

Three possible depth-of-field comparisons between formats are discussed, applying the formulae derived in the article on depth of field. 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. This latter effect is known as field-of-view crop. 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. Other measures are also used see table of sensor formats and sizes below. Sensor size is often expressed as optical format in inches. Because the image sensors in many digital cameras are smaller than the 24 mm × 36 mm image area of full-frame 35 mm cameras, a lens of a given focal length gives a narrower field of view in such cameras.

The image sensor format of a digital camera determines the angle of view of a particular lens when used with a particular sensor. In digital photography, the image sensor format is the shape and size of the image sensor. For broader coverage of this topic, see Image sensor.
