Dictionary of Computer and Internet Terms: crop factor
crop factor
the factor by which the image sensor of a DSLR camera is smaller than the film for which the camera's lenses were designed. For example, on 35-mm film, each picture is 24×36 mm. If a DSLR has an image sensor half as big, 12×18 mm, it will have a crop factor of 2. Popular DSLRs actually have a crop factor of about 1.5.
The crop factor effectively multiplies the focal length of the lens.A 100-mm lens on a DSLR with a crop factor of 1.5 will cover the same field of view as a 150-mm lens on a 35-mm film SLR. That is, it has a "35-mm equivalent" of 150 mm.
