DA 17-70/4 Focus Shift??

Started 4 months ago | Questions thread
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zos xavius
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DA 17-70/4 Focus Shift??
4 months ago

Since nobody at PF wants to answer, I'll ask this here....

I have a DA17-70 and while I really love it, I'm finding getting the focus calibrated at infinity is rather hard. First of all if you let this lens focus to infinity at 17mm, the edges are soft @ f4. If you turn the ring to the stop (past infinity) they sharpen right up and the center loses focus slightly. Looks like field curvature to me, but even closer objects snap into focus, so this is somewhat perplexing. I can live with just shifting focus to the stop at 17mm, but the real problem is that if I calibrate focus at 70mm I get +5. At the 17mm end, 0-1 seems to be about right at infinity. The lens, when in focus, is pretty darned sharp through its whole range and even wide open with only coma hurting sharpness wide open. So, I'm thinking there's probably nothing relly wrong with this lens, but its behavior is a little disconcerting. Manually focusing is almost impossible with it (especially at 70mm) due to the short throw of course. Anyone have this lens and have any thoughts. Looking through user reviews and comments it seems most people think that 70mm at infinity is never sharp or in focus. I think this may be the reason. It doesn't focus shift through apertures, but its certainly a bit different at both ends. Anyone have any ideas??

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