Crop Factor by Sensor Size

Crop factor compares a sensor's diagonal with that of the 35 mm frame, which became the reference for having dominated cinema and photography for decades. A smaller sensor sees a smaller piece of the image the lens projects, and the effect is the same as cropping the photograph — hence the name.

Pick the format and the page returns the factor. The values cover what you will meet: full frame at 1, APS-C at 1.5 on Nikon, Sony and Fuji and 1.6 on Canon, micro four thirds at 2, one inch at 2.7 and medium format at 0.79 — that last one below 1, because the sensor is larger than the 35 mm frame and sees more, not less.

The factor is used by multiplying the focal length to learn the equivalent framing, but it does not change the lens: a 50 mm stays a 50 mm, with the same physical aperture. What changes beyond framing is depth of field — for the same framing and the same nominal aperture, the smaller sensor keeps more in focus, because the real focal length is shorter.