Archived posting to the Leica Users Group, 1998/05/30

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Subject: Re: [Leica] 50 f1.4/180 f2.8 apo MTFs
From: Erwin Puts <>
Date: Sat, 30 May 1998 15:35:55 +0200

You wrote

>I just got the MTF diagrams from Leica for the new R-50 f1.4
>& the 180 f2.8 apo lenses. I also have the BAS charts for
>most previous Leica glass; thus, we can get at some
I have stated it before and got screaming protests. Still this is my view:
1. BAS test results are worthless in themselves and can not be compared to
any other testresult.
2. BAS results  are NOT (repeat NOT) MTF measurements and/or evalutions.
BAS uses a  projection method: a fine transparant testchart with the usual
blocks of lines (horizontally and vertically) is projected on a wall. Then
a CCD  video camera with 430000 pixels takes a shot at 80x enlargement.
This result is fed into a computer where an unknown softwareprogram
analyses the data. How and what is analysed is not known.
3. Even if BAS were a MTF measurement: one can not compare two MTF graphs
if the  method and paramaters are not identical. As every manufacturer uses
a different program and different parameter,s any comparison is impossible
or a very dangerous undertaking. Some conclusions might be made if more is
known about the several MTF measurement programs. I do know the ones from
Zeiss and Leica quite well and so could compare the results and get some
very cautious conclusions. I would not dare to do so with Canon graphs.
4.Even if the graphs are comparable then the actual results might differ
quite well, as any one has its own set of interpreatations. As example. The
10lp/mm for the Zeiss Planar G 2/50 is situated lower on the curve than the
Summicron-M 2/50, So the Summicron should have higher contrast at full
aperture? Ask PopPHoto or Chasseurs d"Image!
5. Comparisons of lenses based on some graphs, how tempting it might be, is
a minefield. Be aware of this fact: it might be the only true conclusion
from my extended research into lens comparisons.