Archived posting to the Leica Users Group, 2005/01/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I think there is a big difference between floating elements to correct aberrations at different focus distances and a mechanism to correction for focus shift with aperture, which would require some sort of linkage between the aperture ring and the focus ring - not something I have heard of before. On 10 Jan, 2005, at 19:42, Bill Marshall wrote: > Alex Hurst wrote: >> "FWIW, this would seem to be a variation on the Nikon CRC system >> which optimizes focus in close." > > You may be on to something, Alex, because the 85/2 ZM Sonnar does > employ floating elements, which is exactly what Nikon's CRC design > does. In the CRC (close range correction) system, these 'floating" > elements move within the lens as the focus distance changes. The ZM > 85/2.8 also "incorporates an ultra-precise, nonlinear RF coupling > mechanism" paired with the floating element design. Nikon uses its CRC > system not only with medium telephoto lenses but also with extreme > wide angle lenses, where such focus problems & resultant image > deterioration also occur. Sure enough, the new 15/2.8 ZM Distagon > employs a floating element design as well. These are the 2 new Zeiss > lenses that will be manufactured directly by Zeiss in Germany & have > not been subcontracted to Cosina because of their lack of experience & > equipment necessary for this type of lens manufacture. > > I wonder if they are also using something similar or equivalent to > Nikon's ED glass, which they employ especially on their ultra-wide > angle optics. Zeiss too stresses in its literature the use of "exotic > optical materials"* in the manufacure of the 15/2.8. It's interesting > to note as well that Nikon lenses using ED glass also employ special > focusing mechanics to accomodate "a shift in the focus point" (from > "The Nikon Compendium"). For Nikon, too, these are among their most > expensive lenses "due to the unusually high manufacturing costs > involved in the production of ED lenses." > > Funny thing is that no one called it "hype" when Nikon introduced the > CRC system. What is the resistance to this new Zeiss product line that > prompts such comments? > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >