Archived posting to the Leica Users Group, 1996/03/29
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Actually, it was Eric Welch who pointed out to me that Leica had recently hired away from Zeiss their new director of advanced optical design; I then reviewed the remarks he made to the LHSA annual meeting last year, where he claimed credit for changing Leica's design practices to comply with Zeiss's by using MTF data as the determiner of lens quality rather than Leica's former practice of using "final image quality" as the arbiter. However, this has only been in effect for two or three years, and thus only affects the very newest lenses. Eric deniees vehemently, pointedly, and repeatedly that Leica used residual aberrations. However, the documentation on this is pretty immense, and I suggest those interested look at the literature, such as Dr Kingslake's works or those of Rogliatti. As K D Schaefer, the Chief of Photographic Lens Design at Leitz, wrote in 1978: "...the process of criticizing image quality and balancing residual aberrations even today remains with the lens designer" in contradistinction to the use of modulation transfer function analysis. The point's not worth hammering away at: if Eric wants to believe Leitz long used MTF criteria to design their lenses, so be it. The folks at Wetzlar and, later, at Solms were unaware of this, but Eric might be right. The phrase "Leica glow" originated, I believe, in a Modern Photography review from the '50's and was popularized by Leica in their advertising for some years thereafter. Gianni Rogliatti drew my attention to this -- and to the retention of aberrations by Leica, as well as to their use of a "final image quality" standard -- in private correspondence several years ago; his knowledge derived from his frequent visits to Wetzlar and Solms and discussions with K D Schaefer and others at the plant. Best wishes, Marc msmall@roanoke.infi.net FAX: +540/343-7315 Cha robh bas fir gun ghras fir!