Richard Knoppow: > I think yor are refering to five element Tessar type > lenses rather than the Xenotar type, which was based on work > done by C.G.Wynne of Wray in England. Wray's work was done > c.1944. > The Xenotar is, essentially, a modification of the Biotar > type where two elements are combined into one. The lens > still has the essential symmetry of the Biotar. There were a > number of Tessar type lenses with three cemented elements in > the rear, Schneider made at least one. Zeiss had a 6 element > Tessar called the Biotessar with three cemented elements in > back and two in front. I suppose it could also be considered > a Heliar type. Bausch & Lomb made an arial lens with three > cemented elements in the rear, other lenses were the Ross > Xpres (not the W.A.Xpres, which is a Plasmat) and the > Gundlach Radar. The Radar was probably designed to avoid the > Zeiss Tessar patent rather than to improve the correction. > In any case, the idea of adding an element was tried by > several makers. It would seem that other designs were more > successful in providing improved performance. > > --- > Richard Knoppow > Los Angeles, CA, USA > dickburk@xxxxxxxxxxxxx The Xenon as used on most Retinas is a 6 element Opic variant (mostly symetrical double-gauss), a pre-was design (at least the f/2 variants). Eric Goldstein --- Rollei List - Post to rollei_list@xxxxxxxxxxxxx - Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' in the subject field OR by logging into www.freelists.org - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with 'unsubscribe' in the subject field OR by logging into www.freelists.org - Online, searchable archives are available at //www.freelists.org/archives/rollei_list