[quote name='fotomanic' timestamp='1285864962' post='3401']
As far as I can understand this would be the so called "stop down" working mode, the same you have to use with old lenses like Contax 35mm... am I right? The viewfinder gets darker and darker as you close diaphragm, until you can't judge focus. I still can't understand if the metering system of the camera work with the lens, but maybe I already know enough to realize it was a silly idea. I'll take the ZE version and maybe an "eos to e-mount" adapter to use 50mm on Nex-5. Thanks for your reply. Nicola
The metering will work with any EOS camera. It is Nikon cameras who do not meter with certain lenses.
With Canon, if the camera lens does not give aperture information, metering does not get adjusted to the set aperture, as there will not be an aperture set on the camera. The camera then just meters what it sees... whether the lens is wide open, or stopped down.
Like Pinhole says, it is not a good idea to get a Canon mount version of the lens to use on your NEX, as you will not be able to close down aperture.
I would seriously think about what is the use of each lens on the NEX, and choose mount according to that. To me, the 21mm Zeiss on NEX makes no sense... the compactness argument disappears... and you do have a 5D mk II to do a better job when compactness is no argument anymore.
A Voigtlander 20mm f3.5 SL II would make more sense for the NEX...