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How do i read the MTFdata

G

Guest

what does the lines say to me?

can i read the quality on this diagrams?

how should i do this?

thanks!
 
G

Guest

An explanation how to read and interprete the MTF data is in the second topic of the forum (overview)

dirk
 
G

Guest

Check out this link for some rules of thumb.

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ie. For a lens to be very good; " the 40 lp/mm curves: >20% for the corner (right) >65% for the center (left). the 20 lp/mm curves: >45% for the corner >80% for the center. the 10 lp/mm curves should be very close to the 5 lp/mm curve. the 5 lp/mm curves should stay >95% for the whole X-axis. "

Another rule of thumb. 5/10 lp/mm measure contrast, 20/40 lp/mm measure resolution.

BUT MTFs are not everything. There are lots of things they don't test. MTFs are usually perform with the lens set at infinity, so they dont test performace at closer distances nor macro performance. They don't measure the bokeh, and otherwise don't quantify the character of a lens.

They DO measure the sharpness and abberations of a lens from the centre of an image to the edges.

This leaves lots of room for differences of opinions. For ex&le I dissagree with almost everything that has been said about G and Y/C FFL lenses being inferior to newer zooms despite the MTFs of the zooms being very good.

I find the newer zooms don't have the Zeiss character, they might as well be Nikon or Canon

YMMV

BTW does anyone else find this forum clumsy to use, why not just a normal mailing list, thats web archived?

works for the LUG and RUG

Brian
 
G

Guest

thank you guys verry mutch!

sorry, but i'm not shure if i do understand
the article correctly :^(
my english is far away from perfect :)

do you know were i can find an similar article
on german language?

thanks
 
G

Guest

2do you know were i can find an similar article on german language?2

Contact Zeiss in Oberkochen. They might have still a copy in German. It is not available on their website. Tell them that you are coming from Contaxinfo.com

dirk
 
G

Guest

hi dirk,

not the sheets :)

i ment an article how i can read and understand
the tables!
 
G

Guest

Yes I meant the article too.

The article you find on my site in English have been also printed in German. BUT they are not on the website on Zeiss. You have to call them to get a copy.

dirk
 
G

Guest

Hi Dirk,
You mentioned that the MTF 20/40 l/mm measured the resolution. Sometimes, the resolving power of lens is much more than 40 line/mm. Is there any direct relationship between resolving power and MRF ?

Francis.
 
G

Guest

> Hi Dirk, > You mentioned that the MTF 20/40 l/mm measured the resolution. > Sometimes, the resolving power of lens is much more than 40 line/mm. > Is there any direct relationship between resolving power and MRF ?

Er I think its was me that rashly said this..

I'm not familiar with the acronym MRF, I assume you mean MTF?

In the words of Dr. J. Kämmerer from Zeiss From the secondarticle mentioned below

"In the miniature and medium-format photography which we are dealing with here, the spatial frequency range above 40 cycles/mm has virtually no influence on the image quality perceived by the viewer."

The BEST thing to do is to read

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then
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The second is an EXCELLENT article BTW

Then
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or try the schneider site

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. pdf

EVERYONE should check out the lens cleaning article on the schneider site

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In any case don't stress. Its more important to use your Zeiss lenses than to measure them.

I have made 16"x20" enlargements of shots taken with 40 year old contax rangerfinder lenses (the 50mm sonnar and 35mm biogon come to mind) that are fantastically sharp and creamy.

BTW In an earlier post I sounded a bit critical of contaxinfo, and I guess Dirk. I didn't mean to sound that way (bad day). I love the contaxinfo site, and use the information in it all the time. I guess that means I should donate. I'll have to check the wifes' credit card debt first.

Brian
 
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