Archived posting to the Leica Users Group, 2003/08/26

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Subject: diffraction (was Re: [Leica] Leica 90mm f/4.0 Elmar C prices)
From: Doug Herr <telyt@earthlink.net>
Date: Tue, 26 Aug 2003 19:15:04 -0700

on 8/26/03 6:49 PM, Afterswift@aol.com at Afterswift@aol.com wrote:

> 
> In a message dated 8/26/03 5:13:37 PM, rhc3vt@hotmail.com writes:
> 
> << The Micro-NIKKOR-P 3.5/55mm, for one.  Can you explain the effect of
> diffraction on a lens such as the 9cm Elmar? >>
> 
> I have a Micro Nikkor 2.8 that does have an f32. I never noticed it because I
> never needed to use it. However, it is remarkable that both the Leitz 90 f4
> and the Micro Nikkor seemed to have overcome diffraction, even all those years
> ago. I certainly will hold onto those two lenses.
> 
> br
> 

It's not that they have overcome diffraction.  Whether f/32 is available or
not is a design compromise, to allow a greater depth-of-field and accepting
a softer overall image as a consequence.  If a lens is extremely
well-corrected for other aberations at small apertures, the design team may
allow f/32 if the diffraction effects don't soften the image as much as a
less well-corrected lens might at a larger aperture.  There is no avoiding
diffraction.

Doug Herr
Birdman of Sacramento
http://www.wildlightphoto.com


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