Archived posting to the Leica Users Group, 1999/01/24
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]SNIP -- Jim Brick wrote: > I just read in the M6 version of Leica Fotografie International, about the > 12 ASPH, "one element with an aspheric GLASS surface". So we know at least > one surface is glass! The discussion about the 24 ASPH implies a glass ASPH. SNIP -- Jim and Dick, The "Leica Product Information Sheet for the f/2.8 21mm ASPH Elmarit-M (IX/97/HX/B)" also indicates that the aspherical element for that lense is glass. At page 2 of this Product Information Sheet, it is stated: "Like the other new wide-angle lenses for the LEICA M system, i.e., the SUMMILUX-M f/1.4/35 mm ASPH., the ELMARIT-M f/2.8/24 mm ASPH., ... the aspherical glass surface is produced by high-precision 'blank moulding'. A diamond-turned, accurately polished die manufactured from a type of ceramic is employed for this process. The die manufactured in this way corresponds perfectly in reverse to the surface of the lens to be manufactured." (Caps appear in original quote.) The authors of the article in "Viewfinder" Vol. 30, No. 1, "The 35mm f/1.4 Aspherical Summilux vs. The ASPH - Which is Better," are both highly knowledgeable Leicaphiles. The article states in part: "Ed Schwartzreich owns the earlier "Aspherical" model with the two aspherically ground glass element surfaces, and Dick Gilcreast owns the later "ASPH" model with the single aspheric surface of pressed plastic bonded onto one of the glass elements." Perhaps the difference is that the Aspherical f/1.4 contains two ground aspherically glass elements (among its other elements) and the ASPH f/1.4 contains only a single molded or pressed aspherical glass element (hence the use of the word, "plastic") among its elements. This latter comment on the meaning of a word used by someone else in a journal is sheer speculation on my part, and someone with more resources and knowledge of the two lense versions will have to contribute on this point. It should be noted that diagrams of the elements of the ASPH f/1.4 show the aspherical element in the interior of the lens element groupings and not as a front or rear element. Dick, I do not subscribe to, or have present access to the Leica Fotografie, 6/97 and 7/97 and the two articles you to which you refer, "Aspherics - The Optician's Magic Word," and "Aspheric Technologies" (in which the approach of Leica and its methods of fabricating these elements is set forth). Thanks for the references though, I will try to obtain copies of the articles. Best regards and the best of light today, Bill Caldwell