rosuna Posted October 23, 2007 Share #1 Posted October 23, 2007 Advertisement (gone after registration) Leica has published a new brochure with MTF graphs: http://www.leica-camera.us/assets/file/download.php?filename=file_3234.pdf They are really good. See, for instance, the Summarit-M 75mm.... Link to post Share on other sites More sharing options...
Advertisement Posted October 23, 2007 Posted October 23, 2007 Hi rosuna, Take a look here Summarits' MTF graphs. I'm sure you'll find what you were looking for!
rosuna Posted October 23, 2007 Author Share #2 Posted October 23, 2007 This "practical experience" report is interesting too: Leica Camera AG - Photography - Summarit-M lenses Link to post Share on other sites More sharing options...
adan Posted October 23, 2007 Share #3 Posted October 23, 2007 Thanks, Ruben: Brochure does reveal the lens hoods (rectangular for 35/50, round for 75/90 - all come with rubbery caps). It may be a pdf artifact, but it looks like the 35/50 shade has a small 'step' on the back edge, perhaps as a stop to ensure alignment when it is screwed on? I think the Summarits may be on display here in Denver sometime in Mid-Nov. at a Leica Day. It will be interesting to see how those mtf graphs translate into real pictures. Going soley by the curves, they do look like they are "derated" versions of the equivalent Summicrons - dips and peaks in about the same places. Which is more or less how both E. Puts and LFI have described them. I wonder now - if there are f/3.5-f/4 18, 21 and 24 lenses on the way, in about the same price range as the Summarits, as hinted at by the LFI interview - will they be named as Super-Elmars or Elmars - or what? Link to post Share on other sites More sharing options...
rob_x2004 Posted October 23, 2007 Share #4 Posted October 23, 2007 Maybe the experienced could discuss points of interest in the charts, theoretical comparisons with others. Why some property could be interpreted or expected from the graphs. They are all just curves to me at the moment. Link to post Share on other sites More sharing options...
luigi bertolotti Posted October 23, 2007 Share #5 Posted October 23, 2007 Maybe the experienced could discuss points of interest in the charts, theoretical comparisons with others. Why some property could be interpreted or expected from the graphs. They are all just curves to me at the moment. Basically the graphs allow us to confront Summarits with other Leica lenses (Leica Co. published the MTF graphs for all of theirs, can be found in website), limited to sharpness, that is strictly related to the MTF tests; sharpness is important, but is only ONE of the factors that make the "global rendering" of a lens: lot of threads have been posted here on the OOF "quality" (sorry, I don't like the term "bokeh" ) ... many of us give it a great importance.. then there is the color balancing, a delicate factor which can be very variable for different glasses... and also the mechanical factor takes its toll...smoothness of focusing is very important on a RF... and, maybe most of all, many M8 users have suffered in someways the focusing issues on certain focals, and shall be very interesting to see if Leica has found a way to front this issue with the new Summarits... OK for the MTF graphs, we can trust Leica data... but wait for some complete and indipendent review. Link to post Share on other sites More sharing options...
rob_x2004 Posted October 23, 2007 Share #6 Posted October 23, 2007 Luigi, bokeh is a Japanese porn term I think. Anyway, I am sure that the start points gradients turns and inflections in the curves tell something in the comparisons otherwise they wouldnt bother plotting them. Other factors obviously come into play, but if curves are published it would be handy to understand them. Link to post Share on other sites More sharing options...
rosuna Posted October 23, 2007 Author Share #7 Posted October 23, 2007 Advertisement (gone after registration) You can also infer many things about bokeh from the MTF graphs. Anyway, in terms of sharpness, you have more than 50% of contrast for 40 lp/mm wide-open for all lenses at the center of the frame, with a very uniform rendition in the borders and corners. In particular, the 75mm Summarit is impressive. The performance at f/5.6 is outstanding for all lenses. Very good. These Summarits aren't "poor" M lenses. They are just as powerful as the best Summicrons are, but giving 2/3 stops. Link to post Share on other sites More sharing options...
adan Posted October 23, 2007 Share #8 Posted October 23, 2007 Rob: I guess you know the basics of MTF charts, but just in case... They graph contrast on the vertical axis vs. distance out from the center of the image on the horizontal axis ("image height") . At different resolutions (usually 5, 10, 20 and 40 lppm). And for two different line orientations: a radial line out from the center, and a tangential line, which would be at 90 degrees to the radial line. The more all the lines are grouped towards the top of the graph, the more contrast the lens has overall. If the upper lines are very high, but the lowest set is pretty low, the lens is contrasty but not especially sharp. If the 4 line sets are tightly grouped, then the resolution is usually high, and the contrast can be judged by how high the grouping is on the graph. If the lines curve down significantly on the right side, the corners will likely be noticeably fuzzier. If the lines run fairly level all the way across, the lens has very even performance all the way to the corners (an impressive achievement if it occurs at full aperture!) If the dotted and solid lines diverge significantly, that usually means there will be a bit of streaking to the image - details will be slightly blurrier in one direction than in the other, as though a finger had smudged them. Personally, I find the standard MTF charts to be flawed in two ways. They mix together contrast and resolution, such that a contrasty but not especially high-resolving lens can have just as high a chart as a sharper but less contrasty lens. And they ignore results beyond 40 lines per mm, which frankly is a pretty low resolution by modern standards. (Back when Pop Photo actually measured resolution in their tests, in the 60's, 40 lppm only earned an "acceptable" rating). In effect, MTFs measure "apparent sharpness" - what will look sharp and snappy in a small-to-medium sized print from a low-acutance medium such as color neg films (especially those that were prevalent back when Canon first began using MTF as a marketing tool in the early 70's). Zeiss and others did studies that showed than for most consumers, a high MTF - good contrast down through 40 lppm - was all a lens had to produce to "look good". I just have a different standard for performance. But even so, MTFs can provide some guidance. Link to post Share on other sites More sharing options...
rosuna Posted October 23, 2007 Author Share #9 Posted October 23, 2007 You are right. From a 35mm negative to a A4 print you need an enlargement factor of 8. Then, 40 lp/mm translate to 5 lp/mm on paper (the sensor has something to say, but lets me simplify a bit). This is the maximum detail you can see at optimum distance. In the digital era, most people make prints at A3 sizes, and 40 lp/mm would lead to 2,5 lp/mm of real detail on print, and that is much. Therefore, the 40 lp/mm is a good point of reference for larger prints, which need more distance of observation anyway. Even more, people now use to see images on computer screens. At 96 ppp (normal screen density) a 10MP image at 100% is like seeing a print of 170x100 cm! For screen pixel peeping the 40 lp/mm isn't enough, but you shouldn't care too much about screen inspection. A 24x36mm full frame sensor with 80 lp/mm lead us to 22,2 MP. The Nyquist theorem asks for double of the sampling frequency than signal frequency for a clean reproduction of the signal (if they are in phase, etc.). This is simplification too, but a sensor with 80 lp/mm of sampling frequency is able to reproduce accurately just 40 lp/mm (Bayer mosaic, anti-alias filter, the nature of the photographic signal, etc. ask for many simplifiying assumptions here, but you get the idea). The MTF curves are really, really good. The new Summarits are just as I expected: as good performers as the Summicrons are. The price is much lower, you give 2/3 stops, but the performance is superb and the built quality is 100% Leica. Link to post Share on other sites More sharing options...
luigi bertolotti Posted October 23, 2007 Share #10 Posted October 23, 2007 Andy & Bob... well written, compliments to both: synthetic and clear explanations ; I already thought at the 75... a focal I haven't; it IS mine:) . And... I'll wait for some review on the 35... Link to post Share on other sites More sharing options...
Shac Posted October 23, 2007 Share #11 Posted October 23, 2007 Andy-Ruben - as a newcommer to this forum - thank you both - I think I am finally beginning to understand MTF's. Your explanations are clear and much appreciated. David Link to post Share on other sites More sharing options...
tom0511 Posted October 23, 2007 Share #12 Posted October 23, 2007 This "practical experience" report is interesting too: Leica Camera AG - Photography - Summarit-M lenses Mmmhh, I dont know. He loves the 35/1.4asph but then he says in the end that he would probably get a 35/2.5 because of lower price if he had to do it again. Actually I can not find anything interesting in this article Link to post Share on other sites More sharing options...
sean_reid Posted October 23, 2007 Share #13 Posted October 23, 2007 This "practical experience" report is interesting too: Leica Camera AG - Photography - Summarit-M lenses I like Rainer and enjoyed meeting with him when he was (recently) the head of the M camera division at Leica. Cheers, Sean Link to post Share on other sites More sharing options...
rob_x2004 Posted October 23, 2007 Share #14 Posted October 23, 2007 Rob: I guess you know the basics of MTF charts. Yea right. Thats why I have been googling like mad. Thanks for taking the time to respond. By next week I shouldnt be so dense. Link to post Share on other sites More sharing options...
luigi bertolotti Posted October 24, 2007 Share #15 Posted October 24, 2007 Andy & Bob... well written, compliments to both: synthetic and clear explanations ; I already thought at the 75... a focal I haven't; it IS mine:) . And... I'll wait for some review on the 35... ...sorry Ruben... my "Bob" was referred to you... don't know how I mistaked... Link to post Share on other sites More sharing options...
Confusion Circle Posted October 24, 2007 Share #16 Posted October 24, 2007 Luigi, bokeh is a Japanese porn term I think. LMFAO. "Bokeh" is a Japanese word meaning "unclear." It can be used in a broad way. For instance, it can mean forgetfulness in a person, the OoF qualities in a photo, fog, etc. Link to post Share on other sites More sharing options...
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