adan Posted March 3, 2011 Share #21 Posted March 3, 2011 Advertisement (gone after registration) Let's be clear that there are actually three "focal lengths" for any lens. 1. The nominal focal length, usually rounded off to some standard such as 24, 28, 35, or 85mm and engraved on the lens in BIG type. Note the "usually," since there are always oddball focal lengths (why do Zeiss and Cosina make 25s and Leica, Nikon and Canon make 24s? Why 100mm from Canon and 105mm from Nikon? Zeiss Jena and Pentacon used to sell a 29mm.) 2. The design focal length, which is the actual targeted focal length (52mm in the case of most of Leica's "50s", as Lars notes) in the optical design process. From Leica's own spec sheets, the design FL for some M lenses: 24 Elmarit ASPH - 24.4mm 28 Elmarit ASPH - 28.4mm 35 Summilux (new) ASPH - 35.6mm 50 Nocti f/0.95 - 52.3mm 90 Summarit - 91.0mm 90 Summicron APO/ASPH - 90.9mm 90 Macro-Elmar - 90.0mm 3. The real focal length, which is subject to some variation for each individual lens built. I think there are something like 5 different flavors of 50 Summicron (even among those of the same type): 51.2, 51.4, 52.2, etc. On an SLR, the exact focal length to the 10th of a mm is not critical, since we (or the AF system) are/is looking at the actual image to determine focus. If it looks sharp, it looks sharp - whether it is an 85.5mm or an 84.9mm. On a rangefinder, however, the focus is determined by proxy, and if the focus cam does not precisely match the real focal length, there will be focus problems. So Leica labels the long lenses individually (more for use by service techs than for consumer use) - the short lenses generally have enough DoF to make the exact focal length moot. Link to post Share on other sites More sharing options...
Advertisement Posted March 3, 2011 Posted March 3, 2011 Hi adan, Take a look here Marking on Summilux 50. I'm sure you'll find what you were looking for!
EJohnE Posted March 3, 2011 Share #22 Posted March 3, 2011 Just for curiosity, could the "50" actually be "05", as the 5 looks the same whichever way up? John. Link to post Share on other sites More sharing options...
01af Posted March 3, 2011 Share #23 Posted March 3, 2011 My 75 mm Summilux has '00' engraved just to the right of the distance scale (perpendicular to the scale lettering). Serial # 31511xx. So, does that mean it is a 70 mm? (I'd be surprised.) Most likely you just didn't read that little number correctly. Have a closer look! If the 50 is mm ... It's tenths of millimeters. ... I don't follow this meaning that the lens is 75 mm. If that were the case, wouldn't it be 00? No. The correction value isn't to be added to the nominal value; instead it replaces the last digit of the nominal value. For example, if your 75 mm lens' actual focal length was 74.8 mm then the little digits would read '48'. Link to post Share on other sites More sharing options...
Xmas Posted March 3, 2011 Share #24 Posted March 3, 2011 gory detail Leica FAQ — Lens white numbers Noel Link to post Share on other sites More sharing options...
pico Posted March 3, 2011 Share #25 Posted March 3, 2011 Originally Posted by pico My 75 mm Summilux has '00' engraved just to the right of the distance scale (perpendicular to the scale lettering). Serial # 31511xx. Most likely you just didn't read that little number correctly. Have a closer look! Here it is, just as I stated. Do you not see '00'? And an a larger image here Link to post Share on other sites More sharing options...
01af Posted March 3, 2011 Share #26 Posted March 3, 2011 Here it is, just as I stated. Do you not see '00'? Yes, I do ... so my assumption was wrong. Sorry! I still think it's not the way it is supposed to be. If the lens is not really 70.0 mm or 80.0 mm—which both is equally unlikely—then the person who did the engraving made a mistake. I saw a newer Summilux-M 75 mm lens (Leica not Leitz, built-in hood, made in Germany, serial number in the 397XXXX range) that carries a '50' marking. Link to post Share on other sites More sharing options...
pico Posted March 3, 2011 Share #27 Posted March 3, 2011 Advertisement (gone after registration) Yes, I do ... so my assumption was wrong. Sorry! I still think it's not the way it is supposed to be. If the lens is not really 70.0 mm or 80.0 mm—which both is equally unlikely—then the person who did the engraving made a mistake. I saw a newer Summilux-M 75 mm lens (Leica not Leitz, built-in hood, made in Germany, serial number in the 397XXXX range) that carries a '50' marking. Yes, I have seen the same '50' on a German version. Here is another, also Canada, so perhaps they did not properly mark the earlier Canadian versions. Fortunately, this lens is right-on focus. Link to post Share on other sites More sharing options...
UliWer Posted March 3, 2011 Share #28 Posted March 3, 2011 It should be compulsory for Leica engravers to read this forum first before starting their work. Link to post Share on other sites More sharing options...
Guest #12 Posted March 3, 2011 Share #29 Posted March 3, 2011 You can measure the true focal length from the extension, sort of. Like for the longer lenses, if you can measure extension to the nearest 1/5 of a mm, you can measure the focal length to the millimeter. Link to post Share on other sites More sharing options...
01af Posted March 3, 2011 Share #30 Posted March 3, 2011 ... if you can measure extension to the nearest 1/5 of a mm, you can measure the focal length to the millimeter. That's right ... but when you happen to have another lens with a known focal length then you can determine the focal length of your lens in question in a much easier and more accurate way—by comparing the sizes of the features in the images shot with the two lenses, preferably at or near infinity. Link to post Share on other sites More sharing options...
Guest #12 Posted March 3, 2011 Share #31 Posted March 3, 2011 that is probably better, get it from the magnification or some such...but if I want to check the engravings, I don't have any lenses of known focal length. Link to post Share on other sites More sharing options...
Guest #12 Posted March 3, 2011 Share #32 Posted March 3, 2011 and there is nothing easier than measuring the difference in extension; leave the caps on and stick your calipers in the "i" in Leica, and the little circle in the rear cap. Link to post Share on other sites More sharing options...
pico Posted March 3, 2011 Share #33 Posted March 3, 2011 Here's an early 75mm Summilux marked "05". Whazat mean? Link to post Share on other sites More sharing options...
jaapv Posted March 4, 2011 Share #34 Posted March 4, 2011 Yes, I do ... so my assumption was wrong. Sorry! I still think it's not the way it is supposed to be. If the lens is not really 70.0 mm or 80.0 mm—which both is equally unlikely—then the person who did the engraving made a mistake. I saw a newer Summilux-M 75 mm lens (Leica not Leitz, built-in hood, made in Germany, serial number in the 397XXXX range) that carries a '50' marking. According to Erwin Puts in Appendix D of his compendium 00 on a 50 mm means a lens that is exactly the nominal focal length, 50.0. I guess this case is similar.05 on a 90 mm lens means 90.5 mm. Link to post Share on other sites More sharing options...
ho_co Posted March 4, 2011 Share #35 Posted March 4, 2011 ... My 75 mm Summilux has '00' engraved just to the right of the distance scale (perpendicular to the scale lettering).... Wow, that's the lens that broke Midland's back! Wetzlar had told ELC, "One more messup, and we're bringing production over here. " Unless, of course, your lens was made in Germany; then it was simply an engraving error. Link to post Share on other sites More sharing options...
pico Posted March 4, 2011 Share #36 Posted March 4, 2011 Wow, that's the lens that broke Midland's back! Wetzlar had told ELC, "One more messup, and we're bringing production over here. " Unless, of course, your lens was made in Germany; then it was simply an engraving error. I am not sure how to take that, Sir, but this lens is 100% good to me. Focus is spot-on, everything is good and by the pictures you can tell I hardly use it. - ma faut! Excuse! Link to post Share on other sites More sharing options...
PBeter Posted March 4, 2011 Share #37 Posted March 4, 2011 Yesterday I finally received my Summilux 50mm/1.4, long wait, but what a glass, great! Today was beautiful sunny weather. And made a series of school carnival, a festival for students in the marketplace of Sittard (NL) https://picasaweb.google.com/peter.bastings/Scholierencarnaval?feat=directlink Link to post Share on other sites More sharing options...
jaapv Posted March 6, 2011 Share #38 Posted March 6, 2011 Wow, that's the lens that broke Midland's back! Wetzlar had told ELC, "One more messup, and we're bringing production over here. " Unless, of course, your lens was made in Germany; then it was simply an engraving error. As above: no error but spot-on. Link to post Share on other sites More sharing options...
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