Re: [Leica] MTF graphs again

["dominique pellissier" <noct@club-internet.fr>]

- ----- Original Message -----
From: Erwin Puts <imxputs@knoware.nl>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Sunday, February 20, 2000 12:54 AM
Subject: [Leica] MTF graphs again


> 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


########
Erwin,

I have the charts in front of me and, without hezitation, I see that the
2/35 asph at 5.6 for 40 lp/mm has nearly 68 % on the 0 axis and not 58 % as
you wrote.
2 persons agree with me.
The vertical axis has a graduation from 0 to 100 % with intervals of 20 :
0,20,40,60,80,100.
Between each graduation, you have,e.g. 70 between 60 and 80.
And the curve begins on the vertical axis near 70.
For the 40 pl/mm I've checked and i did not made a mistake.
Are the same curves we observe ?
I've checked again on the Leica site. Maybe you have other curves directly
from
leica ?


Dominique