[Leica] MTF graphs again

[Erwin Puts <imxputs@knoware.nl>]

Dominique wrote in part:
>I wrote "partially" because, on the axis the tri- gives nearly 72  % and the
>summicron 68 %. The difference is lowest. But if we go far from the axis 0,
>we see that the contrast of the tri- in saggital structures is constant up
>to 6 mm, then it diminishes continually.At 15 mm we have 58 % (saggital) and
>49 %(tangential) only. For the summicron we see a growing chart with some
>astigmatism (as you observed) but, at 15 mm from the axis, we have 58 %
>(saggital) and 85 % (tangential).
>Look : 49 % v.85 % !.
>And the MTF-test made by Leica is very favourable to the tri- ! At 5.6 the
>tri is at its best. If we could compare at f4 the tri- and the summicron,
>the victory would be total for the summicron.

Dominique I am really sorry to disagree with you. We are looking at 
the same graphs as I agree with you that the 40lp/mm figures for the 
TE are indeed 72% on axis, but the asph has 58%, NOT 68%!!.The TE 
goes up slightly to 74% at 6 to 9 mm image height and becomes 58 and 
49% as you note, If I look at the same 40lp/mm chart for the asph I 
see at 15mm image height around 60%,  so very close to the TE 
figures. Your figures of 85% at 15mm image height are for the 
20lp/mm!!!!  That is you are comparing the 40lp/mm of the TE with the 
20lp/mm for the asph, So this has nothing to do with how to "extract
true facts from raw data" but simply with a careful analysis of the 
same graphs. You just want so badly the TE to be worse than the asph 
that you simply look at the wrong lines in the graph to prove your 
point.
But even if your quotes  were right you note that the TE has "58 % 
(saggital) and
49 %(tangential) only" and the asph has "58 % (saggital) and 85 % 
(tangential)". I see that saggitally the figures you refer to are the 
same, the only difference is the tangential value. Would you be so 
kind as to enlighten me why the difference in tangential MTF is so 
important and why a figure of 49% tangential is bad.


Erwin