New K20 focusing issues...

Started Aug 12, 2009 | Discussions thread
emem
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Re: New K20 focusing issues...
In reply to Silverflower, Aug 14, 2009

Silverflower wrote:

opiecat is right, it' the lens.

I have K20 and the third copy of that Tamron (1-massive ff, 2-decentering). Has easy FF on 75/2.8 and adjusted to -4 in my AF menu. From that moment ALL pictures at 55-75mm/2.8 at any distance was right on focus and very sharp, like a cheap prime, except human error, of course.

But under 43mm started to BF slightly. Worse, it have aperture focus shift at any focal, meaning if I close diaphragm past f4 (f5.6, f8) it has BF roughly 1/10 distance from the AF target (relation with DoF, more preciselly, like half of it). Even at 75mm/f4 on close headshots portraits with focus on eyes, tip of the nose is not that clear, but ears are good. Tipically, at group shots at 28-40mm/f6.3 at 5-10meters I must focus on the front ground one step front of first in group and recompose. At 28mm, even properly focused it's not sharp enough until closing to f5.6. I forgive it all that quirks because of excelent 2.8/75mm portraits.

Your patience with testing and your powers of deduction are impressive - the above summary of your lens charecteristics and behaviour made my head swim!!
--
Mike M. (emem)
http://www.veritasmea.com

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