Archived posting to the Leica Users Group, 1998/04/06

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Subject: Re: [Leica] Lens evaluations
From: Dan Cardish <dcardish@microtec.net>
Date: Mon, 06 Apr 1998 09:19:36 -0400

At 02:54 PM 06-04-98 +0200, Irwin wrote:
[snip]
>The new lenses for the Contax were the result of a fresh look at those
>physical parameters within lens design that really could have direct
>relevance for the human perception of optical qualities.
>So it had been noted that microcontrast around 10 lp/mm had the most impact
>on the perception of sharp subject outlines and added to the general
>impression of briliance in a picture. It was also noted that a very high
>resolution in fact detracted from the perception of image clarity and the
>clear rendition of fine details, including subtle gradations in small
>object areas. Again the fine delineation of subject matter in strong
>highlights and deep shadows adds to the impact of a picture. [snip]

I often  look at MTF diagrams, and have wondered about the differences
between the 40, 20 and 10 lp/mm curves that are usually shown.  I always
consider only the 40 lp curve when trying to compare lenses, but you are
inplying that the 10 lp curve may actually be more important.  I guess what
I need (and perhaps the LUG as well), is a short tutorial on how th read
MTF diagrams, and the meaning of "microcontrast".  

Erwin, perhaps when you have some spare time, would you be up to providing
the LUG with such a tutorial?

Thanks

Dan C.