Archived posting to the Leica Users Group, 1996/07/26

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To: leica-users@mejac.palo-alto.ca.us
Subject: Leica recommendations for IR film
From: Willem-Jan Markerink <w.j.markerink@a1.NL>
Date: Fri, 26 Jul 1996 22:48:43 +0000
Comments: Authenticated sender is <wjmarkerink@mail.a1.nl>
Priority: normal
 
Hi gang,

On the IR list, someone mentioned the fact that Leica, as Nikon, 
recommends closing aperture instead of using the IR focus mark. 
Assuming that most primes still have such an IR focus mark, this 
surprised me. How is this subject treated in Leica manuals?

[background: one of my technical IR books (written by Guenter 
Spitzing, a well known German author of several camera books, I 
assume about Leica as well(?)) clearly states that closing down to 
minimum aperture is not recommended due to increasing diffraction 
with increasing wavelengths (IR being longer waves than visible)]

Can anyone shed some light on this subject?


--
Bye,

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The difference 
between men and boys
is the price of their toys

<w.j.markerink@a1.nl>
[note: 'a-one' & 'en-el'!]