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Re: [OM] More on DOF and focal length (by Ctein)

Subject: Re: [OM] More on DOF and focal length (by Ctein)
From: Ken Norton <ken@xxxxxxxxxxx>
Date: Sat, 27 Jun 2009 14:29:49 -0500
>
> Normally said as "all wet" rather than "completely wet".  At least I
> think that's what he meant.  See definition #2 here:
> <http://en.wiktionary.org/wiki/all_wet>
>


I think his conclusion is correct, but the path to get there is wrong. The
math does not match his assumptions--especially in the discussion about
cropped image vs longer focal-length. This is when his theories break down
because as Chuck has clearly stated, in order to calculate DoF you must work
from a known output size (magnification).  Ctein is using "non-test tests to
figure this out and is being fooled by how different optical designs can
alter other imaging characteristics which can be misinterpreted as an
increase/decrease in DoF.

AG
-- 
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