Archived posting to the Leica Users Group, 2001/02/07

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Subject: RE: Re: [Leica] how can the 75 Lux focus go bad?
From: "" <>
Date: Wed, 7 Feb 2001 08:11:55 -0500

I disagree.  If you take the same lense, and use it on ANY size film, at the same distance, you will get the same DOF.  Optics doesn't know what the film size is, and adjust it self accordingly.  3' IS 3', no matter what the film size is.

I don't disagree that if you change the distance, to re-frame the image so it is the same composition you will get different DOF, but that is not part of the discussion...the DOF calculator keeps the same distance, just changes in the film format change the resultant DOF it gives you.  I believe that is wrong.

> Depth of field is a factor of image size and relative aperture. The film
> format/ lens combination affects the image size. A 45mm lens in on a 4x5
> camera will record an object "smaller" in the final print than a 45mm on a
> 35mm camera. You could enlarge the 4x5 negative more than normally is done
> and print an identical image size (assuming you shot both cameras at the
> same subject distance) and achieve identical depth of field (and COC) but
> this is not normal practice.

>> This web page changes the DOF based on film format...why would film format
>> effect DOF?

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Replies: Reply from "Jason Hall" <> (Re: Re: [Leica] how can the 75 Lux focus go bad?)
Reply from Jim Brick <> ([Leica] Re: DOF)