DOF and Cropping take 2

Started Feb 11, 2014 | Discussions thread
MightyMike Forum Pro • Posts: 37,671
Re: DOF and Cropping take 2

awaldram wrote:

moving_comfort wrote:

Q: Does cropping FF (to ap-sc, for example) change DOF when displayed at the same sizes? Because I think you used to hold the position that it does not.

You missed the point!

Does cropping FF (to ap-sc, for example) change DOF when displayed at the same sizes?

To crop and then display at the same size the magnification must change and therefore the appearance of DOF will change!

Simple question how can it.?

The lens projects an image onto the film plane that image is the same whatever sensor is behind it

look at it this way assume we have a camera with interchangeable backs.

We put a 50mm f4 lens on the camera on a tripod with a FF back on it and take a picture.

we then do nothing but change the back to a sensor 1/2 the size and take another picture.

if we superimpose the two images on-top of each other will the be different in any way shape or form where they overlap?

I think your not totally mad so we'll assume you said yes at this point.

you now take the FF image cut that middle 50% out do you now have to identical image and is DoF the same ?

As I've tried in vain to point out it only because your viewing position alter across formats does the DoF appear different exactly the same as why a telephoto appears to have a shorter dof than wide angle.


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