Archived posting to the Leica Users Group, 2004/02/16

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Subject: [Leica] Oh god please no! Not DOF again
From: John Collier <jbcollier@shaw.ca>
Date: Mon, 16 Feb 2004 17:07:31 -0700

It is not rocket science folks. DOF is an illusion. There is only one 
plane of sharpness. It is an effective illusion none-the-less.

Perceived DOF depends on these factors:

1) size of the aperture

2) actual object magnification

3) lens/medium performance

That is it. Nothing else matters

1) The size of the aperture is something we all should easily agree on. 
Large aperture means narrow DOF and small aperture means large DOF. I 
cannot remember, and am too lazy to look it up, if it is the relative 
aperture (the F number) or actual aperture (physical size) that is the 
important one but someone will chime in I am sure.

2) This takes into account focal length, focused distance, enlargement 
and viewing distance.

3) Soft lenses, small sensors, coarse film all reduce the output 
resolution which makes small changes in sharpness difficult to discern 
therefore increasing the apparent DOF (A wider band of crap so to 
speak). Sharp lenses, large sensors, fine film all increase the 
resolution which makes small changes in sharpness easily apparent 
therefore smaller apparent DOF.

John Collier

Oh how I dread the inevitable rebuttals. Please, please, please do your 
research before you open your mouth and prove yourself an...

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Replies: Reply from Brian Reid <reid@mejac.palo-alto.ca.us> (Re: [Leica] Oh god please no! Not DOF again)
Reply from Henning Wulff <henningw@archiphoto.com> (Re: [Leica] Oh god please no! Not DOF again)
Reply from "Jacques Bilinski & Barbara Bradbury" <jbilin@axionet.com> (Re: [Leica] Oh god please no! Not DOF again)
Reply from JCB <jcb@visualimpressions.com> ([Leica] Re: Oh god please no! Not DOF again)