I was reading about crop factors that for example a Polaroid land camera on f/3.2 lens is something around f/1.4 equivalent in 35mm film including the crop factor. ( Until now I was under impression that crop factor only affect the focal point ).

So does that mean when I am measuring with a light meter, should I convert the f number too depending on the crop factor and use that new value for the light meter readings?


2 Answers 2


No, the light meter reading (for example, ISO 100, f/11, 1/200 second) already applies to any camera, any sensor size, any crop factor. That''s the beauty of the "f/stop" numbering system.

Crop factor might apply to focal length and sensor size situations, but Not to exposure.


No correction is needed. The image formed by the lens is still that of a lens of the nominal focal length. You can use a lens designed for a full frame body on a cropped-frame body, but the image formed by the lens won't change because you put a body with a smaller sensor behind it.
What changes is the part of the image that is used: a sensor smaller than 24×36 mm only uses the center of the image, and thus has a field of view that is smaller than for a full-frame (24×36 mm) sensor. The crop factor expresses this, and only this.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.