Lotusm50
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 So why no AF from Zeiss? | |
Well, let's see. Zeiss does make AF lenses. They make AF lenses for Sinar. It's not clear if Sony's agreement with Zeiss gives Sony an exclusive on Zeiss AF lenses for small format, DSLR cameras. We don't know. I guess we will know, in some way, when and if Zeiss resurrects the Contax brand (which apparently, sometime last year, reverted back to Zeiss).
Zeiss doesn't really have it's own, in-house developed, AF technology. AF technology used in the Contax 645 and Contax N lenses was Kyocera's, and Zeiss does not currently have access to this technology. I don't know the source of the AF in the Sinar lenses but it almost certainly is someone else's.
It has been reported that licensing issues have prevented Zeiss from making AF lenses in the Nikon and Canon EF mounts. Licensing issues reportedly also prevent Zeiss from producing MF lenses in the Canon mount. producing the physical Canon mount shouldn't be a problem -- the EF bayonet mount is now over 20 years old. It is the communication protocols that allow the camera to set and control the aperture that are at issue (I believe). These have continued to evolve/change over time and are presumably patented in some way and supplemented with tightly guarded trade secrets. It can be reverse engineered (like Sigma and Conurus have done) but as Sigma's experience has shown, it can be problematic -- particularly when Canon introduces new bodies. Canon could have threatened to sue Zeiss over it (whether valid or not), and I would suggest that the small market for MF Canon mount lenses (the incremental volume over those using the ZF or ZS lenses with an adapter on a Canon) wasn't worth the cost of a legal battle.
I would also point out that generally speaking you can not just take a MF focus lens and add AF technology to make it an AF lens. They are different designs. AF lenses are usually internal focusing lenses, and most of the Zeiss' MF are not. As far as I know, the only Zeiss MF design that has been made into an AF lens is the 50mm planar design (the same basic optical design for the Contax RTS 50/1.4 lens was used for the AF Contax N 50/1.4). Other lenses, like the 85/1.4 Planar have to be re-designed. It's a matter of how much glass you have to move, and with MF lenses there is usually too much glass to move effectively with AF. AF lenses, at least initially were a compromise. They had to be designed a new way and there was little experience designing lenses that way. Consequently, initially AF lenses were generally pretty poor. Today, the differences in attainable optical quality between AF and MF has been minimized. But more is still possible with an MF than an AF design. Essentially, AF lenses have a design constraint that MF do not have, and it matters.
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They seems to be keeping busy and they are developing all sorts of products. 
