lct Posted June 24, 2018 Share #21 Posted June 24, 2018 Advertisement (gone after registration) Been using lens charts for 30+ years. Not sure they were true MTF charts then but i've always used those charts as a simple way of checking main strengths and foibles of lenses so i don't quite understand what throwing them in the bin may bring to photographers. Quote Link to post Share on other sites More sharing options...
Advertisement Posted June 24, 2018 Posted June 24, 2018 Hi lct, Take a look here Throw the MTF charts into the bin!. I'm sure you'll find what you were looking for!
UliWer Posted June 24, 2018 Share #22 Posted June 24, 2018 YES! Summar 5 cm. A masterpiece from the thirties. [/url] Well, if you look at the MTF for the Summar - published in the Leica Pocket Book 8th edition p.163 - the Summar in the center is not far behind the current Summicron. Towards the edges the Summar drops dramatically, which is a feature that makes the lens interesting. You may even see the character of the lens on your photo: the left eye being considerably more sharp than the right one, the edges - which are unimportant for your photo - showing just unsharp blur. No novelty; there are many good photos with „bad“ old lenses in the thread „The view through old glass“. 1 Quote Link to post Share on other sites More sharing options...
pgk Posted June 24, 2018 Share #23 Posted June 24, 2018 If you read up on the charts supplied by lens manufacturers you will probably find that many are theoretical - that is they are the design MTF predictions because clearly lenses will vary (within tolerances). So they help the lens designers work out how effectively a lens will meet its design intentions. Tested lenses will probably vary from these but should be within a relevant tolerance. MTF charts are as useful as their users want them to be - understand what they are showing and combine this with other useful information and they can be very helpful. I would repeat though that they need to be used 'intelligently' - that is they need to be interpreted with other data to give a rounded view of how useful a lens will actually be for its application. I'm not going to go into whether those who understand MTF data can or can't be artistic but I personally know photographers who understand MTF data in intricate detail and are also capable of excellent photography. 2 Quote Link to post Share on other sites More sharing options...
Jeff S Posted June 24, 2018 Share #24 Posted June 24, 2018 Roger Cicala from Lens Rentals has written some articles on understanding MTF. He wants readers to be able to at least gain a basic understanding when following his blog. But unlike many geeky reviewers and testers, he always puts any technical findings into a broader context so that one can understand his gear reviews and comparisons on a very practical level. He has been known to debunk some internet mytths, plus he’s a good, and funny, writer. https://www.lensrentals.com/blog/2014/05/mtf-the-english-translation/ Jeff 1 Quote Link to post Share on other sites More sharing options...
steamboat Posted June 25, 2018 Share #25 Posted June 25, 2018 If an MTF chart walked in and sat next to me I wouldn't know what it is. No idea. All of you carry on and good luck with your photography. :-) Quote Link to post Share on other sites More sharing options...
Jeff S Posted June 25, 2018 Share #26 Posted June 25, 2018 Michael Reichmann (R.I.P.) wrote a nice summary of MTF and why it should matter to some, especially those who like to talk about lens ‘sharpness’ or resolution or contrast.... and don’t know the difference.... https://luminous-landscape.com/mtf/ Jeff 2 Quote Link to post Share on other sites More sharing options...
pgk Posted June 25, 2018 Share #27 Posted June 25, 2018 Advertisement (gone after registration) Oddly enough I bought a new lens recently - a cheapish Canon 10~18 for use on a 60D/A7II. I haven't seen an MTF chart for this lens but I can assure everyone that its principle requirements were for excellent close-focus ability and fast focus. It has these two attributes but I can assure anyone that its also a great performing lens - it delivers technically sound images in the application to which its being put. That said my use is underwater behind a compact dome which is less than ideal - for survey work - and MTF charts of its use in this situation don't exist. As I said MTF is useful if available and when interpreted properly ..... Quote Link to post Share on other sites More sharing options...
pico Posted June 25, 2018 Share #28 Posted June 25, 2018 If an MTF chart walked in and sat next to me I wouldn't know what it is. No idea. All of you carry on and good luck with your photography. :-) My old workshop had a wiring chart for an MTF (DB9 Male to DB25 Female) adapter. Doesn't help, does it. Quote Link to post Share on other sites More sharing options...
Fgcm Posted June 25, 2018 Author Share #29 Posted June 25, 2018 Michael Reichmann (R.I.P.) wrote a nice summary of MTF and why it should matter to some, especially those who like to talk about lens ‘sharpness’ or resolution or contrast.... and don’t know the difference.... https://luminous-landscape.com/mtf/ Jeff Ciao Jeff, thanks for suggesting LL. Some years ago, H.H. Nasse, one of the foremost experts in optics at Zeiss, published two very comprehensive articles on the interpretation of MTF curves. You can download both papers here: https://lenspire.zeiss.com/photo/app/uploads/2018/04/CLN_MTF_Kurven_2_en.pdf https://diglloyd.com/articles/ZeissPDF/ZeissWhitePapers/Zeiss-HowToreadMTFCurves.pdf Nasse writes for the educated reader. He gives many concepts, never asking the reader to go into complex maths. Franco 2 Quote Link to post Share on other sites More sharing options...
Fgcm Posted June 25, 2018 Author Share #30 Posted June 25, 2018 This another source of very interesting papers published by Zeiss https://lenspire.zeiss.com/photo/en/article/overview-of-zeiss-camera-lenses-technical-articles/ 2 Quote Link to post Share on other sites More sharing options...
adan Posted June 25, 2018 Share #31 Posted June 25, 2018 My take: 1. I understand MTF charts to some degree. My pictures are interesting enough to sell in the gallery, and gather some national photojournalism awards. Snide comments to the contrary. About the only thing I can't "visualize" perfectly from MTF charts is what an extreme split between the solid and dotted lines mean - coma? astigmatism? I can kinda-sorta see something in actual pictures sometimes, but not consistently. It's not that hard to see the MTF lines take a dive on the right side, and see the corresponding softness in the corners of the pictures. And that, stopped down to f/8, improvement in the MTF also shows up in the pictures as clearer corner details. It is pretty easy to see in real pictures that my 75 Summarit really is sharper @ f/2.4 than my 50mm Summicron @ f/2 or f/2.8, (with similar framing) - as the MTF charts indicate. 2. "Understanding" and "paying much attention to" are two different things. I started in photography just barely before MTF charts entered the public consciousness (the first ones I saw were in Canon's ads introducing the new F-1 and FD lens line about 1971 - "What the heck are these!?"). Most of the lens data I saw in magazine reviews for a few years after that were still separate tables of raw resolution and raw contrast: "f/2.0 - center of the image - 55 lpmm - contrast 50%, corners, 30 lpmm, contrast 20% f/2.8 - center of the image - 62 lpmm - contrast 55%; corners, 45 lpmm, contrast 28% . . f/8 - center of image - 80 lpmm - contrast 72%; corners, 65lpmm, contrast 60%..." etc. MTF charts combine resolution and contrast into a single graphable number, and ignore the raw resolutions I care about (if and when I care about resolution). But high macro-contrast (good lens coatings; using a minimal number of elements) can "rig" an MTF test higher without actually increasing resolution. I prefer a lens that can resolve 80 lpmm with, say, 25% contrast to a lens that resolves only 50 lppm but at 60% contrast (but the second will likely graph better on an MTF chart, which rarely measure lenses at resolutions more than 40 lppm). Especially now with digital image processing, since lens edge contrast (but not resolution) is exactly what a digital "sharpening filter" improves anyway. I want the "80 pickets in the fence per mm" to be recorded by the lens (when needed) - I can increase their contrast myself. 3. I mostly use lenses with "lesser" MTF quality (to the extent I can even find MTF charts for them - 1980 or earlier-designed 21/28/35/135) because I like something else they do (Mandler-era lower macro-contrast (read: avoidance of blown highlights or blocked shadows) and color palette). As the OP says, MTFs are not everything. So while an MTF chart can provide some guidance, I shoot a lens myself rather than buy simply based on the MTF charting. I do in fact keep some of Leica's .pdf lens brochures with MTF charts around on my computer. They are informative (especially if someone here on the forums asks "Why are my 35 f/1.4 ASPH pictures so fuzzy in the corners - is that normal?!"), but they are not definitive. 1 Quote Link to post Share on other sites More sharing options...
pico Posted June 25, 2018 Share #32 Posted June 25, 2018 (edited) MTF is apparently useful to some of our brighter photographers, such as adan. I am not so bright and I look to their work to find a rationale to change types of lenses. So far in thirty years my naeviety prevails. I hope my peers look more to the picture rather than lens metrics unless they are reconnaissance nuts. Edited June 25, 2018 by pico 1 Quote Link to post Share on other sites More sharing options...
Bill W Posted June 25, 2018 Share #33 Posted June 25, 2018 MTF is apparently useful to some of our brighter photographers, such as adan. I am not so bright and I look to their work to find a rationale to change types of lenses. So far in thirty years my naeviety prevails. I hope my peers look more to the picture rather than lens metrics unless they are reconnaissance nuts. I must wholeheartedly concur. 3 Quote Link to post Share on other sites More sharing options...
Jeff S Posted June 25, 2018 Share #34 Posted June 25, 2018 (edited) I enjoy reading and learning about MTF and other technical gear information, at least from writers like the two I linked above. But using MTF to decide on a lens for purchase or to evaluate a photo or print? Never have and never will. I like that photography can engage me on many different levels. Jeff Edited June 25, 2018 by Jeff S 3 Quote Link to post Share on other sites More sharing options...
Ko.Fe. Posted June 26, 2018 Share #35 Posted June 26, 2018 (edited) Michael Reichmann (R.I.P.) wrote a nice summary of MTF and why it should matter to some, especially those who like to talk about lens ‘sharpness’ or resolution or contrast.... and don’t know the difference.... https://luminous-landscape.com/mtf/ Jeff It was great! I read and understand it. Bookmarked it, because I'll forget it all in few minutes... Edited June 26, 2018 by Ko.Fe. Quote Link to post Share on other sites More sharing options...
Stein K S Posted June 26, 2018 Share #36 Posted June 26, 2018 MTF curves to me add just another (well qualified!) performance input to lenses. If that is a problem; ignore them (which I myself in practice by the end of the day often do when choosing my lenses). Attempts to totally disregard MTF curve info is to me in best case wrong... From a happy amateur probably not being able to fully interpret all aspects of MTF curves... and probably not having taken many too photos being of interest to all readers of this forum. Happy though... and still looking into MTF curves from time to time ,-) Quote Link to post Share on other sites More sharing options...
jmahto Posted June 27, 2018 Share #37 Posted June 27, 2018 (edited) Sample variation. I need MTF chart for “my lens”, else it is of only theoretical interest to me. My 40summicron-c is sharper in the center than my 50luxasph at 5.6. I don’t care what respective MTF says. Edited June 27, 2018 by jmahto 1 Quote Link to post Share on other sites More sharing options...
Jeff S Posted June 30, 2018 Share #38 Posted June 30, 2018 (edited) Roger is at it again. This is for the geeks who want to understand his new lens testing procedures that go beyond ‘standard’ MTF, with reasons why... https://www.lensrentals.com/blog/2018/06/developing-a-rapid-mtf-test-for-photo-and-video-lenses/ Jeff Edited June 30, 2018 by Jeff S 3 Quote Link to post Share on other sites More sharing options...
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