View Full Version : ZM Lenses -- Name Match Optics?
Are the ZM lenses true Sonnar designs, or Planars, or Biogons, ect.? Or have the marketing people been a bit too creative?
I don't know the answer, but what makes you suspicious?
I found the new ZM planar renders very similar with Jupiter 8, and I thought J8 was also Planar design, so I guess for ZM planar they follow the same design as before.
They're true Zeiss lenses, and very on the same level as Leica in optical quality.
The Sonnar 85/2 is really a Planar. Apart from that I think the names are matching. Some people say some of the Biogon designs have some Distagon element in them, but I have no idea if that's correct.
Pretty much all lenses have deviated from the original 'pure' Planar and Biogon designs. It sounds like the Biogons have a bit of Distagon element in them (most symmetric lenses do) meaning they have a longer back focal length than a pure symmetric design would have; pg. 10 of the pdf below. Planars are Planars for the most part, even though we have no problem calling a lens with 8, 9, or 10 elements a double gaussian lens. The 85 Sonnar has been said by forum users to be a Planar and it looks like that from the diagram. But if you look at page 11 on the pdf below:
For the telelenses with a shortened back focal length, such as a Sonnar, it is exactly the reverse.
I wonder if the 85 Sonnar does have a shortened back focal length, and if so, Zeiss decided that was good enough and called it a Sonnar. Or maybe they just decided to call it a Sonnar for marketing reasons. I don't know. Looking at the diagram, the rear element IS pretty close to the mounting flange, so it is only 20 some mm away from the film plane.
Another way to look at it: None of the ZM Biogon designs would work on an SLR. Heck, even the Distagon and the Planar wouldn't work. It looks like only the Tele-Tessar could work. So all of these lenses use some design tricks that take advantage of the shorter back focal length of a rangefinder compared to a typical SLR.
Read through this:
Thanks. Just curious.
Zeiss has two other pdfs on the Tessar and Planar name as well. As far as I'm concerned, they came up with the names originally, so these three pdfs have the definitive answers, unless someone has some other info direct from Zeiss.
These have always been trade names, anyway. A Biogon is what Zeiss labels a Biogon.
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