Thursday, February 23, 2012

Does a 35mm prime lens show the same bokeh as a 50mm prime lens on a cropped sensor?

Question

I came to know that a 50mm prime lens on a cropped sensor behaves like an 75mm prime lens.

So, does the 35mm prime lens behave like a 50mm prime lens on a cropped sensor?
If yes, then will it show the same bokeh as the 50mm lens on a cropped sensor?

Asked by Anisha Kaul

Answer

The only different between full frame and crop sensors is that the crop sensor is smaller - so the smaller sensor only sees only the center of the full frame image.

Or, another way to put it is that the picture you get from a crop sensor is the same picture you get from a full frame if you crop it and only leave the middle part.

So, does cropping effect bokeh? obviously not, but...

Cropping does have the same effect as zooming in, that's why the field of view of a Nikon APS-C at 35mm (or Canon APC-C at ~30mm) is similar to the field of view of a full frame with a 50mm lens.

And that "extra zoom" means that to fill the frame with the same subject on a crop sensor you will be at a greater distance than with a full frame - and distance to subject does effect DOF.

So, the quality and shape of the bokeh doesn't change in any way but the amount of bokeh does change (simply because distance to subject changes).

Answered by Nir

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