Nick_S Posted August 2, 2011 Share #21 Posted August 2, 2011 Advertisement (gone after registration) The values may well be true, but where do you measure film? On the surface, in the middle or on the carrier layer? That is more than 0.04 mm.... One would need Leica's rationale for choosing their value to see what this means. Film manufacturers will know the width of the active layers together with their batch to batch variance, film curvature etc. I would have thought that placing the active slice of a digital sensor in the mean central depth location of the optically sensitive part of the emulsion, across a variety of films, would minimize focus shift across both systems. It would be interesting to know the theoretical calculations used. Perhaps the difference of 0.04mm is the approximation to this. In which case why was the suggestion made that it is a constant error across the two types of systems which requires different lens calibration for each type of system? This is different from the suggestion that certain in-tolerance samples from two manufacturers give an out of tolerance result when combined together. Nick Link to post Share on other sites More sharing options...
Advertisement Posted August 2, 2011 Posted August 2, 2011 Hi Nick_S, Take a look here Zeiss lenses from july 2011. I'm sure you'll find what you were looking for!
jaapv Posted August 2, 2011 Share #22 Posted August 2, 2011 Film manufacturers will know the width of the active layers together with their batch to batch variance, film curvature etc. I would have thought that placing the active slice of a digital sensor in the mean central depth location of the optically sensitive part of the emulsion, across a variety of films, would minimize focus shift across both systems. It would be interesting to know the theoretical calculations used.Exactly! Perhaps the difference of 0.04mm is the approximation to this. In which case why was the suggestion made that it is a constant error across the two types of systems which requires different lens calibration for each type of system? Exactly again and this is the red paint on the herring This is different from the suggestion that certain in-tolerance samples from two manufacturers give an out of tolerance result when combined together. Nick No, that was not my suggestion. It is well documented that the tolerance variation in film is so much larger than on a sensor (because of film thickness and flatness problems) that the tolerance span on a lens used for film can be a magnitude wider than the tolerance span of a lens used on a sensor. Between manufacturers standardisation should make sure that the base values are identical. Link to post Share on other sites More sharing options...
jankap Posted August 2, 2011 Share #23 Posted August 2, 2011 Assuming, that film and sensor characteristics are different. Why cannot this be solved in modifying the camera? I accept, that single lenses can be optimized, if they are at the border of the tolerance of the fabrication. But I cannot understand, why a company should have to offer a new fleet of lenses for sensor cameras. The image area is flat in case of a sensor and (perhaps somewhat less) flat in case of film. Jan Link to post Share on other sites More sharing options...
jaapv Posted August 2, 2011 Share #24 Posted August 2, 2011 :confused:Nobody at Leica, Zeiss or Voigtlander is offering a new fleet of lenses. The only concession Leica did to the digital age in this respect is tightening up the focussing adjustment tolerances on all new lenses, or indeed any lens that comes to CS as well. It is not relevant to resolve the difference in the camera. Film is a totally different medium (as film users never tire of reminding us;)) In fact the discrepancy in register distance noted above may be the only modification needed or possible to enable all lenses to function equally well on both types of receptor, which they do. Link to post Share on other sites More sharing options...
250swb Posted August 2, 2011 Share #25 Posted August 2, 2011 Basically it says: "Yes we know we would need to adjust our product more precisely for a sensor than for film. However, we are not about to do that, so if your lens misfocusses on a digital body we do not take responsiblity, as we adjust our lenses to the less precise level needed for film." . So all this announcement amounts to is Zeiss reminding people that their lenses are adjusted to a certain tolerance compatible with a film camera, and it is presumably the same tolerance they have always used. It doesn't sound to me like they either had a previously higher standard, or had digital vs film lenses. Its all a panic over nothing. Steve Link to post Share on other sites More sharing options...
andybarton Posted August 2, 2011 Share #26 Posted August 2, 2011 Leica don't make "digital lenses", or "film lenses". They just make "lenses". Link to post Share on other sites More sharing options...
jaapv Posted August 2, 2011 Share #27 Posted August 2, 2011 Advertisement (gone after registration) So all this announcement amounts to is Zeiss reminding people that their lenses are adjusted to a certain tolerance compatible with a film camera, and it is presumably the same tolerance they have always used. It doesn't sound to me like they either had a previously higher standard, or had digital vs film lenses. Its all a panic over nothing. Steve Yup Link to post Share on other sites More sharing options...
bill Posted August 2, 2011 Share #28 Posted August 2, 2011 Keith, I use my Sonnar 1.5 on my film Ms exclusively, for obvious reasons. I returned it to Zeiss to have it optimised for f1.5 and it is worth doing. As to the rest of this thread, approaching it logically I can see no conceivable benefit for Zeiss to deliberately go out of their way to make lenses that misfocus with the M9. The point has already been made above, eloquently and well, that the plane of focus with film has tolerance relative to the thickness of the film and that of a digital sensor is planar (no pun intended). Zeiss are not going to build lenses that are unusable with Leica bodies, film or digital, but it is apparent that some require adjustment, as have Leica lenses. Regards, Bill Link to post Share on other sites More sharing options...
tompoes Posted August 2, 2011 Author Share #29 Posted August 2, 2011 That is the logic. Zeiss will not ruin its own market and they will make sure that these lenses perform on a M 9. If not, we can benefit from the exellent return policies from the suppliers. The users are not at risk. Link to post Share on other sites More sharing options...
ho_co Posted August 2, 2011 Share #30 Posted August 2, 2011 Film manufacturers will know the width of the active layers together with their batch to batch variance, film curvature etc.... Nick, remember that Zeiss and Leica designed their lenses for opposite film curvature. That is, everyone agrees that film doesn't lie flat in the "film tunnel." But whether it curves forward or backward from the "film plane" position is viewed differently by Leica and Zeiss. (Check out E Puts on the topic; I learned this from one of his Zeiss/Leica comparisons.) If you've still got a film camera, load it with a throwaway roll, then open the shutter on B and look at the film in the film gate. It's nowhere near flat. The description Andy gave above, that "it's all over the place" is quite accurate. (BTW, Leica's film tunnel is tighter than other manufacturers', for whatever that might be worth.) Link to post Share on other sites More sharing options...
Nick_S Posted August 3, 2011 Share #31 Posted August 3, 2011 Nick, remember that Zeiss and Leica designed their lenses for opposite film curvature. That is, everyone agrees that film doesn't lie flat in the "film tunnel." But whether it curves forward or backward from the "film plane" position is viewed differently by Leica and Zeiss. (Check out E Puts on the topic; I learned this from one of his Zeiss/Leica comparisons.) I suppose that might account for some of the differences observed in mounting lenses calibrated for film M bodies to digital, i.e., two alternative conventions for calibrating lenses for use with film. Do you remember which Puts article this was? Nick Link to post Share on other sites More sharing options...
christoph_d Posted August 3, 2011 Share #32 Posted August 3, 2011 Dear all, Zeiss may have stopped producing the 2/85. Can't find it on their webshop now. From what I have read it seemed to have been a nice lens, and it is always a pity to loose potential lens options... Rgds Christoph Link to post Share on other sites More sharing options...
ho_co Posted August 3, 2011 Share #33 Posted August 3, 2011 ... Do you remember which Puts article this was? Sorry, no. Link to post Share on other sites More sharing options...
Nick_S Posted August 3, 2011 Share #34 Posted August 3, 2011 Sorry, no. Howard, no problem. I'll pop the link in here, if I come across it next time I peruse his site. Nick Link to post Share on other sites More sharing options...
Nick_S Posted August 3, 2011 Share #35 Posted August 3, 2011 Following on from Howard's suggestion, a bit of digging around on Erwin Puts' site reveals the following differences in the way Zeiss and Leica consider the location of the (empirical) film plane: "Most interesting is the adjustment for the optimum focus plane. In theory you want the true focus plane to coincide with the location of the film plane in the film gate. But the true (or paraxial) focal plane does not necessarily give you the best overall contrast at a target of let us say 20 lp/mm. All ZM lenses had an adjustment in the minus direction, which is in front of the film plane. The Leica lenses were adjusted to the plus side, that is behind the (theoretical) film plane. From these figures it is clear that Zeiss assumes that the film surface is bulging outward, where the Leica designers assume that the film is curved inwards, or at least that the optimum location is in the emulsion layer and not slightly forward. We are talking here is quite small dimensions, a thickness of a handful of (human) hairs, but it may be significant. This type of adjustment may be an additional factor in the misalignment of the Konica lenses for the KM mount when being used in the M environment." Quoted from his article The new Zeiss ZM lenses 1:Theory, located here ZM lenses Nick Link to post Share on other sites More sharing options...
glenerrolrd Posted August 3, 2011 Share #36 Posted August 3, 2011 Early in the first year of the M8 I had very difficult time getting my fast M lenses (summiluxes and noctilux ) calibrated . In fact the the 2 x 50mm and the 75mm each made 3-4 trips to Solms. During this process it became obvious that the “within specifications” being used by the factory were not sufficiently tight to insure optimum calibration. There is a test for the sensor alignment where the technician simply puts the camera on a piece of test equipment and obtains a readout . There is an acceptable range ..if the sensor is within the range theoretically you should be able to adjust the rangefinder to create a good result . One M8 was right in the middle and the other just outside the limits . Lenses had a similar test on I believe a collimeter ..lets say the range was zero -100 . The acceptable range was 20-80 (as I remember it) . This was established for film camera standards (even said so on the test reports sent with the lens ..final test was film). The lens technician explained that the lenses needed to test between 20-50 to insure that the rangefinder could be adjusted precisely enough for the M8. To make matters worse it seemed that getting the fast lenses between 20-50 was very difficult ..maybe beyond the limits controlled by shimming . Why else could they never hit the range when it was written right on the service order. Finally my Noctilux and 75 Summiluxes were rebuilt .....I paid for part of the repair and it was really worth it as both lenses are now favorites . But I don t believe that Popflash is responding to the inherent tighter tolerances for digital. Rather he is saying that the lenses are set up specifically to hit the optimum for the zeiss film camera and this is slightly different than the placement of the M9 sensor . He is giving us the exact change needed and that Zeiss will do this for you at the factory. You will always have tolerances to contend with the sensor,the lens and the rangefinder . But to calibrate a set of lenses they have to all be to standard or they will never be truly inter changeable. Link to post Share on other sites More sharing options...
FlorianM Posted August 7, 2011 Share #37 Posted August 7, 2011 FWIW I have a new C Sonnar and having heard of these focus issues I did test it, and yes, it front focuses at f 1.5 and f2. It's fairly trivial to adjust your focusing for the difference. For the curious there is a post on my (tiny) blog about it. Link to post Share on other sites More sharing options...
MarkP Posted August 7, 2011 Share #38 Posted August 7, 2011 Keith, I use my Sonnar 1.5 on my film Ms exclusively, for obvious reasons. I returned it to Zeiss to have it optimised for f1.5 and it is worth doing. Regards, Bill I fully agree. Just got the lens back from Zeiss: FFD adjusted for f1.5, done under warranty, polite letter explaining the adjustment, less than 2 week turnaround from the time I sent the lens, Zeiss covered the return shipping cost. Lens is now spot on. Outstanding service! Mark Link to post Share on other sites More sharing options...
Keith (M) Posted August 7, 2011 Share #39 Posted August 7, 2011 Thanks for the info. I mentioned in a thread on the C-Sonnar 50mm f1.5 that my new lens does front-focuses slightly on my M9 but I can see no sign of it on my M7. Example from the M7 at f1.5 below. I may well send it to Zeiss for the optimisation but not until I return from my forthcoming lengthy trip. Link to post Share on other sites More sharing options...
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