Tamron 17-50 f/2.8 & Sigma 17-70 consistency of sharp images

Started Dec 2, 2007 | Discussions thread
Senior MemberPosts: 2,948
not entirely
In reply to Glenn W., Dec 5, 2007

I think you have a valid point about the optics, but I think AF control also plays a pretty big part in the AF inaccuracies we read about here.

If not, then why would Canon bother calibrating body/lens combinations for customers, and why would several new camera bodies from Canon and Nikon offer AF micro-adjustments to calibrate the body to each lens?

I agree if you have an optically bad lens to start with you aren't going to compensate with more accurate AF control. But I think you could also have good optics to start with and also have marginal AF control.

Glenn W. wrote:

It's my belief that most of the differences in focus ability, boil
down to the optics in the lens, as opposed to the signaling of the
electronics that are used by the camera and lens to communicate...
That is... I believe that if you have a very good lens, it's good
because all of the elements in the lens are aligned very well and
this then makes it relatively easy for the electronics to do their
job in focusing... If the optics of the lens have even some minor
problems, then it seems there will pretty much always be some level
of mis-focus, until you get the optics fixed.

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