors) the size of the APS- C negative or even a full-format sensor . Larger sensors are also used in the professional medium format sector.

The sensor can either be an area sensor or (rarely) a line sensor . The area sensor is fixed in the plane of the film, it simultaneously registers the entire image. Line sensors are used in scanner cameras that work according to the scanner principle , that is, they work similarly to a flatbed scanner and scan the image line by line: The line sensor is driven over the film plane by means of a drive, and line by line is recorded.

The three basic colors can be recorded simultaneously in the same sensor , which then has three sub-pixels for each full-color pixel. However, the primary colors can also be recorded spatially separately by z. B. a system of semi-transparent mirrors distributes the incident light to three separate sensors for the three primary colors. As a third option, the primary colors can be recorded separately in time: Simultaneously ( one-shot cameras ) or one after the other ( three-shot cameras ), whereby a different color filter is then connected before each recording.

The majority of all cameras use an area sensor with subpixels.

There are essentially two different types of surface sensors available on the market, the widely used CCD sensor (for example in cameras from Canon , Hewlett-Packard , Kodak , Nikon , Olympus , Panasonic , Pentax , Samsung or Sony ) with the variant of the super CCD Sensor (only Fujifilm ) as well as the CMOS sensor .

The Foveon sensor, which is used in Sigma cameras, has a special position . This is a three-layer sensor that records red, green and blue light with every pixel. Therefore, the three photo detectors determine the exact pixel color. This multilayer principle corresponds to the application of color films in color photography , in which different color-sensitive layers are also superimposed. The Foveon X3 sensor has been revised for the Sigma dp2 Quattro and can achieve a higher resolution compared to the previous models. Despite the interesting principle, the second generation equipped with microlenses did not lead to resounding success either.

### Image processing

In a digital camera, the electronics (partly controlled by the firmware ) carry out a series of image-changing processes before, during and after the recording; these are summarized under the term image processing . This is to be distinguished from the image processing that is carried out on the finished recording.

The digital camera tries to capture the colors perceived  by a person in daylight or artificial light by means of the white balance - like the video camera - while losing the absolute color fidelity.

The homogeneity, i.e. the uniform sharpness and brightness over the entire image, especially at the edge of the image, depends on the imaging properties and can be partially compensated for by the software in the camera.

The quality of the camera's internal electronics also determines the signal dynamics , that is, the brightness levels distinguishable by the camera and the contrast range of the digital image.

The camera electronics also influence the image purity or the degree of image errors, which can be seen, for example, as image noise or compression artifacts .

• Digital fingerprint
CCD errors can hardly be avoided in cameras with a resolution of three megapixels and more: Individual cells may not work at all, others, on the other hand, work with different sensitivities, etc. Such "dropouts", as well as the image noise that occurs especially during night shots, can come from the camera Electronics are at least reduced.
Nevertheless, there remains an individual pattern for each individual camera, which can be extracted as a digital “ fingerprint ” if at least two images are present . Every image sensor in every digital camera - from cell phones to professional devices - has a unique fingerprint that it leaves in every image. So you can assign an image to a camera, just as you can assign a bullet to a weapon. Instead of the scratches on the cartridge case, the noise-like pattern in the image is examined. This procedure is considered legally valid. The analysis method was developed primarily for photos and videos, it is even possible to extract the fingerprint from printed images. Even in the event that someone inserts a fake fingerprint into a picture, there are now methods of discovering this.

The firmware also performs various optimizations to improve the subjective image effect . These include, for example:

• Sharpening: Recognize and reinforce transitions / edges in the image;
• Contrast increase : increase the contrast in the image;
• Color saturation: Increase the color saturation.

Before a photo is taken, the autofocus may be activated, which takes over the focusing. Even if several photos are taken of the same object, they must be focused. The autofocus can be switched off with some cameras. Except for the lenses of digital system cameras, you will look in vain for a focus setting ring on most digital cameras. Manual focusing in stages can only be achieved via a menu structure, which limits the possible uses of most digital cameras. Even if the autofocus is switched off, a white balance takes place in the camera electronics before the shutter is released. However, because this is not sufficient, a black balance is also carried out in order to filter out the electronic noise of the sensor and faulty pixels.

## Optical system

KB-equivalent focal length specification on a digital camera lens

Almost all digital compact cameras and also many digital system cameras use an image sensor with a sometimes considerably smaller area than cameras that work with films in the widespread and, for many, familiar 35mm format . The smaller image area of ​​the sensor results in a smaller image angle with the same focal length of the lens , or in other words, in order to obtain the same image angle, the focal length must be correspondingly smaller. The relationship is given by the formula for distortion-free lenses

${\ displaystyle f \ cdot \ tan \ alpha = h}$

described. This includes the focal length, half the diagonal angle of view (measured from the optical axis) and the image height (distance between the corner of the sensor and its center). In the 35mm format, the normal focal length is 50 millimeters and the image diagonal is 43.3 millimeters, resulting in a normal angle of view of 46.8 °. The ratio of image diagonal to normal focal length is constant, whereby the image diagonal is always 15.6% shorter than the normal focal length: ${\ displaystyle f}$${\ displaystyle \ alpha}$${\ displaystyle h}$${\ displaystyle q}$${\ displaystyle d}$${\ displaystyle f_ {N}}$

${\ displaystyle q = {\ frac {d} {f_ {N}}} = {\ frac {2 \ cdot h} {f_ {N}}} = {\ frac {2 \ cdot f_ {N} \ cdot \ tan \ alpha} {f_ {N}}} = 2 \ cdot \ tan \ alpha = 2 \ cdot \ tan (46 {,} 8 ^ {\ circ}) = 0 {,} 865 = {\ frac {1} {1 {,} 156}}}$

The fact that the image angle is smaller compared to the 35mm format with the same focal length is often incorrectly referred to as a focal length extension . Photographers are used to seeing the focal length as a measure of the angle of view (the larger the focal length, the smaller the angle of view), but that only works as long as the image format does not change. To ensure that this assignment continues to work as it is used to from the 35mm format, many manufacturers of compact digital cameras also specify the focal length in addition to the real focal length of their lenses, which would result in the same angle of view in the 35mm format (KB-equivalent focal length).

For digital system cameras with interchangeable lenses , a conversion factor is usually specified - the format factor - by which the focal length of a lens must be multiplied in order to calculate the focal length that takes the same angle of view on a small picture. For system cameras with full-format sensors 36 mm × 24 mm, the format factor is therefore 1.0. Cameras with smaller image recorders with a ratio of 1: 1.3, 1: 1.5, 1: 1.6 or, as with the Four Thirds system, approx. 1: 2 to the traditional 35mm format are widespread . The format factor is the reciprocal of it. With compact cameras and most bridge cameras , the ratio is significantly smaller.

### Digital zoom

In addition to the optical zoom built into most digital compact cameras , many models also have a so-called digital zoom. In fact, this is an enlarged section in which only a part of the center of the sensor surface is used with a correspondingly reduced image resolution. This section is enlarged in the camera to the resolution set in each case . Digital zooms can be useful for photographers who do not want or cannot post-process their images. They are not a substitute for an optical zoom lens that would offer the same magnification, since the interpolation usually only achieves very unsatisfactory results depending on the zoom level. Subsequent digital enlargement with suitable image processing software is generally at least of the same quality and at the same time more flexible, since, for example, the image section can still be shifted.

## Viewfinder systems

Digital cameras have different viewfinder systems that allow the image to be designed before it is recorded. A basic distinction is made between optical and electronic viewfinders.

Optical viewfinder :

As with conventional film-based cameras, the optical viewfinders work either with a reflex system or as a separate see-through viewfinder, although only a few digital viewfinder cameras offer a high-quality rangefinder .

Electronic viewfinder :

The vast majority of digital compact cameras as well as camera phones only have an electronic viewfinder with a display (no viewfinder).

Electronic viewfinders either use the signal from the camera sensor directly or, as is sometimes the case with some SLR designs, an additional built-in sensor. The display is on a mounted on the back of the camera display , in addition, a second micro-monitor can be integrated in the housing, which is combined with a conventional eyepiece.

Electronic viewfinders largely show the exact image section that would be saved when the camera was triggered. A precise assessment of the image sharpness and especially the sharpness curve is not easy because of the small format and the mostly relatively low resolution of the monitors. Help, such as a digital viewfinder magnifier , can help . In addition, sometimes extensive status information or, for example, grid lines for precise camera alignment can be displayed.

The construction of electronic viewfinders requires that the recording sensor, with the exception of some special constructions, must be permanently active. This leads to a comparatively high power consumption and to the heating of the camera and the recording sensor, which can have an adverse effect on the image noise . This also applies to most devices with a SLR design if the live view function is used. Single-lens reflex cameras that are operated conventionally do not show this effect or only show this with long exposures , since the recording sensor is only active during the actual recording.

## Types of a digital camera

The compact camera and single-lens reflex camera designs known from film-based photography are also represented in digital photography, although there are also a number of other forms.

### compact cameras

Compact digital camera with retracted and extended zoom lens

While SLR cameras differ little in appearance and structure from their film-based predecessors, what is particularly noticeable about compact cameras is the extreme miniaturization made possible by the significant reduction in the recording format ( format factor around 6 compared to 35mm format). The optical viewfinder, which is now rarely installed, has been replaced by large-format displays for creating images.

The housing formats for ultra-compact cuboid formats with the dimensions of a cigarette packet have become established, whereby the lens disappears completely in the front when idle and is automatically closed. Some compact cameras are built with an internal lens: the front lens is rigid in the housing, the light is directed by means of a prism onto the movable lens elements for zoom and focus inside the housing, which are arranged perpendicular to the recording direction. This design, known as the “periscope lens”, enables particularly robust cameras that can even be used under water.

For more ambitious models, a design similar to that of classic compact cameras with a protruding lens and grip bead is common. New types of special designs, for example with rotatable housing halves such as the Pentax Optio  X, have not caught on.

### Bridge cameras

One of the first hybrid forms between compact and SLR cameras established on the market was the so-called bridge camera with a fixed lens and electronic viewfinder, similar to the optical viewfinder of a SLR camera. Bridge cameras usually have super zoom lenses.

### Mirrorless system cameras

Based on the Micro Four Thirds standard introduced by the manufacturers Olympus and Panasonic at the beginning of 2008, the LUMIX DMC-G1 was the first camera with an interchangeable bayonet , but without an oscillating mirror, which at the same time established a new class of digital system cameras , the so-called MILC , EVIL- or CSC cameras (for mirrorless interchangeable lens , electronic viewfinder interchangeable lens or compact camera system as, in German mirrorless camera with interchangeable lens , camera with electronic viewfinder and interchangeable lens or compact system camera ).

In early 2010 and presented Samsung with the NX10 before a mirror-less system, as with Sony cameras the Sony NEX series, a sensor in the APS-C used format. In the summer of 2011 finally brought Pentax with his Pentax Q a likewise mirrorless system camera on the market, which, like the Nikon 1 series (autumn 2011) is based on a much smaller image sensor. At the beginning of 2012 Pentax brought the K-01 and Fujifilm the X-Pro1 on the market; both use an APS-C format sensor.

### SLT cameras

SLT cameras (for single lens translucent (mirror) ) are another variant of digital cameras from Sony , which stand between mirrorless system cameras and conventional digital single lens reflex cameras with oscillating mirrors (DSLR). They use a partially transparent mirror as a beam splitter for deflecting or dividing the incident image onto the photo sensor and the autofocus detector. The design and sensor size are similar to those of DSLR cameras, which means that interchangeable SLR lenses with a suitable lens connection can be used. The mirror is used here solely for the auto focus by means of phase comparison . In contrast to SLR cameras, the viewfinder image is generated electronically, which - as with compact and mirrorless system cameras - enables a preview of the expected image. SLT cameras have the advantage of fast autofocus (even when filming), the real preview of the image and - since the mirror does not have to be folded up - a much higher series image speed, a smaller delay when the shutter is released and the shutter noise is quieter. The disadvantage is a small time delay in the viewfinder image and a loss of light of 20 to 30%.

### Digital SLR cameras

Many manufacturers also offer system cameras with a reflex system , in which the film of the conventional "analog" camera is replaced by a digital image sensor. They are referred to in English as digital single lens reflex , or DSLR for short. Accordingly, there is a large selection of interchangeable lenses for such cameras, but mostly with a much lower zoom factor than the fixed zoom lenses of compact and bridge cameras. Similar to conventional system cameras, there are also versions with an exchangeable, in this case digital camera back that is attached to the camera body, as well as models where you can switch between analog or digital back.

## Sensor pixels, photo resolution and image quality

### Effective resolution in the interaction of optics and sensors

The effective resolution is given in line pairs per millimeter; It is said that a lens can map a certain number of line pairs per millimeter (lp / mm) on a certain sensor. Conclusions about the effective resolution in megapixels can be derived from the determined line pairs. Depending on the optical imaging performance in combination with the aperture , different values ​​usually arise for the center and edge of the image.

The light falls through the camera lens (optics) onto the sensor. This is where the physical limits of the optics (aperture) interact with the area of ​​the sensor pixels (pixel size).

With modern high-resolution image sensors of well over 16 megapixels, a small number of pixels no longer represents the bottleneck with regard to the associated assessment of the overall quality of a camera. A higher resolution does not necessarily lead to a higher impression of sharpness . A compact camera with a 1 / 2.3 ″ sensor, for example, has a sensor size of 6.2 mm × 4.6 mm, which at 16 megapixels leads to a pixel size with a side length of 1.35 µm (in height and width) . Due to the diffraction on the lens with a typical aperture of F2.8, a point of light is mapped onto a diffraction disk with a diameter of 3.75 µm. This means that with these sensor sizes it is not possible for a point of light to illuminate only a single pixel, even if one assumes a lens without imaging errors , whereby cheap cameras are often saved.

The optical resolution depends on the size of the diffraction disk and thus on the aperture of the lens .

With a medium format sensor measuring 48 mm in width and 36 mm in height, a pixel size of 3.75 µm matching the aperture F2.8 can be achieved with a resolution of 123 megapixels. Common full-format sensors (also known as 35mm format), which are 36 mm wide and 24 mm high, have 61 megapixels. With an even higher resolution, even with these relatively large sensors, the physically sensible limit for lenses with an aperture of F2.8 (or higher) is exceeded.

For comparison, high-resolution slide films in analog photography offer an even finer granularity, such as the Fuji Velvia 50 . Fuji states the performance of this film under ideal contrast conditions with 160 lines (80 line pairs) per millimeter; a digital camera would need a 35-mm full-format sensor with 87 megapixels to achieve this resolution. This information is based on a common Bayer color sensor , which detects the colors red, green and blue with separate sensor pixels in order to then add them together to form a color value. In contrast, with a monochrome sensor 44 megapixels are sufficient to be able to record 80 lp / mm. Provided that the lens aperture is suitable for the respective resolution:

With a very bright lens with an aperture of F1.5, the diameter of the light point (the diffraction disk) is only 2 µm, which corresponds to an optical resolution of 125 lp / mm as soon as the light points hit a color sensor, or 177 lp / mm when using a monochrome sensor. With aperture F2.2, each point of light takes up 3 µm (83 lp / mm color or 118 lp / mm monochrome). Under ideal conditions (without optical aberrations, no blurring, as well as good light and ideal contrast), such lenses could even deliver a higher optical resolution than the Fuji Velvia 50 with its 80 lp / mm or an 87 megapixel 35mm full-format color sensor can capture . With aperture F3, however, the diameter per light point is 4 µm (62 lp / mm color or 89 lp / mm monochrome), with aperture F4.5 it is 6 µm (42 lp / mm color or 59 lp / mm monochrome) and Aperture F6 is 8 µm (31 lp / mm color or 44 lp / mm monochrome).

Comparison of common sensor formats
 Typical designation of the sensor size (b) Aspect ratio Width (mm) Height (mm) Diagonal (mm) Area (mm²) Area (%) based on KB Maximum optical resolution in megapixels at aperture F2.8 (F2.8 generates a point of light that corresponds to a pixel size of 3.75 µm, (j) from which the sensor resolution of this column results; (d) even with more megapixels a digital camera at F2 , 8 optically (k) no higher resolution (h) ) Resolution at F1.5 (2 µm (l) ) Medium format (s) 4: 3 048.0 036.0 060 1,728 200 123 433 35mm, full format (KB), FX 3: 2 036.0 024.0 043.3 0864 100 061 216 DX , APS-C (f) 3: 2 023.7 015.6 028.4 0370 042.8 026th 092 4 ⁄ 3 ″, four-thirds , micro-four-thirds 4: 3 017.3 013.0 021.3 0225 026th 016 056 1 ″, CX format (high-end compact cameras and compact system cameras) 3: 2 013.2 008.8 016 0116 013.5 008th 029 (g) 1 ⁄ 1.7 ″ (high-end smartphones ) 4: 3 007.6 005.7 009.5 0043 005 003 011 (g) 1 ⁄ 2.3 ″ (low-end compact cameras and some smartphones) 4: 3 006.2 004.6 007.7 0029 003.3 002 007th
(a) Assuming an objective without aberrations with a typical largest aperture of F2.8, which images a point of light onto a diffraction disk of 3.75 µm diameter or 2 µm diameter for aperture F1.5.
(b)The size specifications in fractions of an inch traditionally refer to the size of video pickup tubes. A one-inch vidicon picture tube has an outer diameter of 25.4 mm, but only a usable screen diagonal of around 16 mm.
(c)Formula for color sensors in line pairs per millimeter: 500 / (pixel size in µm * 2); Formula for monochrome sensors : 500 / (pixel size in µm * 1.41) according to OptoWiki , accessed on May 14, 2019.
(d)According to sensor calculations on vision-doctor.com to calculate the pixel size in µm (with decimal places ) and pixel size calculator on lcdtech.info as a second reference (without decimal places, but with MP calculation), accessed on April 22, 2019.
(e)Medium format sensors can have different sizes depending on the manufacturer and model. The dimensions listed in the table fit e.g. B. to Mamiya ZD
(f) APS-C sensors can have different sizes depending on the manufacturer and model.
(G)In high-end cameras such as the Sony RX100 (variant I to V), the lens works with an open aperture of F1.8. High-end smartphones from 2019 sometimes have camera lenses that work with an aperture of F1.4 (Xiaomi Mi 9 Explorer Edition) or 1 / 1.6 (Huawei P30 Pro). The diffraction disk has a diameter of about 2 µm.
(H)The sensor resolution specified in this column is required in order to be able to capture all light points of the lens. In addition, it is no longer possible to optically detect line pairs per millimeter even if the image sensor has smaller pixels and thus a higher resolution. Because the optical resolution is limited by the size of the diffraction disk, which depends on the aperture. The sensor has no influence on the optics. Nevertheless, a higher sensor resolution can be helpful in improving the image quality, because the technical limits are not exhausted in digital photography . The effective resolution can therefore be significantly higher than the optical resolution, depending on the computing power of the camera.
(i)A common Bayer color sensor detects fewer line pairs per millimeter than a monochrome sensor , because each color value has to be calculated from different pixels.
(j)Formula: D = 2.44 * 550nm * F corresponds to 1.342µm * F (where F is the f-number and D is the diameter of the diffraction disk, calculated at a typical wavelength in the green of 550 nanometers), according to image recording , digital imaging methods, wikibooks - the free library, chapter "Critical aperture", section "Calculation on a plano-convex lens", accessed on December 27, 2019
(k)This corresponds to 67 line pairs per millimeter (c) (lp / mm) on a color sensor or (i) 95 lp / mm on a monochrome sensor .
(l)F1,5 generates a point of light (j) which corresponds to a pixel size of 2 µm, from which the sensor resolution of this column results; (d) Even with more megapixels, a digital camera cannot optically resolve at F1.5 higher. (h) This corresponds optically to 125 line pairs per millimeter (c) (lp / mm) on a color sensor or (i) 177 lp / mm on a monochrome sensor .

The resolution values ​​in the table relate solely to the physical limits of optics; A lens without aberrations is required. In contrast to analog photography, digital photography does not exhaust the technical limits. The phenomenon of diffraction has been scientifically and mathematically worked out so that it can be calculated. Provided there is sufficient computing power, it is possible to calculate the effects of diffraction from an image in the camera. In addition, a tricky generation of an image, which is created, for example, by adding together several images, can help to significantly improve the image quality. It would be conceivable to add two recordings together with the aperture open and with the aperture set in the camera in order to increase the resolution at the focus level. The possibilities of digital image processing deliver remarkable results. For example, in November 2019 it was possible to determine an effective resolution of 90 line pairs based on an image from a 61-megapixel 35mm camera that was taken at aperture F8. The side effects of high resolution such as increased noise, artifacts and loss of texture can also be calculated with sufficient computing power. The higher the number of pixels in the sensor, the better the conditions for it .

On a lens without aberrations, a higher f-number reduces the optical resolution on the entire imaging surface in purely mathematical terms. In contrast, it counteracts optical aberrations. The larger the image circle of the lens, the more difficult and expensive it is to minimize lens errors. Compared to an open aperture, a higher f-number therefore often increases the resolution at the edge of the image up to a certain point. On the other hand, it usually decreases faster in the center of the image with increasing f-number than at the edge, because this is usually the area with the lower aberrations. However, aberrations in the center of the image can lead to the phenomenon that the highest resolution is not achieved with an open aperture; Both on the 50 megapixel Canon EOS 5DS R with the Canon EF 35 mm F1.4 L II USM lens and on the 61 megapixel Sony Alpha 7R IV with the Sony FE 35 mm F1.8 lens , the best resolution value in the The center of the image is only reached at aperture F4, with a clear drop at higher and lower apertures.

The effective resolution that results from the interaction of optics and sensors can be determined using test images, for example with the resolution chart according to ISO 12233.

The interaction between optics and sensors can be determined, for example, using a Siemens star. The two pictures on the left show the resolving power towards the center of the picture using a test photo with a detail enlargement. In the middle of the Siemens star, there is a blurred spot called the gray ring . The effective resolution of a test system can be calculated from the size of the gray ring. In the example illustration, test system 1 creates a larger gray ring and is therefore lower in effective resolution than test system 2.

### Medium format and 35 mm full format

The largest sensors in digital photography are the medium format sensors. There are different sensor sizes for the medium format; Even within the products of a manufacturer, their dimensions vary ( e.g. Pentax 645Z: 43.8 × 32.8 mm, Pentax 645D: 44.0 × 33.0 mm, Hasselblad H5D-40: 43.8 × 32.9 mm, Hasselblad H5D-50: 49.1 × 36.7 mm, Hasselblad H5D-50: 53.7 × 40.2 mm, Hasselblad H5X: 56.0 × 41.5 mm, Mamiya ZD: 48 × 36 mm).

The next smallest sensors are the full format sensors (also called 35mm format). Their width and height are uniformly 36 * 24 mm.

Even if theoretically a lens with the typical largest aperture of F2.8 could optically resolve on a 35mm full-format sensor with a maximum of 61 megapixels , in practice 40 megapixels are already marginal, since even the best lenses available on the market in 2015 are not sufficient Provide details for this resolution: Numerous lenses from the professional segment can usually provide such sensors with a resolution of around 20 megapixels, rarely 30 megapixels with enough detail; only the Zeiss Otus 85 managed a resolution of 35 megapixels in 2015. The demands on the photographer increase with the resolution. A high-resolution image sensor of significantly more than 20 megapixels in good lighting conditions in combination with extremely good optics only brings an increase in detail if the photographer pays attention to exact focus accuracy and has a very steady hand, as even small blurring counteract the increase in detail. If the sensor resolution is significantly higher than the resolution of the lens, reducing the photo resolution can help to improve the image quality.

Noise is less noticeable on the reduced image. Clicking on it shows it on a single pixel level. The square cutout is noise filtered.
A: low image noise at ISO 100
B: high image noise at ISO 3,200

Since the pixel size and - depending on it - the pixel pitch (pixel pitch) becomes smaller with increasing sensor resolution, they become more susceptible to image noise in unfavorable lighting conditions , which leads to a loss of detail and brilliance. In order to keep this effect low, 35 mm full-format sensors should ideally have a resolution of not significantly more than 20 megapixels. In contrast, a 50-megapixel camera with the same sensor size has more noise than a 20-megapixel camera when viewing the raw data at the individual pixel level (raw format). However, if you look at the two photos on the same size output (for example on an A4 printout), the image impression is the same; more megapixels do not necessarily lead to higher noise in the printout. In addition, the higher the resolution, the better the image noise can be automatically eliminated in the camera (noise filter), since more neighboring pixels can be used for calculating an average for each area section if there are strong deviations in individual values ​​(noise). The noise increases in the raw data, but decreases again in the end product (the finished JPEG). If the raw data is processed on the computer, this mechanism ( denoise ) within the processing software (raw converter) usually comes into play there as well .

The textures of fine details can visibly suffer from such noise reduction. See the square section in the picture on the right in the area of ​​the leaves. This counteracts the (possible) gain in detail of the high resolution. Nevertheless, a comparison between, for example, the Sony A7 II (24 megapixel camera) and A7 R II (42 megapixel camera) shows a considerable advantage of the high-resolution image sensors, especially in this discipline: In a test laboratory, the raw data was initially examined at the individual pixel level . The 24 megapixel camera was clearly superior to the 42 megapixel camera in terms of signal-to-noise behavior. Nevertheless, the photo of the 42 megapixel camera, reduced to the same output size, provides more details in the final JPEG product, despite stronger noise suppression - quote: "Here the high-resolution 35mm image sensors can actually benefit from their higher resolution despite smaller [noise-sensitive] pixels at high ISO" . Up to ISO 12,800, the A7 R II delivers a more than usable image quality with only a slight loss of detail, while the A7 II with 24 megapixel image sensor, on the other hand, has a limit of ISO 3,200.

The ISO value determines how much energy the sensor is controlled with. It influences the light sensitivity of the sensor and can be between ISO 50 or ISO 100 (suitable for bright daylight or for long exposure times) and a few hundred, thousand, ten thousand, sometimes even a hundred thousand. The higher the value, the shorter the exposure time can be, which is particularly useful for taking blur-free photos in low light without a tripod. However, this increases the image noise.

As of February 2018, in a high-ISO resolution comparison with ISO 51,200, the higher-resolution camera also provided the better images. The raw files of a Sony Alpha 7S II (12 megapixels) were compared with a Sony Alpha 9 (24 megapixels) and Sony Alpha 7R III (42 megapixels). The higher-resolution camera shows a more aggressive noise, but contains significantly more details and the noise is finer-grained and therefore less annoying, whereby the image appears significantly sharper overall. Within this test, it was irrelevant for the result whether the image from the high-resolution cameras was scaled down or that from the low-resolution cameras upscaled for the comparison.

### APS-C format, compact cameras and cell phones

The effect of a high sensor resolution when using small compact camera and cell phone sensors is very different from cameras that are equipped with a 35mm full-format sensor.

As of February 2015, even the relatively large sensors of APS-C cameras with a good lens only have an optical resolution of around 9 megapixels, even if the sensor promises 20 megapixels or more and theoretically an optical resolution of 26 megapixels would be possible (on a Lens with a typical aperture of F2.8). The 4⁄3-inch sensors of the Four Thirds and Micro Four Thirds cameras can in theory have an optical resolution of up to 16 megapixels on such a lens, in practice they only come to around 5 megapixels in 2015. In contrast, laboratory tests as of February 2018 show that although micro four thirds cameras are usually equipped with 20 megapixel sensors, the cameras hardly achieve more resolution than 16 megapixels. Conversely, this means that an increase in resolution of up to 16 megapixels was possible.

Other compact camera sensors are usually much smaller. The smallest representatives can usually be found in cell phones. The smaller a high-resolution sensor surface, the greater the effect of the image noise. Its adjustment has a strong influence on the display of the details, which is no longer only noticeable when looking at the individual pixel level, but also when looking at the entire photo. Here it can help to reduce the photo resolution using the camera setting .

### Decrease photo resolution to increase image quality and performance

High-resolution photos are greatly reduced in resolution during processing (printing, etc.), which at first glance speaks against a high sensor resolution. On the other hand, the following principle applies: Even under ideal conditions (large image sensor, good optics), a scaled down (reduced) photo from a higher-resolution camera is more detailed than that of a camera with precisely this resolution. This also applies in poor lighting conditions. Because although the pixels are smaller and therefore more sensitive to noise, the higher the resolution of an image sensor, a reduced photo can contain more details despite greater noise reduction at high ISO values .

There is no loss of detail with the reduction, as long as either the resolution of the lens is not undershot . This is the lower reduction threshold, which for full-frame sensors, for example, can be 30 megapixels depending on the lens, which still produces large photos and thus ensures freedom of editing. Or the required size for the output is selected as the resolution setting (for example 8 megapixels for DIN A4 printouts in 300 dpi or for output on a 4k monitor, etc.). This is the upper reduction threshold that should not be exceeded in order to avoid loss of quality in the output. It is mainly suitable for photographers who do not edit their photos afterwards. The ideal camera setting is therefore dependent on the requirements of the photographer and could usefully lie between these two thresholds.

12 megapixels, for example, offer scope to straighten the horizon with additional space for minor cropping work, which further reduces the resolution without falling below 8 megapixels as a result. 20 megapixels allow larger cutting work. If the result is smaller, for example 6 megapixels, the A4 printout can still be made with 255 dpi, which leads to a slight loss of detail. In practice, the difference is hardly noticeable; Stiftung Warentest even writes that 4 megapixels are sufficient as a basis for photo prints and section enlargements, which according to the dpi table is applicable up to a printout of 13 × 18 cm.

Due to the interaction of optics and sensors and their limits in high-resolution compact cameras and cell phones , Stiftung Warentest recommends reducing the photo resolution to a quarter of the sensor resolution in order to improve the image quality, whereby the output format does not go below 4 megapixels. A quarter of the sensor resolution is also a good choice because, depending on the camera, four pixels can then be merged into one pixel during recording, which results in better recording quality, especially with small camera sensors. In part, this is due to oversampling (English: oversampling ) is reached.

Regardless of the sensor size, excessively high-resolution photos make the image files unnecessarily large, the dark current behavior is negatively influenced and the data transfer , the copying of photos and the image processing are slowed down. So it can make sense to reduce the resolution of the photos already in the camera. This also has a positive effect on the image quality, on the one hand because the reduction in size already reduces the image noise, on the other hand because this intervention ensures that the camera processes the image less aggressively when removing the noise. In contrast to the noise reduction inside the camera , the reduction also has a correspondingly positive effect on the raw data. Such a small raw mode is called, for example, by Canon “mRaw” and “sRaw” (each with different reduction levels). In contrast, many camera models do not have a corresponding setting that allows the raw format resolution to be reduced in addition to the files in JPEG format; at Canon, these modes have so far been reserved for the more expensive cameras (as of 2018).

### Limits of visual perception

Contrast Sensitivity Function (CSF) versus spatial frequency in pairs of lines per image height

The maximum contrast perception of the human eye is at a spatial frequency of about five arc minutes . In good lighting conditions, the healthy eye has a resolution of around one arc minute at which differences in brightness can still be detected. With a normal viewing angle of around 47 ° for the image diagonal , there is a number of around four million image points (around 1500 line pairs along the diagonal), which can be differentiated without color information. For a picture with maximum contrast perception, only 0.2 megapixels are sufficient for a normal picture angle (around 300 pairs of lines along the diagonal). If the angle of view is larger than the normal viewing angle, the image can no longer be fully captured at a glance and only a section is viewed. If the angle of view is smaller than the normal viewing angle, even fewer pixels are sufficient without restricting the perceived resolution or perceived contrast.

It should be noted that most image sensors used in cameras are Bayer sensors that only register a single primary color in each image point (“ subpixel ”) . In these cases, the missing colors are determined by interpolating the neighboring pixels. The “effective resolution” is therefore somewhat lower than the subpixel density. Although this is disadvantageous, other significant influences on the impression of sharpness remain almost completely intact.

As explained above , infrared radiation is normally filtered out before the light hits the sensor, as the sensor is sensitive to wavelengths of just over 1 μm (visible light only has wavelengths up to approx. 0.7 μm) due to its basic material silicon . However, this filtering is not carried out too rigidly, so that a significant proportion of such “near infrared radiation” still comes through. You can easily check this by pointing a remote control for a TV or DVD player or similar at the camera. In the digital viewfinder you can clearly see a (whitish) light, while the eye cannot see anything. But it's only about near infrared; the effects that are achieved in infrared photography with special infrared films, such as the disappearance of annoying haze in long-distance shots, only come into play at significantly higher wavelengths that cannot be achieved with these sensors.

## speed

Digital compact camera with hybrid autofocus

The operating speed of a digital camera is mainly determined by four characteristic features:

1. Readiness for exposure , the amount of time that the digital camera needs after being switched on to be able to take a photograph.
2. Focus speed , the amount of time it takes for the autofocus to focus.
3. Shutter lag , the amount of time that elapses between pressing the shutter button and actually taking a picture.
4. Image sequence time , the length of time after a recording after which the camera can take a subsequent image. The maximum frame rate of the digital camera is directly related to this .

Despite rapid technical development, many digital compact cameras are significantly slower than their 35mm counterparts . The image sequence times in particular often drop massively after a few shots, while motorized 35mm cameras achieve the same speed over the entire film.

With high-quality digital cameras, on the other hand, the shutter release delay and frame rate are comparable to their analog counterparts.

## power supply

Some analog cameras can be used without any electrical energy - digital cameras, however, always require electrical energy. This must be taken into account when switching to digital photography. In addition to the large power guzzlers and flashes built into analog cameras, the sensors, electronics and LC displays also consume significant amounts of energy in digital cameras. Every digital camera therefore requires a continuous energy supply, which is usually guaranteed by a battery or a power supply unit; There are also some special constructions based on solar energy , for example .

The energy content of the battery determines - in connection with the power consumption of the camera electronics and its power saving functions - the maximum operating time of the camera until a battery change is necessary. Proprietary battery types (mostly lithium-ion batteries ) are significantly more expensive than standard batteries ( AA or AAA etc.), but often also more powerful, that is, they have a higher energy content with the same size or weight and therefore have a longer service life. An average battery with an energy content of 6 Wh supplies a digital camera with energy to take around 200 pictures.

## File format

In order for an image with a resolution of ten megapixels and three color channels per pixel not to require thirty megabytes (uncompressed file size) on the memory card, it is usually compressed .

The Exif standard JFIF (“JPEG”) is usually available as a lossy format, while TIFF was also offered as a lossless format . With many cameras, the digital images can also be saved loss-free in a proprietary raw data format (English raw for "raw").

Since there is no established standard for the raw data format (see also digital negatives ), the image data from different camera manufacturers and even different series from one manufacturer are usually not compatible with each other and must be viewed or processed using a program or a so-called plug-in, often provided by the camera manufacturer can be converted into a standard image format (usually TIFF or JPEG) for image editing programs .

Raw data is also known as a digital negative . Due to their generally lossless storage, raw data show no compression artifacts . Another important advantage is the potentially larger color gamut. While JPEG images are saved with 8 bits (= 256 levels) per color channel, raw data are available in ten, twelve (= 4096 levels) or 14 bits (= 16,384 levels). The images can therefore be output in finer color gradations under certain circumstances .

### Video recording

Almost all cameras also offer the option of recording video sequences. Due to the necessary frame rate, however, always in a lower resolution than the still images that can be recorded by the camera. In the past, the video resolution was mostly below that of the video cameras commonly used at the time , but now HD resolutions up to Full HD (i.e. 1920 × 1080 pixels) are achieved almost without exception . Some consumer models, such as the GoPro Hero 3 , even support 4k recordings . While in earlier models the videos were mostly saved in the computing time-saving, but memory-intensive Motion JPEG format, highly effective compression formats such as MPEG-4 and H.264 are now mostly used. Otherwise, the video sequences can be converted into a more efficient format after being transferred to the computer.

Until the Nikon D90 was released in 2008, the system did not allow video recording for single-lens reflex cameras. Newer cameras like the Nikon D3s or the Canon EOS 550D can also record HD videos.

For a long time, most digital cameras were able to zoom, but not (re) focus, while recording video. In addition, they usually did not carry out any white balance or brightness adjustment during the recording. In the meantime (as of 2015) there are more and more cameras that are no longer inferior to camcorders in this regard.

Geotagger "Solmeta N2 Compass" for Nikon cameras with storage of the viewing direction (heading)

Digital cameras embed so-called meta information in the image data , which is specified in the Exif standard. This Exif metadata can be found in the header of the file. Many image processing programs and special tools can read out and display this data. They are also used for the exposure of the digital image on photo paper in the photo laboratory. The parameters automatically saved for each shot via Exif include, for example, date and time, exposure time , aperture number , exposure program , exposure index (according to ISO), focal length , white balance or use of the flash.

Some cameras support geo-imaging by means of a built-in or additionally connected GPS module and can save information about the location, for example geographical longitude and latitude as well as GPS altitude, GPS time or GPS viewing direction.

## Storage media

Sony Mavica FD5: Floppy disk as storage medium
CompactFlash memory card

The images are saved in the camera on various storage media . In particular, various types of memory cards and the microdrive were in use ; older digital cameras also used floppy disks , PCMCIA / PC cards or compact discs . The majority of digital cameras now use (micro) SD cards (as of 2015).

At times there were also digital cameras with SDRAM as memory. However, this type of data backup turned out to be impractical because the SDRAM had to be permanently supplied with energy. This meant that the standby time with inserted batteries was quite short. If the power supply was interrupted, the saved data was lost. To prevent this loss of data, some models had a capacitor that continued to supply the RAM with energy in the event of a battery change. If this was not done before the capacitor was discharged, the stored data would also be lost. Cameras of this design were characterized above all by their low production costs.

## Device interfaces

As a hardware interface, the Universal Serial Bus has largely established itself in the user area . The camera usually makes the data available to the PC either as a "mass storage device" (see USB mass storage device ) or in PTP mode. Some (mostly older) devices still require manufacturer-specific software for the transfer. Computer-controlled triggering is also possible with some cameras via the PTP mode, but in the rarest cases with full control over exposure time , f-number , zoom , focus and ISO number .

Many digital cameras can also be connected directly to photo printers via USB for printing if both devices support the PictBridge standard. Since 2006, cameras have increasingly offered the option of wireless data transmission such as WLAN or Bluetooth .

## Digital cameras for children

Digital cameras that are marketed for children are characterized by the fact that comparatively simple technology is built into relatively robust and shock-resistant, sometimes water-protected housing. They are often larger and designed so that they can be held with both hands in order to accommodate the as yet untrained fine motor skills of children. Often they also have two search windows so that the children don't have to turn a blind eye. The photographic possibilities of such cameras are usually very limited, since they usually only have a low image resolution, no optical zoom and usually no distance adjustment option.

## Digital cameras for animals

Curious pet owners developed digital cameras that document every step their four-legged friend takes. The cameras are particularly light in weight so that they do not disturb the animal . They are attached to the collar and you can see everything from the perspective of the pet . Most of these cameras have both a photo and a video function, with the quality and exact functions varying depending on the manufacturer.

## distribution

Distribution of digital cameras in Germany
year Equipment
Degree duration
2004 19.4 21.3
2005 31.9 36.1
2006 41.8 48.9
2007 48.7 59.4
2008 58.3 73.3
2009 64.1 85.1
2010 67.7 91.8
2011 71.7 100.6
2012 72.8 103.2
2014 75.6 109.0
2015 75.1 107.2
2016 73.6 105.1

In Germany, 73.6% of households have a digital camera (as of 2016). These households have more than 2 digital cameras on average.

## Sales forecasts

In September 2015, the digital association Bitkom published forecasts for the German market, according to which digital cameras are expected to generate total sales of EUR 1.09 billion for 2015 as a whole. The sales figure is estimated at around 3.38 million devices. According to Bitkom, anyone who buys a digital camera is now paying more than a few years ago: Today the average price for a digital camera is 323 euros. In 2012 it was less than 240 euros.

## literature

Commons : Digital Cameras  - Collection of Images
Wiktionary: digital camera  - explanations of meanings, word origins, synonyms, translations

## Individual evidence

1. Patent US3540011 : All solid state radiation imagers. Applied on September 6, 1968 , published on November 10, 1970 , inventors: Edward H. Stupp, Pieter G. Cath, Zsolt Szilagyi.
3. 1969 - Invention of the CCD sensor , image of the two CCD inventors with their live camera , sueddeutsche.de, November 24, 2008, accessed online on November 15, 2012
4. ^ McCord, Thomas B. and Westphal, James A. (1972) Two-Dimensional Silicon Vidicon Astronomical Photometer. Applied Optics, 11 (3). pp. 522-526.
5. ^ Westphal and McCord, 1972
6. Patent US4163256 : Electronic photography system. Applied June 27, 1972 , published July 31, 1979 , inventor: Willis A. Adcock.
7. ^ Electrical Design News, vol. 18, 1973
8. Steve Sasson: We Had No Idea  ( page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. .  October 16, 2007, accessed May 13, 2008.
9. Pitzke, M. (2015) First digital camera - The man who invented the future . Spiegel Online, October 27, 2015.
10. a b Digital cameras in the test: You can find the best camera here , test.de from March 2, 2018, accessed on April 19, 2018
11. Photo boom: Five million digital cameras sold ( Memento of the original from July 4, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , chip.de of April 27, 2004, accessed online on October 1, 2012
12. Nikon ceases production of most of its analog cameras. (News report) In: Heise-Online. January 12, 2006, accessed April 30, 2009 .
13. Digital camera - four megapixels in focus , test.de , accessed online on October 1, 2012
14. Pixel race at the restart , test.de , accessed online on October 1, 2012
15. Pixel madness with consequences , test , March 2007 edition, pages 56 to 61
16. Less would be more , test , September 2007 edition, pages 46 and following
17. Smartphone with 41-megapixel camera - sluggish camera despite pixel madness , test.de , accessed online on October 1, 2012
18. Nikon: Coolpix P900 , test.de from May 22, 2015, accessed on April 19, 2018
19. New product under test - digital camera and camcorder in one device , test.de , accessed online on October 2, 2012
20. APS camera with photo preview - weak performance , test.de (June 2001), accessed online on October 2, 2012
21. News from CES 2013 ( Memento of the original from January 12, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed online January 9, 2013
22. Image sensors in digital cameras. Retrieved August 29, 2014 .
23. New Foveon layer sensor with higher resolution. Retrieved August 27, 2014 .
24. Telltale traces, even digital cameras leave fingerprints. In: Thomas Reintjes, Deutschlandradio. August 7, 2015, accessed July 23, 2019 .
25. Carsten Meyer: Dives into: Rollei compact camera X-8 Sports. (News report) In: Heise-Foto. August 29, 2008. Retrieved April 30, 2009 .
26. Michael Ludwig: http://www.chip.de/artikel/Systemkamera-Die-besten-spiegellosen-Kameras-im-Test_43394276.html The new camera stars CHIP, July 5, 2011, accessed on April 22, 2011
27. Carsten Meyer: For something new: Samsung system camera NX10 . heise photo, January 7, 2010, accessed on March 16, 2010 (news item).
28. ^ K-01 description on the Pentax website ( Memento of August 8, 2012 in the Internet Archive ), last accessed on February 19, 2012.
29. Sony Alpha SLT-A58: digital camera with partially transparent mirror. Sony, accessed January 5, 2012 .
30. ^ For example, Panasonic Lumix DMC-SZ10 , data sheet from dkamera.de, accessed on April 26, 2019
31. a b c camera calculations on vision-doctor.com and pixel size calculator lcdtech.info, data entered for the 16MP 1 / 2.3 inch sensor were 4608 * 3456 pixels on 0.3042 inch sensor diagonal (corresponds to 7.7 mm - see common format factors ) = 1.35 µm; with the 123 MP of the Mamiya-ZD medium format sensor, the data 12800 * 9624 were used on a 4: 3 sensor with a 2.3622 inch diagonal (corresponds to 60mm) = 3.75 µm pixel size; with 61 MP of a 3: 2 KB sensor, the data 9600 * 6400 pixels on a 1.7047 inch diagonal (corresponds to 43.3 mm) were used = 3.75 µm pixel size; accessed on April 26, 2019
32. a b Image recording , digital imaging methods, Wikibooks - the free library, chapter "Critical aperture", section "Calculation on a plano-convex lens", formula: d = 2.44 * 550nm * k = 1.342µm * k (where k is the aperture number and d is the diameter of the diffraction disk, calculated at a typical green wavelength of 550 nanometers)
33. a b Beugung, Diffraction , Diffraktion, foto-schuhmacher.de, accessed on April 22, 2019
34. ↑ Using old lenses on new cameras , pcwelt.de, author: David Wolski, as of May 3, 2012, accessed on December 3, 2017
35. With a typical aspect ratio of 3: 2 for 35mm full-format sensors, 87 megapixels correspond to a resolution of 11424x7616 pixels according to rechneronline.de . With a 1.7047 inch sensor diagonal (this corresponds to 43.3mm of a typical KB sensor), the result is a pixel size of 3.15 µm (in height and width) according to vision-doctor.com . With this data, Bayer color sensors achieve 79.36 lp / mm (500 / (3.15 µm * 2) = 500 / 6.4 = 79.36 lp / mm) according to OptoWiki .
36. With a typical aspect ratio of 3: 2 for 35mm full-format sensors, 44 megapixels correspond to a resolution of 8124x5416 pixels according to rechneronline.de . With a 1.7047 inch sensor diagonal (this corresponds to 43.3mm of a typical KB sensor), the result is a pixel size of 4.43 µm (in height and width) according to vision-doctor.com . With this data, monochrome sensors achieve 80 lp / mm (500 / (4.43 µm * 1.41) = 500 / 6.25 = 80 lp / mm) according to OptoWiki .
37. Conversion of pixel size into line pairs per millimeter , OptoWiki.info, knowledge database for technical optics; Formula for color sensors: line pairs per millimeter = 500 / (pixel size in µm * 2); Formula for monochrome sensors: line pairs per millimeter = 500 / (pixel size in µm * 1.41); accessed on May 13, 2019
38. Google Pixel: How does night vision work? t3n.de, Google increases the photo quality of its camera in Pixel 3 and older devices with a pure software update, Author: Andreas Floemer, accessed on December 26, 2019
39. Galaxy S10 + - night mode - sample photos, samsung.com, a photo gallery that shows the possibilities of the tricky creation of such photos; these possibilities were also made possible by a pure software update, accessed on December 26, 2019
40. a b c Test report: Sony Alpha 7R IV , digitalkamera.de, page 2, November 15, 2019, tested on the lens “Sony FE 24-105 mm F4 G OSS”, author: Benjamin Kirchheim, accessed on December 23, 2019
41. a b The 50-megapixel full-format lie , docma.info, author: Christoph Künne, as of February 20, 2015, quote: According to measurements by DXOmark.com, for example, the Nikon D800 already has 29 megapixels (MP) A full-format camera should not have a resolution of more than 24 MP, an APS-C camera theoretically only nine and a sensor in 4/3 format five MP ; for full-frame cameras see also the section Update , quote: at DXOmark, the Nikon D800E and the D810 with the Zeiss Otus 55 have also been tested: 33 MP resolution with the 36 MP chip; the Otus 85 even has a resolution of 35 MP on the D810 , accessed on November 13, 2017
42. ↑ Are megapixels replacing zoom lenses? , Quote: The higher the resolution, the sooner the sensor reveals only weaknesses in the optics and every slightest vibration and unrest of the camera , accessed on November 13, 2017
43. a b c d Sensor noise, noise in photos, image noise , Author: Dr. Shoemaker, accessed November 13, 2017
44. Test report Sony Alpha 7R II , comparison of the image quality between a7II (24MP) and a7rII (42MP) in the test laboratory of digitalkamera.de, Author: Benjamin Kirchheim, as of September 29, 2015, page 2 image quality, accessed on December 8, 2017
45. a b High-ISO resolution comparison of the Sony Alpha 9 and Alpha 7R III , digitalkamera.de, February 2, 2018, accessed on March 14, 2019; The Sony Alpha 7S is not part of the title, but is used in the article for the comparison test.
46. a b c d Photo tip: Reduce the number of pixels , Stiftung Warentest, accessed on November 14, 2017
47. How much resolution do I really need? Version 2.0c, slr-foto.de, see the sections demosaicing method and image reduction , accessed on November 13, 2017
48. How much resolution do I need and when? , accessed November 14, 2017
49. PureView: This is how Nokia's new camera technology works , focus online, accessed online on October 1, 2012
50. Markus Bautsch: Contrast Sensitivity Function, Wikibook: Digital Imaging Methods - Basics , accessed online on January 18, 2013
51. Photo GPS with compass - what for? ( Memento from March 22, 2014 in the Internet Archive ) gps-camera.eu, accessed on November 25, 2009 (via automatic storage of the compass viewing direction in the Exif header).
52. Mini camera for animals: cats spy on their neighbors. Retrieved August 29, 2014 .
53. Pet camera. Retrieved August 29, 2014 .
54. a b c Furnishing private households with selected consumer goods - Fachserie 15 Row 2. (No longer available online.) In: destatis.de. 2012, archived from the original on November 15, 2013 ; Retrieved December 16, 2010 .
55. ^ Equipping private households with selected consumer goods - Fachserie 15 Reihe 2 - 2016. In: destatis.de. 2016, accessed March 16, 2017 .
56. In… out of 100 households there is a digital camera.
57. There are… digital cameras in 100 households.
58. Smartphones, tablets and wearables get entertainment electronics going . Bitkom press release of September 1, 2015, accessed on September 30, 2015.
59. ↑ Consumer electronics market shrinks by 3.8 percent in 2015 . ZDNet.de, September 1, 2015, accessed on September 30, 2015.
60. Guideline for tests of digital cameras published ( Memento of the original from 23 August 2014 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , DIN.de, accessed online on March 5, 2013