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 sensor. Because the image sensors in many digital cameras is smaller than the 24 mm × 36 mm image area of full-frame 35 mm cameras, a lens of a given focal will give a narrower field of view on such cameras.
The size of a sensor is often expressed as optical format in inches. Other measures are also used; see table of sensor formats and sizes 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 film format results in cropping of the image. This latter effect is known as field of view crop. The format size ratio (relative to the 35 mm film format) is known as the field of view crop factor, crop factor, lens factor, focal length conversion factor, focal length multiplier or lens multiplier.
Three possible depth of field comparisons between formats are discussed, applying the formulae derived in the article on depth of field. The depths of field of the three cameras may be the same, or different in either order, depending on what is held constant in the comparison.
Considering a picture with the same subject distance and angle of view for two different formats:
so the DOFs are in inverse proportion to the absolute aperture diameters and .
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