Hi, Q: When is a 'Carl Zeiss' lens not a 'Carl Zeiss' lens? A: When it is a Carl Zeiss 'JENA' lens.... I am posting this because as a Contax/Zeiss user, I am concerned that an increasing number of people are potentially getting misled into thinking that the old M42 screw mount Carl Zeiss 'Jena' lenses are proper Zeiss lenses, when in fact they are nothing of the sort. In particular there has been a mushroom effect in people using older lenses with adaptors on digital SLR's and sellers on a certain auction site are most certainly IMO trying to con bidders into thinking these old M42 Zeiss 'Jena' lenses are the real thing...in other words misleading bidders into thinking they are the equivalent of the 'proper' Contax Zeiss lenses. Just for the record..these M42 screw Carl Zeiss 'jena' lenses were made in Eastern Germany (DDR) run by the Russians after the end of world war two and up until the fall of the Berlin wall. The only real connection to Carl Zeiss is that they were made in the old Zeiss factory in Jena, which was 'inherited' by the Russians. It was just quite literally four walls and a roof. The proper Carl Zeiss company in Western Germany was furious that the Russians were making lenses with the Zeiss name on them and pursued a legal case for years, but this was very difficult across the west/east divide and the russians got around the issue by putting Carl Zeiss 'JENA' on their lenses. These 'Jena' lenses were mostly made for the low end Praktica cameras and are of generally low end quality with poor build and design. Some of the lenses have proven to be of good optical design, but these are very much in the minority and all the lenses suffer from poor build issues and poor longevity. You can get good results with some of the lenses, but should be aware that they are nothing like the same build quality as proper Zeiss lenses. I am stunned at how much some of the M42 Jena lenses are now fetching, indeed some buyers are now paying almost as much as you would for proper Contax Zeiss lenses! which does lead me to think they are imagining they are actually buying the real thing, when they are not..... cheers Steve.