Quote:
Originally Posted by lct
Sorry to insist but at which subject distance are your focus tests done gents?
If at f/4 a given lens has a focus shift of say 10 centimeters at 2 meters who cares really? It will be compensated by DoF no?
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Hi LCT,
First, given your deep interest in these cameras and lenses (across many years) it would really be helpful to you to actually read the reviews themselves. I summarize some points when you ask me to (and have for years now) but the original source really is the best place to look. Sometimes, to really answer your questions, I'd almost need to restate an article and many of the questions you ask are covered there already.
The focus shift can be seen with subjects at five feet, ten feet, twenty feet, etc. When I say that it is a problem with normal pictures at F/2.8 and F/4.0 that's based on reviewing hundreds of pictures made in a variety of settings. DOF starts to cover for it at F/5.6 and then, more successfully, at F/8.0. I always base my reviews on a combination of field testing and controlled testing. The two together give one a fuller picture of "the thing itself".
I doubt that the focus shift in the two samples I tested is the result of a manufacturing defect. If it is not, no amount of sugar-coating or rationalization will change how the lens performs. That doesn't mean, however, that the lens will not be useful or desirable to many people. I love the Canon LTM 28/2.8 and it mostly crashes and burns when tested for optical performance.
I would imagine that many photographers will be able to say of this lens, "I know it has X,Y,Z weakness but I like it and its working well for my purposes." And who can argue with that?
At the same time, a review of a lens, that purports to really describe it, needs to look at all aspects as objectively as possible. Many lens reviews are really anecdotal reports. Those have their place, of course, but they can also be somewhat limiting. I think its best for a review to describe pros and cons, across various performance aspects, and then let the photographer decide how that mixture of strengths and weaknesses suits him or her.
Cheers,
Sean