Sunday, April 07, 2002, 1:46:54 PM, Łukasz wrote: ŁK> But isn't Xenotar the same as the Planar only made by Schneider? ŁK> Łukasz
Well, It's like saying all Tessars are the same... While the original Tessar was f/6.8, later tweaked to get f/4.5 and even f/2.8, all by changing the diopter strengths and spacing of the various elements. So now, some tessars are simply much better than others. Also, remember that it can be complicated by using strange glass types, like rare-earth Lanthanum glass, to improve the element refraction index. IIRC Kodak used such glass in some Tessar formula lenses Ektars, and one USSR made Tessar used La glass too, to improve it a lot. A "planar" is similar, the original Planar developed by Rudolph soemitime in 1890s evolved into different planars... the Zeiss one, the Zeiss Jena Biometar (which has different split element into group. Some say the Biometar 2.8/80 is better than the Planar 2.8/80...). The Xenotar, etc... All might be derived from the same old Rudolph's Planar, but vary slightly or more. And the Russian lenses, most of the Helioses are Leitz Summilux copies IIRC, but more or less tweaked... As well as almost all 1.4/50 lenses are of quite "generic" gaussian design, but they can differ a lot in quality between manufacturers. Good light, Frantisek Vlcek - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
