Most current consumer digital cameras use a Bayer filter mosaic in combination with an optical anti-aliasing filter to reduce the aliasing due to the reduced sampling of the different primary-color images. A demosaicing algorithm is used to interpolate color information to create a full array of RGB image data.
Cameras that use a beam-splitter single-shot 3CCD approach, three-filter multi-shot approach, Color co-site sampling or Foveon X3 sensor do not use anti-aliasing filters, nor demosaicing.
Firmware in the camera, or a software in a raw converter program such as Adobe Camera Raw, interprets the raw data from the sensor to obtain a full color image, because the RGB color model requires three intensity values for each pixel: one each for the red, green, and blue (other color models, when used, also require three or more values per pixel). A single sensor element cannot simultaneously record these three intensities, and so a color filter array (CFA) must be used to selectively filter a particular color for each pixel.
The Bayer filter pattern is a repeating 2×2 mosaic pattern of light filters, with green ones at opposite corners and red and blue in the other two positions. The high proportion of green takes advantage of properties of the human visual system, which determines brightness mostly from green and is far more sensitive to brightness than to hue or saturation. Sometimes a 4-color filter pattern is used, often involving two different hues of green. This provides potentially more accurate color, but requires a slightly more complicated interpolation process.
The color intensity values not captured for each pixel can be interpolated (or guessed) from the values of adjacent pixels which represent the color being calculated.
Sensor size and angle of view
Cameras with digital image sensors that are smaller than the typical 35mm film size have a smaller field or angle of view when used with a lens of the same focal length. This is because angle of view is a function of both focal length and the sensor or film size used.
If a sensor smaller than the full-frame 35mm film format is used, as in most digicams, then the field of view is cropped by the sensor to smaller than the 35mm full-frame format's field of view. This narrowing of the field of view is often described in terms of a focal length multiplier or crop factor, a factor by which a longer focal length lens would be needed to get the same field of view on a full-frame camera.
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The result is geometrically similar to taking the image from the film camera and cutting it down (cropping) to the size of the sensor, ignoring various questions such as resolution. For moderately large DSLRs the crop factor may be in the range of 1.3-2 while smaller cameras use smaller sensors with a larger crop factor.
If the digital sensor has a higher or lower density of pixels per unit area than the film equivalent, then the amount of information captured differs correspondingly. While resolution can be estimated in pixels per unit area, the comparison is complex since most types of digital sensor record only a single colour at each pixel location, and different types of film have different effective resolutions. There are various trade-offs involved, since larger sensors are more expensive to manufacture and require larger lenses, while sensors with higher numbers of pixels per unit area are likely to suffer higher noise levels.
For these reasons, it is possible to obtain cheap digital cameras with sensor sizes much smaller than 35mm film, but with high pixel counts, that can still produce high-resolution images. Such cameras are usually supplied with lenses that would be classed as extremely wide angle on a 35mm camera, and that can also be smaller size and less expensive, since there is a smaller sensor to illuminate. For example, a camera with a 1/1.8" sensor has a 5.0x field of view crop, and so a hypothetical 5-50mm zoom lens produces images that look similar (again the differences mentioned above are important) to those produced by a 35mm film camera with a 25–250mm lens, while being much more compact than such a lens for a 35mm camera since the imaging circle is much smaller.
This can be useful if extra telephoto reach is desired, as a certain lens on an APS sensor produces an image equivalent to a significantly longer lens on a 35mm film camera shot at the same distance from the subject, the equivalent length of which depends on the camera's field of view crop. This is sometimes referred to as the focal length multiplier, but the focal length is a physical attribute of the lens and not the camera system itself. The disadvantage of this is that wide angle photography is made somewhat more difficult, as the smaller sensor effectively and undesirably reduces the captured field of view. Some methods of compensating for this or otherwise producing much wider digital photographs involve using a fisheye lens and "defishing" the image in post processing to simulate a rectilinear wide angle lens.
Full-frame digital SLRs, that is, those with sensor size matching a frame of 35mm film, include Canon 1D X, 1Ds and 5D series; Kodak Pro DCS-14n; Nikon D3, D4 and D800 lines; and Contax N Digital. There are very few digital cameras with sensors that can approach the resolution of larger-format film cameras, with the possible exception of the Mamiya ZD (22MP), the Hasselblad H3D series of DSLRs (22 to 39 MP), and the Nikon D800 (36 MP).
Common values for field of view crop in DSLRs include 1.3x for some Canon (APS-H) sensors, 1.5x for Sony APS-C sensors used by Nikon, Pentax and Konica Minolta and for Fujifilm sensors, 1.6 (APS-C) for most Canon sensors, ~1.7x for Sigma's Foveon sensors and 2x for Kodak and Panasonic 4/3" sensors currently used by Olympus and Panasonic. Crop factors for non-SLR consumer compact and bridge cameras are larger, frequently 4x or more.
| Table of sensor sizes | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Type | Width (mm) | Height (mm) | Size (mm²) | |||||||||||
| 1/3.6" | 4.00 | 3.00 | 12.0 | |||||||||||
| 1/3.2" | 4.54 | 3.42 | 15.5 | |||||||||||
| 1/3" | 4.80 | 3.60 | 17.3 | |||||||||||
| 1/2.7" | 5.37 | 4.04 | 21.7 | |||||||||||
| 1/2.5" | 5.76 | 4.29 | 24.7 | |||||||||||
| 1/2.3" | 6.16 | 4.62 | 28.5 | |||||||||||
| 1/2" | 6.40 | 4.80 | 30.7 | |||||||||||
| 1/1.8" | 7.18 | 5.32 | 38.2 | |||||||||||
| 1/1.7" | 7.60 | 5.70 | 43.3 | |||||||||||
| 2/3" | 8.80 | 6.60 | 58.1 | |||||||||||
| 1" | 12.8 | 9.6 | 123 | |||||||||||
| 4/3" | 18.0 | 13.5 | 243 | |||||||||||
| APS-C | 25.1 | 16.7 | 419 | |||||||||||
| 35 mm | 36 | 24 | 864 | |||||||||||
| Back | 48 | 36 | 1728 | |||||||||||
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