Archived posting to the Leica Users Group, 1996/04/23

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To: Marc James Small <msmall@roanoke.infi.net>, leica-users@mejac.palo-alto.ca.us
Subject: Re: Minimum aperture question:
From: beamon@primenet.com (Roger L. Beamon)
Date: Tue, 23 Apr 1996 16:55:30 -0700 (MST)
Cc: beamon@primenet.com (Roger L. Beamon)
 
At 06:44 PM 4/23/96 -0400, Marc James Small wrote:
>Below a certain point, diffraction begins to degrade image quality.  I
>recognize most Leica RF lenses of recent (post-1950) vintage only stop to
>f/16:  I'd guess this was to keep the degradation of image quality in line.

Right, Marc, I know of the diffraction that manifests with small apertures,
but I wonder how they decide where to stop. Interesting that minimum
apertures vary considerably depending, I guess, on design (elements/groups)
and the manufacturer's willingness to accept a certain amount of diffraction
degradation. 

Couple that with Leica's oft discussed "purposeful coma allowance" on
certain lenses and you have that very complicated, elusive and impossible to
understand "Leica look"!
       --
       Roger Beamon,  Natural History Interpreter & Photographer
                                 Docent: Arizona-Sonora Desert Museum
                                 INTERNET: beamon@primenet.com