Archived posting to the Leica Users Group, 2001/02/08

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Subject: Re: [Leica] Re: DOF -Optical vs Apparent
From: "R. Saylor" <rlsaylor@ix.netcom.com>
Date: Fri, 9 Feb 2001 01:23:21 -0500
References: <006401c09244$77c9a8f0$617079c0@drt4>

DOF is objective. It is based on a perfect lens in which a 
mathematical point in the plane of focus is projected as a 
mathematical point on the image.  Nearer or farther than the plane 
of focus, a point will appear (roughly) as a circle rather than a point. 
The maximum acceptable diameter of this circle is chosen as the 
circle of confusion for DOF computations, which are based on 
theoretical optical considerations. I believe Zeiss uses 0.025mm and 
Leica 0.033mm for the COC in the computations for their DOF 
scales.  It is all theoretical, based on a perfect lens, and has nothing 
to do with the resolution of a specific lens.

Richard

In reply to: Message from "Austin Franklin" <austin@darkroom.com> (RE: [Leica] Re: DOF -Optical vs Apparent)