Variables of MTF lens testing

[Mustafa Umut Sarac]

Variables of MTF Test

I bought a 1954 FED1 with an Lens 4871 Serial number Coated 50mm f:3.5 FED , an Elmar 5cms f:3.5 Copy.

I want to test the lens MTF.

I found from internet 48x31 cms Resolution Chart which prepared to ISO Standarts.

I will order an printout next week from a printer which has a large selection of big industrial printers . I will take pictures of chart for each aperture and order a HR 17MB Tiff Scans and test the big H printouts at the chart with MTF Extraction Software.

But

Printer resolution
Scanner resolution are the two things to itch me.

Do they effect the MTF test and what is the way to overcome this problem without sending the lens to Zeiss option

Umut

 

[ic-racer]

How about using the chart mentioned in this website and a high power loupe and estimate the MTF yourself as demonstrated.
http://www.normankoren.com/Tutorials/MTF5.html#Distance

 

[ic-racer]

If you want to scan, here are some guidelines from that site:

Scan the film image. Observe it on your computer and analyze it using ImageJ or PixelProfile. Works well with 4000 dpi scanners and digital cameras but doesn't quite cut it for measuring lens resolution with 2400 dpi scanners. If you print digitally this technique has the advantage that it accurately represents your imaging system. Using the |sinc|3 approximation for a properly functioning film scanner, the 50% MTF frequency (f50) is about 0.366*dpi (or dpmm), and the 10% MTF frequency (f10) is 0.629*dpi. For a 2400 dpi (94.5 dpmm) scanner, f50 = 34.6 lp/mm and f10 = 59.4 lp/mm. Not impressive. For a 4000 dpi (157.5 dpmm) scanner, f50 = 57.6 lp/mm and f10 = 99 lp/mm. This is good enough to distinguish between good and excellent lenses, but I'd want more if I could get it. Sharpening boosts a scanner's f50 and f10, but it can confuse the results if you don't apply it with consistency.

 

[E. von Hoegh]

I posted this today at another site. This is the only meaningful test I have devised for my lenses:
"My criterion for judging the sharpness of a lens is to make one negative, focussed at infinity on something with a good deal of fine detail. It could be tree limbs, bicycle wheels, signs, almost anything. Then I look at the negative with a dissecting microscope. If it renders the fine detail, it's sharp for my purposes, since few hang photos of test charts on their walls."

This isn't the best way to arrive at a quantitative comparison, though.

 

[Mustafa Umut Sarac]

My criterion for a lens to get anatomical detail from the portraits or few meters faraway human subjects. Skin details , muscles like an Greek sculpture drapery and below the skin the blood flow. For that color saturation , I test the subjects under oldest technology light bulbs at night. I must see the clean red blood flow and green blood flow. I only get this result from Leica lenses , especially Summitar. And my Rollei 35S with Sonnar 40 have a similar nature.

When it comes to scanning and dpi thing , I hate that stuff. I dont think their printers are not well calibrated and free charts would print bad. Buying a chart is more expensive than original Leica .

 

[Dan Fromm]

Ok, since I've already responded nastily to one !@$ today I'll do it again.

Mustafa, what does MTF have to do with what you want the lens to do for you? Why screw around with trying to measure MTF when you can simply take a few shots and know whether the lens will do what you want it to? And why do you think a Soviet-made imitation Elmar will do what a Summitar does? Why not just use your Summitar and get on with your work?

I've said it once today, I'll say it again. There are too many damfools here.

 

[E76]

I wouldn't try to measure MTF with some kind of chart you found on the internet and printed out—too many variables in the process to allow for a measurement of any accuracy. I would suggest you purchase an ISO-12233 chart or similar and use slant edge MTF (although this will require that you digitize the image).

That being said, I completely agree with Dan. Why the do you need to know the lens MTF anyway?

 

[Poisson Du Jour]

MTF curves are irrelevant in practical photography. Sure, you learn about these in art school with photography major, but other than that, pffft. The real thing to concentrate on is quality of your work, knowledge of your subject, an holistic and consistent approach to presentation and disregard for distractions that serve no useful purpose other than to get you hot and bothered when that is not what photography is about.

 

[Diapositivo]

Have you tried http://www.quickmtf.com/ ?

The idea of measuring MTF by shooting charts is somehow flawed at its root. A proper MTF test should be performed on an optical bench.

http://toothwalker.org/optics/lenstest.html

I've read somewhere that MTF tests are heavily influenced by the quality of lights, so that proper results are obtained by a properly equipped laboratory, and results are not even constant between laboratories for light quality problems.

You don't need to send the lenses to Zeiss, any laboratory equipped for this kind of tests will do, they should be a bit everywhere, this is 1940 technology after all. I have no idea of how much this would cost.

 

[E. von Hoegh]

MTF curves are irrelevant in practical photography. Sure, you learn about these in art school with photography major, but other than that, pffft. The real thing to concentrate on is quality of your work, knowledge of your subject, an holistic and consistent approach to presentation and disregard for distractions that serve no useful purpose other than to get you hot and bothered when that is not what photography is about.

You're correct. I think the OP wants a quantifiable way of comparing two lenses, which is fair enough.
But, comparing MTF reminds me of the audiophools, who sit around comparing unquantifiable qualities to the extent of forgetting that the gear was meant as a way to hear music.

 

[eclarke]

Yeah, way too much thinkig..

You're correct. I think the OP wants a quantifiable way of comparing two lenses, which is fair enough.
But, comparing MTF reminds me of the audiophools, who sit around comparing unquantifiable qualities to the extent of forgetting that the gear was meant as a way to hear music.

 

[Prof_Pixel]

The idea of measuring MTF by shooting charts is somehow flawed at its root.

What you will end up with is the cascaded lens and film MTFs.

 

[Dan Fromm]

Folks, read post #5 in this thread. In it the OP explained what he really wants to accomplish.

I've been on the fence about the OP for years. On the one hand, he often seems completely insane and his recent posts have been more incoherent than usual. On the other, he isn't a native speaker of English; given how hard it is for native speakers of English to express themselves clearly in their own language, I can only respect him for making the effort and trying to communicate with us in ours.

This thread is a lovely example of one of the reasons why I denigrate bulletin boards. Posters, after the first couple, have responded either to the OP's original post and ignored his second (and so far latest) post, #5, or they're responded to a post after #5. The entire thread, with the exception of the original poster's two posts and one other, is completely off-target and is getting farther from what I think the OP wants to learn. Its appalling.

 

[Prof_Pixel]

The OP (in his first posting) brought up the subject of MTF. Even the subject line of this thread mentions MTF.

 

[Diapositivo]

The OP asked a question about how to perform some MTF tests to a FED lens he has and how the admittedly imperfect method he would use would affect the results.

He received answers stating that MTF tests are useless and a user inferred the OP thinks the FED lens was superior to his Leica (which the OP never stated).

A discussion about MTF or resolution tests and their relative scarce utility in measuring the quality of a lens would be a welcome discussion but in this thread is OT just like a comparison between Leica and FED lens could be interesting but OT.

Dan is right that, for the most, this forum ignored the OP question and just begun questioning his motives to ask it, which just lowers the noise/signal ratio. This post does not raise it either but can be taken as a remainder to be more disciplined in forum behaviour oliceman:

 

[Dan Fromm]

Oh, my. I spent most of my career working as a consultant. Consultant in the old sense of outside expert, no in the modern sense of contract laborer who needs close supervision. It sometimes looked as though I spent most of my time on data processing, applied statistics, computer science, but all that was in the interest of solving clients' problems. I like to think that I wasn't quite the worst that ever was.

In the earliest stages of a project a good consultant hears the client out and probes to find out what the client actually wants to accomplish. The real problem, or what the client wants to accomplish, often has little to do with the problem as initially presented. Fixating on the problem as originally presented can lead to disaster. I've seen it happen.

The OP started this discussion by asking a question about something he wanted to do. In post #5 he explained why. His goal, as revealed in post #5, is to find out whether his new treasure will take a particular kind of picture. Answering this question has nothing to do with what he first said he wanted to do. More evidence of unclear thinking.

Prof_Pixel, if you'd worked for me and consistently been as inflexible as you were in post #14 in this thread I'd have fired you.