Archived posting to the Leica Users Group, 1998/04/10

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Subject: Re: [Leica] TC-DOF? Optical wizards?
From: Jim Brick <jim@brick.org>
Date: Fri, 10 Apr 1998 08:04:56 -0700

Using a ND filter (actually any filter, including a UV) doesn't change your
DOF. The DOF is controlled by the focal length/diaphragm/circle of
confusion/depth of focus factors. Not another piece of glass in the lens
element chain. Thinking about the situation leads me to believe that a 360
set at 5/6 and a 180 + 2x with lens set at 2.8, will yield the same DOF. If
this is wrong, I would indeed like to know why. Erwin?

Jim


At 07:46 AM 4/10/98 -0400, you wrote:
>Optical wizards all...a question:
>
>Will the depth of field available with a (mythical) Leica 360/4 lens set
>at 5.6 be exactly equal to the depth of field available using a Leica
>180/2.8 and the 2x converter at max aperture? Or (answering my own
>question) would the depth of field for the 180/2x combination result in
>depth of field exactly equal to a 360/2.8 with a 2-stop neutral density
>filter?
>
>I have the 2x Apo converter, but am thinking, for DOF reasons alone,
>that I need long primes. Ouch.
>
>Curious in Annapolis, I remain,
>
>David W. Almy
>