lars_bergquist Posted January 20, 2010 Share #41 Posted January 20, 2010 Advertisement (gone after registration) As far as I know, moulding ('pressing') cannot handle larger blank diameters than about 27mm. Only elements close to the iris diaphragm have such small sizes. So larger asphericals, such as those in the 90mm Summicron ASPH or the new Noctilux, are produced by individual grinding and polishing in numerically controlled machines. (Spherical elements are produced in batches by what is essentially a mechanised version of the hand process that Galileo and Spinoza used in the seventeenth century. At least they were when I last looked. This individual production is what makes aspherical optics extra expensive.) I might add that not all desirable optical glasses can stand the stresses of hot-moulding. It sems that many special glasses can't. No, blank-pressing technology has not advanced to that level yet where it can produce large diameter elements. Leica say specifically that the Noctilux asphericals are produced by the above process. This is the reason why I am certain that Andy is wrong, and Jaap right. The old man from the Spherical Age Link to post Share on other sites More sharing options...
Advertisement Posted January 20, 2010 Posted January 20, 2010 Hi lars_bergquist, Take a look here Leica Glass. I'm sure you'll find what you were looking for!
wizard Posted January 20, 2010 Share #42 Posted January 20, 2010 Lars, you are entirely correct about aspherical elements for the Summicron 90 asph, the Noctilux and some other lenses, they are not blankpressed, I know that. But we were talking about the front element of the MATE. I have not had a chance to measure the diameter of the front element on my lens, but it would seem to me that it is certainly not much larger in diameter than 27mm. Be that as it may, I can only tell you what the Leica guy told me, so you have to prove him wrong. Regards, Andy Link to post Share on other sites More sharing options...
jaapv Posted January 20, 2010 Share #43 Posted January 20, 2010 As far as I know, moulding ('pressing') cannot handle larger blank diameters than about 27mm. Only elements close to the iris diaphragm have such small sizes. So larger asphericals, such as those in the 90mm Summicron ASPH or the new Noctilux, are produced by individual grinding and polishing in numerically controlled machines. (Spherical elements are produced in batches by what is essentially a mechanised version of the hand process that Galileo and Spinoza used in the seventeenth century. At least they were when I last looked. This individual production is what makes aspherical optics extra expensive.) I might add that not all desirable optical glasses can stand the stresses of hot-moulding. It sems that many special glasses can't. No, blank-pressing technology has not advanced to that level yet where it can produce large diameter elements. Leica say specifically that the Noctilux asphericals are produced by the above process. This is the reason why I am certain that Andy is wrong, and Jaap right. The old man from the Spherical Age You are indeed right about the diameter, Lars. And Stefan Daniel when elaborating on this at a LUF meeting specifically spoke about blanks. Link to post Share on other sites More sharing options...
wizard Posted January 20, 2010 Share #44 Posted January 20, 2010 Jaap, the person I spoke to said (in German): "Wir hatten mit diesen Linsen extreme Probleme, das Objektiv auf Leistung zu trimmen." Please enlighten me as to how this may be understood if blanks were concerned. Best, Andy Link to post Share on other sites More sharing options...
jaapv Posted January 20, 2010 Share #45 Posted January 20, 2010 Mr. Daniel spoke about the suppliers of "Rohlinge" for this lens. Link to post Share on other sites More sharing options...
wizard Posted January 20, 2010 Share #46 Posted January 20, 2010 Jaap, that doesn't answer my question. And I don't remember the name of the person I spoke to. Oh well... Link to post Share on other sites More sharing options...
jaapv Posted January 20, 2010 Share #47 Posted January 20, 2010 Advertisement (gone after registration) Andy, Rohlinge = blanks.... Link to post Share on other sites More sharing options...
wizard Posted January 20, 2010 Share #48 Posted January 20, 2010 Jaap, sure (I DID know THAT ), but why couldn't they achieve the designed performance with those blanks if it was them (Leica) who would polish (and grind?) and coat the blanks to their OWN specifications? My understanding so far was that the precision of the parts they were given by the second source manufacturer did not meet the demanded specs, but if it was blanks that they themselves bring to perfection, then were was the problem? Andy Link to post Share on other sites More sharing options...
jaapv Posted January 20, 2010 Share #49 Posted January 20, 2010 Because the quality and with that the refractive properties of the glass were not within tolerance, Andy. It is not just the grinding of the lens, the refraction is crucial. Link to post Share on other sites More sharing options...
wizard Posted January 20, 2010 Share #50 Posted January 20, 2010 ...the refraction is crucial. Correct. If it wasn't, you could use any old bottle glass to manufacture lens elements. At the time, however, I went away with a different understanding of the problem they had. If I could only remember who it was that I had talked to... If I have a chance to meet Mr. Karbe again, I will ask him about this issue, he must know what the exact problem was (type of glass or whatever). Cheers, Andy Link to post Share on other sites More sharing options...
lars_bergquist Posted January 20, 2010 Share #51 Posted January 20, 2010 Jaap, the person I spoke to said (in German): "Wir hatten mit diesen Linsen extreme Probleme, das Objektiv auf Leistung zu trimmen." Please enlighten me as to how this may be understood if blanks were concerned. Best, Andy FIRST, the blank ('Rohling') has to be ground and polished into a lens. THEN, and not until then, this lens element -- which has now distinct optical properties, especially a focal length -- has to be integrated into the lens (the objective), which means that adjustments have to be made, often to several points in the semi-assembled lens. This has to be done regardless of how the thing arrives in Solms, as a blank or as a finished element. No matter how, it has to be 'adjusted into' the assembly. A Leica lens assembly is designed from the beginning with definite capacities for adjustments. Of course these cannot be infinite. This means that the optical properties of the glass must be kept within very definite limits. If a glass manufacturer cannot maintain the specs of the glass, asssembly difficulties mount, and so does the rejection rate. I think you may be able to imagine what a rejection of a Leica lens under assembly means, in economic terms. This design and assembly technology is very important to Leica. As you certainly know, this technology did not exist in the days of the v.2 ('rigid') 50mm Summicron. Instead, an optical package was assembled, and then its actual focal length was determined, so that the package could be assembled to one of three focusing units, each for a distinct focal length group. You can unscrew the optical cell and see the code for the focal length scratched into the metal! This procedure in incredibly primitive in the light of today's technology ... but maybe not in the eyes of ... ... the old man from the Spherical Age Link to post Share on other sites More sharing options...
wizard Posted January 20, 2010 Share #52 Posted January 20, 2010 That sounds reasonable, Lars. And yes, I knew about the different focal lengths that resulted from the old way of assembling lenses. And depending on the lens in question, that even occurs with todays Leica lenses. You will for example find Macro Elmar-M lenses with different focal lengths (someone mentioned to me that there are five or six different focal lengths, evidenced by the small numbers engraved on the lens barrel), Summicron 90 asph, Elmarit-M 90 (well, that one is gone now), and Apo Telyt 135 lenses of (slightly) varying focal length, to name just some. It seems that even the Summilux 50 asph exists in the 14 and 16 variety, translating into 51,4 and 51,6 mm focal length, respectively. Best, Andy Link to post Share on other sites More sharing options...
ho_co Posted January 21, 2010 Share #53 Posted January 21, 2010 Not sure this matters, but the second and fourth elements of the 28-35-50 both had aspherical surfaces, not the first element. From Leica's description of the MATE: Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/109695-leica-glass/?do=findComment&comment=1194548'>More sharing options...
ho_co Posted January 21, 2010 Share #54 Posted January 21, 2010 Here's a story I'm familiar with, which bears on this issue. At one time, a certain lens of Leica's was always on backorder. (Nothing new there. ) For one element, it required a glass that Leica produced in their own glass lab. One day, a glass of exactly the needed type appeared in Hoya's catalog. Everyone at Leica was happy, because this meant they could quit having to make the special glass and purchase it instead. They ordered, and went on producing special glasses for other lenses, but not for this particular lens. Then the glass arrived from Hoya, but it wasn't as specified. It was close, one measurement to 2 decimal places as I recall, but Leica needed it to 6 decimal places. Leica sent the glass back for a redo. When the second shipment arrived, it still wasn't to the specification Leica needed, and Leica returned it as well. A month passed and Leica received a letter from Hoya saying something along the line of, "We're sorry we can't meet your standards and are removing the glass from our catalog." Result: Months wasted in hope, and a much larger than usual number of backorders for that lens, since it had been removed from the glass lab production schedule in the interim. Leica put the glass back into its production schedule. Moral: You can't always get what you want, or what you need. Link to post Share on other sites More sharing options...
twittle Posted January 21, 2010 Share #55 Posted January 21, 2010 You will for example find Macro Elmar-M lenses with different focal lengths (someone mentioned to me that there are five or six different focal lengths, evidenced by the small numbers engraved on the lens barrel) Best, Andy Interesting. I have a Macro Elmar-M. Are the small engraved numbers you're talking about located under the feet mark and next to the meters mark? There is an 01 there on my example. My 75 lux has a 53 in that same location. My 35 Lux has nothing engraved there. Link to post Share on other sites More sharing options...
lars_bergquist Posted January 21, 2010 Share #56 Posted January 21, 2010 Is there a reference source where we can find out exactly what those cryptical codes mean? The old man from the Age of he Enigma Link to post Share on other sites More sharing options...
giordano Posted January 21, 2010 Share #57 Posted January 21, 2010 Is there a reference source where we can find out exactly what those cryptical codes mean? Simples! Delete the last digit of the lens's nominal focal length, append the "code" and insert a decimal point. If you have a 50mm lens marked 18, the actual focal length is 51.8mm. Marked 22, actual 52.2. A 90mm lens marked 00 is 90.0mm. Marked 99, actual 89.9. A 75mm lens marked 53 is 75.3mm. Marked 03, an engraving error. Link to post Share on other sites More sharing options...
twittle Posted January 21, 2010 Share #58 Posted January 21, 2010 I suppose it doesn't really affect anything, but that's definitely interesting to know, and I had always wondered what those little numbers meant. Link to post Share on other sites More sharing options...
lars_bergquist Posted January 22, 2010 Share #59 Posted January 22, 2010 Interesting. The only lens I own that seems to carry any such code is an old 135mm Elmarit. My 28mm Summicron ASPH, 35mm Summilux ASPH, 50mm Summilux ASPH and 90mm Elmarit-M do not have them (the v.4 35mm Summicron is away for six-bit coding). When did Leitz/Leica abandon this practice? The 135 is marked '55' which I presume means 135.5mm. The old man of dubious focal length Link to post Share on other sites More sharing options...
twittle Posted January 22, 2010 Share #60 Posted January 22, 2010 When did Leitz/Leica abandon this practice? Has to have been fairly recently if at all. After all, the Macro-Elmar-M is a current product and a relatively new member of the stable. Link to post Share on other sites More sharing options...
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