'are the Canon or Nikon versions better than the Contax versions?'
They are more modern, have better coatings and an extra element to make up for the loss of the special glass in the Contax, are better wide open, less good from f4 down. Don't quite have the amazing low light shadow detail and impact of the CY. They are however very close, and 20 years newer. the ZE/ZFs are a better buy IMO, for resale and condition. Vet any CY 21mm carefully, it is a lens that is hard to not use a lot.
Anyone interested in why the Leica M wide angles don't work on our cameras, see p12-13 of the Zeiss white paper on the Distagons - linked below. There is also a very informative MTF chart of the Contax 21mm and text on p6:
'Its performance, particularly the perfect correction of lateral chromatic aberration, was achieved solely by the combination of very special (and expensive) high index glass types with glass types displaying extremely high anomalous partial dispersion.'
The old-fashioned way, and they are rightly proud! It was likely a similar effort as that they put in for the Otus.
There is a good discussion on the (then new) 25mm f2 Distagon on page p6-p8.
http://blogs.zeiss.com/photo/en/wp-content/uploads/2011/12/en_CLB41_Nasse_LensNames_Distagon.pdf
They are more modern, have better coatings and an extra element to make up for the loss of the special glass in the Contax, are better wide open, less good from f4 down. Don't quite have the amazing low light shadow detail and impact of the CY. They are however very close, and 20 years newer. the ZE/ZFs are a better buy IMO, for resale and condition. Vet any CY 21mm carefully, it is a lens that is hard to not use a lot.
Anyone interested in why the Leica M wide angles don't work on our cameras, see p12-13 of the Zeiss white paper on the Distagons - linked below. There is also a very informative MTF chart of the Contax 21mm and text on p6:
'Its performance, particularly the perfect correction of lateral chromatic aberration, was achieved solely by the combination of very special (and expensive) high index glass types with glass types displaying extremely high anomalous partial dispersion.'
The old-fashioned way, and they are rightly proud! It was likely a similar effort as that they put in for the Otus.
There is a good discussion on the (then new) 25mm f2 Distagon on page p6-p8.
http://blogs.zeiss.com/photo/en/wp-content/uploads/2011/12/en_CLB41_Nasse_LensNames_Distagon.pdf