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Image sensor format
In digital photography, the image sensor format is the shape and size of the image sensor.
The image sensor format of a digital camera determines the angle of view of a particular lens when used with a particular camera. In particular, image sensors in digital SLR cameras tend to be smaller than the 24 mm x 36 mm image area of full-frame 35 mm cameras. Larger image sensors typically produce higher-quality images (see below).
Lenses produced for 35 mm film cameras may mount well on the digital bodies, but the larger image circle of the 35 mm system lens allows unwanted light into the camera body, and the smaller size of the image sensor compared to 35 mm format results in cropping of the image compared to the results produced on the film camera. This latter effect is known as field-of-view crop; the format size ratio is known as the crop factor or focal-length multiplier.
Additional recommended knowledge
Larger sensors capture images with less noise and greater dynamic range than smaller sensors. The desirable properties of signal-to-noise ratio and sensor unity gain both scale with the square root of sensor area.
As of December 2007, many DSLRs have sensor areas around 370 mm2, while many compact camera sensors have one-fifteenth the surface area: a standard 1/2.5" sensor has a surface area of 24.7 mm2. Thus, a typical DSLR will have a signal-to-noise ratio that is nearly 4 times higher than a compact digital camera ().
Because of their larger sensors, DSLRs can generally take high-quality pictures at ISO 1600, 3200, or even higher speeds, while compact cameras tend to produce grainy images even at ISO 400. This problem is exacerbated by pixel count; doubling the number of pixels on the sensor means that each pixel is half the size, and hence will be noisier.
Common image sensor formats
Digital SLR formats
As of December 2007, most consumer-level SLRs use sensors around the size of a frame of APS-C film, with a crop factor of 1.5-1.6 or slightly smaller. A notable exception is the Four Thirds System of cameras, mostly made by Olympus, which use smaller sensors with a crop factor of 2.0.
Most DSLR image sensor formats approximate the 3:2 aspect ratio of 35 mm film. Again, the Four Thirds System is a notable exception, with an aspect ratio of 4:3 as seen in most compact digital cameras (see below).
Some professional DSLRs use full-frame sensors, equal to the size of a frame of 35 mm film.
Medium-format DSLR formats
The most common sensor size for medium-format digital cameras is approximately 36 × 48 mm, due to the widespread use of Kodak's 22-megapixel KAF-22000 and 39-megapixel KAF-39000 CCDs in that format.
Compact digital camera formats
Many compact digital cameras use sensors with formats specified in the "inch" system, derived from the outside diameter of the glass envelope of the video camera tube that supported that image size. These formats are often called types, as in "1/2-inch-type CCD."
Most compact image sensor formats have an aspect ratio of 4:3. This matches the aspect ratio of the popular VGA, SVGA, and XGA display resolutions, allowing images to be displayed on most computer monitors without cropping.
As of December 2007, most compact digital cameras use 1/2.5" size sensors. Recent digicams with this sensor size include the Panasonic Lumix DMC-FZ18, Canon PowerShot A570 IS, Canon SD870 IS Digital ELPH (IXUS 860 IS), Sony Cyber-shot DSC-W80, Canon Powershot S5is, Sony Cyber-shot DSC-H7, Canon PowerShot TX1, Sony Cyber-shot DSC-H9, and Casio Exilim EX-V7.
Three recent digicams using slightly larger sensors are the Canon PowerShot G9 (1/1.7"), Ricoh Caplio GX100 (1/1.75"), and the Nikon Coolpix P5000 (1/1.8").
Table of sensor sizes
Since inch-based sensor formats are not standardized, exact dimensions may vary, but those listed are typical.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Image_sensor_format". A list of authors is available in Wikipedia.|