Would someone explain MTF charts

[ron_9]

I'm sorry, even after reading the explaination I still didn't understand what it was trying to say.. S10, M10,S30,M30 what are they, what's the dash line verus solid. gheez I can look at photzone and make some since out of it--but these make no since. I'm guessing a straight line across the top with both dshed and solid line would be a good thing--but I'm not sure--point me in right direction---ron s.
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Keeping it sane in an insane world is an inconvenience at an inconvenient time!!
http://www.pbase.com/ron9ron

 

[rgmoore]

MTF charts are less complicated than everyone makes them out to be. The different lines represent how much detail the lens is able to record at different scales. The M10 and S10 roughly correspond to what we think of as contrast, while the M30 and S30 roughly correspond to what we think of as sharpness. The height of a line represents how well the camera is recording that kind of detail; the higher the better. The horizontal distance represents how far from the center of the lens they're measuring, with the center at the left and the extreme corners at the right.

Obviously, the ideal lens would have the lines going straight across and all the way up at the top. In practice, the 10 line is always higher than the 30 line, and it's frequently a fair bit higher. That just means that the lens can resolve coarse detail better than fine detail. The lines also tend to sag toward the right side of the chart, showing that the corners are softer than the center. The key thing to look for there is how quickly they sag. If they stay mostly straight and only drop off at the very far right side, that good contrast and sharpness will extend over most of the picture. If they angle down more uniformly across the chart, only the center will be really great, with performance declining steadily across the frame.

The only complicated part is the distinction between the S and M lines. The S line represents the ability of the lens to resolve radial lines, while the M lines represent the ability of the lens to resolve circumferential lines. The distinction isn't vital if you're only looking at the charts casually; in that case you only want to look to make sure that the two lines stay close together. If one is much lower than the other, it's a good bet that the lens suffers from some poorly corrected aberration.
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As with all creative work, the craft must be adequate for the demands of expression. I am disturbed when I find craft relegated to inferior consideration; I believe that the euphoric involvement with subject or self is not sufficient to justify the making and display of photographic images. --Ansel Adams

 

[Yidahoo]

They are a series of charts designed to show people who never take photos, how sharp their lenses are!
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http://www.jasonrow.wordpress.com
'Travel is the antidote to racism, bigotry and prejudice' Mark Twain

 

[Les Olson]

I don't know if this is what you had in mind, but these are superb. They need a bit of effort, but that is the way it is:

http://www.zeiss.de/C12567A8003B8B6F/EmbedTitelIntern/CLN_30_MTF_en/ $File/CLN_MTF_Kurven_EN.pdf and

http://www.zeiss.de/C12567A8003B8B6F/EmbedTitelIntern/CLN_31_MTF_en/ $File/CLN_MTF_Kurven_2_en.pdf.

http://www.microscopyu.com/articles/optics/mtfintro.html (this site has many other outstanding articles, though you probably need some technical background).
--
2 November 1975.

'... Ma come io possiedo la storia,
essa mi possiede; ne sono illuminato:
ma a che serve la luce?'

 

[ron_9]

In the spirit of your little tag, they also help "people" who do take images to evauluate a possible new lens and focal group, while looking at overall IQ, CA, vignetting, etc.. Of course the story is what comes up on one's own screen, but we have a lot of chocices and so little time.

I just know you weren't directing your cynicism at me, but if you are--"come here fella, and let me give ya a little hug" ---ron s.
p.s. thanks for the common english answer guys, makes a bit more sense

They are a series of charts designed to show people who never take
photos, how sharp their lenses are!
--
http://www.jasonrow.co.uk
http://www.jasonrow.wordpress.com
'Travel is the antidote to racism, bigotry and prejudice' Mark Twain

--
Keeping it sane in an insane world is an inconvenience at an inconvenient time!!
http://www.pbase.com/ron9ron

 

[anotherMike]

Three quick comments before I head on out the door...

a) The first reply to your post is the best simple answer

b) The post with the guy recommending the Zeiss MTF documents is absolutely a must read

c) Don't read the manufacturers MTF curves as being completely correct - as Dr. Caldwell (designer of the Coastal Optics 60) pointed out in a thread here some time back, even a perfectly designed lens could not have a 99-100% contrast rating (the 10 lp/mm line) in reality - I forgot the figure he used which was the max, but it means that some manufacturers are using theoretical MTF, not MTF measured from the lens itself. Zeiss and Leica will give you measured MTF though, but Nikon/Canon don't. Not that you can't take a look and gain some idea of the performance for some things, but..... (and also remember the manufacturers graphs are with the lens shot wide open, which is a bit less useful IMO)

d) MTF charts are useful, but don't tell everything. Remember that real life is three dimensional, shot in varying light sources, at varying distances. MTF charts are shot at one distance, in one light type, and are two dimensioanl. In my own experience (and I'm one who has done "scientific" lens testing way back in the day), there are times that a lens that maybe doesn't look quite as good on the MTF test chart ends up offering much better image quality in real life than the lens with the better graph. Use them as just one data point in your research, nothing more. They most certainly are not "bragging proof" that one lens is absolutely better than another.

-m

 

[Duckie]

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Bravo! This is great!