Crop Factor

Most digital cameras have sensors size smaller than 35mm frame. Pictures captured by a small sensor size will have a cropping effect as compared to 35mm frame. Because for this cropping effect, lens made for small sensors have shorter focal length. To measure crop factor, take the length/width/diagonal of the 35mm format divided by length/width/diagonal of the cropped sensor. In SLR, it is important to know what the crop factor is because you will need to know the correct focal length to purchase. For example, to obtain a 50mm in 35mm equivalent format, you will need to purchase a len that is about 31mm for a crop sensor of 1.6x. For compact camera, there will be a phrase “35mm equivalent” to tell consumers how wide and how far the camera can take.

For those who heard of 35mm format but wondered why the size is 36mm by 24mm is because
35mm format refers to the width of the negative film. 36mm by 24mm is the area that image will be captured.

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