Archived posting to the Leica Users Group, 1999/04/20

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Subject: [Leica] resolution versus contrast?
From: Erwin Puts <>
Date: Tue, 20 Apr 1999 19:44:17 +0200

DonjR43198 wrote:
>The move from placing greatest emphasis on resolution to placing more
>emphasis on contrast and reducing resolution to achieve that goal was pointed
>out in some of the Leica literature in the early 60's when Leica began to
>market the lower resolution 50 mm Summicrons.  The brochures actually
>illustrated this with side-by-side comparisons showing that the eye perceived
>high contrast but lower resolution as the sharpest image.

>It would be very nice if Mr. Puts would undertake to compare the resolution
>of the old D-R Summicron with the present day Summicron.  The ones I have
>tested show the D-R Summicron sporting a center resolution of 112-120 lpm to
>about 80-88 lpm for the current Summicron lenses.  Further, the studies I
>have seen from the laboratory of Mr. Puts are conducted using color film
>rather than Tech Pan or a microfilm.

>If the current Summicrons really outperformed the D-R for resolution, I would
>have one on my M cameras but there have been no "figures" published, at least
>that I could find, that show the current Summicrons will resolve even 100
>lpm.  Maybe this discussion will result in such figures being located or
>determined or at least generate some discussion.

>Should you have some "figures" rather than subjective comments from various
>testing organizations, I would very much like to see them.

There are several topics here. In the past there was indeed a balancing of
resolution versus contrast. The state of aberration correction in general
is such that there does not exist one sharpness plane of best focus, but
many. Every focus plane gives a different size of the spotdiagram and
therefore a different recording of a point. By shifting the focus plane one
could give more emphasis on resolution (smaller spot size, but more
diffusion around it) or contrast (bigger spot size but sharp edges).
Recently the designs have evolved to a situation where resolution AND
contrast are both at the same time feasible. Naturally modern Leica lenses
exhibit this trend.
I did analyse the resolution the resolution of the DR and the current
Sumicron as I said in my comparison report. I refuse to give figures
because they are irrelevant for a serious assessment of image quality and
would only revive the older and obsolete discussions.
I wonder which studies from the "laboratory of Mr Puts" you have seen to
warrant the conclusion that I use color film rather than TP or microfilm.
To be sure the current Summicron will outperform the DR in all aspects
including resolution.