Archived posting to the Leica Users Group, 2004/11/07
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Erwin's book states that the 28 ASPH is a pressed blank aspherical surface FWIW. 2000 of the original 35mm f1.4 Aspherical were supposed to be made though some commentators said they stopped production well short of this as they were not economic to make (like the R 35-70 f2.8 perhaps). They were clearly developing the hot press technique so it makes sense to drop an uneconomic lens and replace it with an equivalent. As long as the required accuracy is achieved I imagine that a pressed aspheric would be the best choice for production. Frank On 7 Nov, 2004, at 14:28, William G. Lamb, III wrote: > > Frank, > > Correct me if I'm wrong, but I believe several sources state that the > 28 ASPH also has a ground aspherical element. It is currently my fave. > That first 35 Lux ASPH is pretty rare, isn't it? Do you know how many > were made? It might be a plus that the 50 ASPH now has a ground > Aspherical surface. Wonder whether it's true. Irwin's initial review > stated that the element is pressed. > > William > > At 09:37 AM 11/07/2004 +0000, you wrote: >> Hi Sander, >> I did check whether this new batch of titanium stuff was still a >> coating or not. It states explicitly on the Leica website that the >> limited edition is made with solid titanium not a coating. >> I had not read that the Asph surfaces are no longer pressed. I know >> the asph surfaces for the f1.2 Noctilux and original 35mm f1.4 >> Aspherical (which is my most used lens BTW) were ground and the scrap >> was rate high. I know that the immediately subsequent asph surfaces >> were hot pressed. I had heard that there were problems pressing the >> asph surface for the 90 AA, but had not heard they had reverted to a >> ground surface. I had not heardl that any recent lenses were ground >> aspherics. The "mass" production of ground aspherics is certainly >> feasible now as they are used on the larger elements in Canon >> aspheric lenses, but AFAIK grinding is only used when the element is >> too big for hot pressing. >> I believe that the 35-70 f2.8 was dropped because it proved >> uneconomic to make to the desired tolerances, was this a problem with >> aspheric surfaces? >> Frank > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >