Archived posting to the Leica Users Group, 1997/03/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I am a little surprised at the negative attitude of most LUG members to POP Photo.Their optical and technical expertise is second to none in the world. I, for on, would feel honored to be able to discuss optical matters with them. We should feel a little more relaxed about other people's opinions about Leica lenses. Following the exchange of opinions about several Leica lenses in the last few months I do not get the impression that the LUG members themselves have one common denominator for lens evaluations. I do remember my first post when I made some comments on the Summicron DR and got instantly killed, because my comments were (and are not) in line with the majority. A few weeks ago somebody stated that the Noctilux 1,0 is only usefull at full aperture. On the basis of the results from the optical bench and also from *MY* practice, this is not true. But his opinion as a personal statement should be respected. Marc is right, that no optical test can do full credit to all characteristics of a lens. 'Different lenses are designed to meet different criteria', he says, which is OK. It is however possible to use ONE test to evaluate these different criteria. Astigmatism as such will be seen by every test done properly. It is the relative weight you attach to this phenomenon on which you construct your opinion or evaluation. Some examples. I measured the curvature of field of the old and new Summicron 90mm. The new one had: 0,02 and the old one: 0,07. So from the results the new one is "better". But in practice you do not see these differences. I also measured the decentring in an old Minolta lens and a new Leica lens. The Minolta had a value of 0,00 (!) and the Leica 0,04. Is the Minolta better? The Noctilux has more (measured) astigmatism at full aperture than every lens I ever tested. But is it a bad lens? My point then is: the test criteria for a lens can be defined in a quite objective and measurable manner. And that is across all lenses and different sets of criteria. Pop Photo has presumably the same set as Chasseurs d'Images or Leica or Zeiss or Canon. The interpreation of these results is what matters. And indeed we must honour the design decisions of the optical designer who has a certain optimum use in mind when balancing conflicting demands.