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The Zeiss Touit 12/2.8 and AF Hunting


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NEX cameras have a complex relationship between the focusing aperture and working aperture which depends on the mode used, and the light level. If you use Program mode, instead of A which is my normal choice, the lens will actually focus at full aperture - but if you use A, and set for example f/8, the lens will try to focus at f/8 in bright light but may open to f/3.5 (the default aperture also used for video) to focus in low light levels. It's a bit hard to remember exactly how the behaviour varies.

 

Try setting some different modes and apertures, and looking at your lens from the front, to study exactly what happens with the aperture. The 12mm, if it tries to focus at a stopped down aperture, will probably not focus accurately at all as the depth of field is so great it will confirm focus at any random distance between say 1m and infinity, when set to f/11. It absolutely needs to be at f/2.8 when focusing, to get the benefit of the Zeiss quality and avoid slow focus issues causes by not being able to detect any changes in contrast.

 

Study it and report back. I think you'll find your solution.

 

David, I will have to do some tests with my Fuji X-E1 - a quick test in low light hinted at a possible similar issue. Might explain the occasional slow hunting of the 55-200

esp in low light. It might be a "feature" of CSC generally.

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As some of you may have guessed, I returned the lens this morning; a $1,360.94 weight has been lifted from my shoulders. I bought the lens on Monday (what was I thinking?) and returned it to Adorama today. When they asked me why, I told them:

 

"The Carl Zeiss AF system is not ready for prime time, and I'm not interested in paying a major manufacturer big money to do their beta testing."

 

I think you did the right thing there Ed. It just didn't work out. Mind you, had you not had the AF issue, would you have retained the lens? 

 

On the beta testing, boy do I know what that's like. These companies should know better by now.

Edited by Gervais Montacute
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Gervais, I wonder if I would have kept the 12mm if there had been no AF problem. I fear I might have, and it would have been a bad decision. When I was doing assignments, I owned and used a bunch of exotic glass: the 15mm, the 16 full-frame fisheye, a 28 PC and a 500mm mirror lens. These days, being retired and just shooting stock in NYC, my equipment needs are very different; I can just carry basic gear. The Carl Zeiss Touit 12/2.8 was way out on the edge of my needs. It would have been a silly addition to my 16, 24, 30 and 50. So it's all for the best in this best of all possible worlds. 

 

Ed

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