edwardkaraa wrote: zhangyue wrote: edwardkaraa wrote:
I agree with Ron\'s assessment. My copy is very sharp from corner to corner stopped down to f/4 and smaller. F/2 comes very handy in low light. It is a very usable f/2 not like say f/1.4 on the Z* 50 Planar. Interesting to mention also that this lens has no focus shift whatsoever, which is the main problem of the Sonnar 50.
When I use the Biogon on the GXR-M, the resolving power is just amazing, even wide open at infinity. Absolutely recommended.
Edward, I did some shot test on my M9 after I acquire the 35mm f2. I found indeed there is very small focus shift. at f2 at MFD, slightly back foucsed and move to f2.8 further f4, focus become spot on.
Since it is small shift and for this focal length AND f2, it may not that obvious.
Thanks for this info, zhangyue. Interesting, because both the ZM f/2 lenses (35 and 50) are not supposed to have focus shift, or it should be so minimal as not to be detectable. However, and I am no expert mind you, what you are describing sounds to me like back focusing not focus shift. If it was focus shift, if the lens is calibrated for f/2, it should be spot on at f/2 and back focus above that. If it is calibrated for f/4, it should front focus at f/2. I will try to find some info about that.
Edward, As you may know that Zeiss lens is optimized for film IKON, thus, it is not surprised to see it is front focus due to different flange distance between Film and Digital M.
(I still suspect my Sonnar actually is benefit from this if it is not optimized at f2.8. I can;t verify if it is optimized for f2.8 to begin with, but my copy seems spot on at f2.8 at MFD.)
It is not back focus. Because I see focus plane move with Aperture. At f2, it back focus, at f2.8 it spot on, and after it, I don;t see any focus plane change any more. Since it is at MFD, I still be able to see focus plane clearly even at f4.
I guess it is small to tell. but I also suspect that is why people complain its WO performance, as it is really not obvious for weak WO from its MTF and from my experience. The reason I did this test is I shoot portrait a lot and require accurate focus on eye at about MFD. Now, I always slightly compensate it for that.
Jul 06, 2012 at 01:50 PM
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