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Image sensor

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An image sensor is a type of transducer (an electronic device that converts one type of energy to another). This particular type of transducer converts light (visual images) to electronic signals, in essence capturing images in an electronic form: pixels. Image sensors are used in digital cameras and other imaging equipment and usually consist of an arrangement of charge-coupled devices (CCD).

Related Terms

The Foveon X3 direct image sensor is a new technology that works like film. Foveon pioneered the development of the direct image sensor using advanced developments in semiconductor design, image processing, and signal processing. Their X3 sensor directly captures red, green, and blue light at each point in an image during a single exposure. Similar to the emulsion layers used in colour film, Foveon X3 image sensors have three layers of pixels. The layers of pixels are embedded in silicon to take advantage of the fact that red, green, and blue light penetrate silicon to different depths - forming the first and only image sensor that captures full colour at every point in the captured image.
Advanced Photo System type-C should not be confused with the Advanced Photographic System (APS) camera/film system, since the former is digital and the latter is analogue. APS-C is a type of image sensor found in certain digital single lens reflex (DSLR) cameras. These sensors are smaller than the ones used for the conventional 36 mm x 24 mm (35 mm) sensor SLR cameras (also called full frame DSLR cameras). Being smaller causes a 1.x multiplier for the effect of the focal distance of the lenses, in comparison with the effect of those lenses on conventional 35 mm film SLR cameras or full frame digital SLR cameras. Several manufacturers produce cameras with an APS-C sensor and some even make lenses especially for them. These lenses are found in the Canon EF-S, Nikon DX, Pentax DA and Sigma DC ranges, to name the most popular ones. The most common multiplier ratios are 1.6 (Canon), 1.5 (Nikon, Fuji, Sony, etc.), 1.3 (Canon). (1.3 crop sensors are also sometimes called APS-H.) Most manufacturers not only produce cameras with these cropped sensors, but also offer DSLR cameras with full frame sensors.
A charge-coupled device or image sensor. It consists of an integrated circuit with an array of linked ("coupled") capacitors which are sensitive to light. In digital photography, the CCD is used to capture images, which in analogue photography would be captured on film. CCD technology is not only used in digital photography, but also in astronomy and other branches of science.
Describes how much an imaging sensor has been cropped in relation to its full-frame equivalent. It always describes how many times larger the full-frame is in relation to the cropped sensor. Take an APS-C sensor with a crop factor of 1.6, for instance. This indicates the sensor is 60% of the size of a frame of 35mm film. The crop factor is used to calculate how much of the equivalent of the full-frame field of view the cropped sensor will have with a lens. In order to calculate this, one multiplies the focal length of the lens by the crop factor. A 1.6 crop-factor, for instance, will give a 100mm lens the same field of view as a 160mm lens on a full-frame camera.
Extreme wide-angle lens that gives 180 degrees coverage and is uncorrected for curvilinear distortion so you produce a heavily distorted photograph. If the photo turns out to be rectangular or circular, and how distorted it looks, depends on the lens and the camera. There are basically two kinds of fish-eye lenses for photography: 1. Lenses that produce a circular image, typically 8 or 10mm lenses, used on 35mm cameras or full-frame digital cameras. They produce a circular image with dark corners (due to most photos being rectangular). A similar lens is available for digital cameras with a so-called "cropped sensor". To achieve the same circular effect, it's a 4.5mm lens. 2. Lenses that produce a rectangular image. These lenses enlarge the image to cover the whole rectangular frame of a photograph. They are typically 15 or 16mm lenses. On a 35mm or digital full-frame camera they produce rectangular but still heavily distorted images without dark corners. The same lenses on a digital camera with a cropped sensor will still have a distorting effect, but less so. Fish-eye lenses used to be prime lenses only, but one company has gone so far as to produce a 10-17mm fish-eye zoom lens. This lens still produces distorted, curvy images, but zooming in lessens the distortion.
A position where rays of light converge through a lens to create a sharp image. (This position is sometimes also called an "image point".) "To focus" means adjusting the distance setting on a lens to create this image point, which defines the subject sharply. With a photo camera, this is done by moving the lens physically towards or away from the film or sensor, or by moving the front of the lens towards or away from the rear part of the lens, which alters the focal length. (There are exceptions to this method: Contax, for instance, has a system where the autofocus operation actually moves the film and not the the lens.) When something is "in focus", it's sharp.
An imaging sensor with the same size as film used for the respective format of camera. See also Crop factor and APS-C.
A Global shutter exposes the entire imager simultaneously. The entire frame is exposed and begins gathering light; when the predetermined “shutter speed” has elapsed, the sensor stops gathering light and turns its current exposure into an electronic image.

Used in many CCD sensors. Global shutters are immune to effects like skew, wobble, and partial exposure.

Some CMOS sensors are configured to use global shutters - in which case they do not suffer from vertical smear, skew, wobble or partial exposure.