Crop Factor
A number that shows how much more tightly a lens frames a scene on a smaller sensor than on a full-frame camera.
On this page 3 sections
A lens's focal length, written in millimetres, describes how wide or how zoomed-in its view is. Those numbers are based on full-frame cameras. When the same lens is used on a smaller sensor, the sensor records only the central part of the image, so the view looks more zoomed in. The crop factor is the number that tells you by how much.
Common crop factors
- Full-frame: 1, the reference point.
- APS-C: about 1.5, or about 1.6 on some systems. A 50 mm lens frames like a 75 to 80 mm lens on full-frame.
- Four Thirds: about 2. A 50 mm lens frames like a 100 mm lens on full-frame.
How it is used
Multiplying a focal length by the crop factor gives the full-frame equivalent, often written as the 35 mm equivalent. This lets two lenses on different cameras be compared by how wide or tight their view is. A figure that is already given as an equivalent is not multiplied again.
What it does not promise
The crop factor describes framing, not the lens itself. It does not add detail, because the sensor simply records a smaller part of what the lens projects. A smaller sensor also gives less background blur at the same framing and lens opening than a full-frame camera.