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07-31-2009, 05:49 PM   #91
Marc Sabatella's Avatar

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QuoteOriginally posted by Class A Quote
Your validation by testing does not provide a reliable answer either because I highly doubt that your testing methods lead to repeatable results in a precise manner (you called them "haphazard testing methods" yourself ).
Obviously. My goal isn't to literally *measure* the error, but just get a rough idea of how problematic it is.

I find it impressive that you can easily fix recomposition focus errors by using manual focus. With a stock focussing screen, which "lies" at such critical apertures, I personally don't stand a chance of accomplishing this.
Well, I use manual focus lenses a lot, so I've learned to predict pretty well what is going to happen to my focus zone with regard to the focus-screen-lying issue. But I'll admit to some trial-and-error as part of my methodology!

08-01-2009, 03:10 AM   #92
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QuoteOriginally posted by HeavyD Quote
I recently bought a new open boxed K10d and a Sigma 17-70mm f/2.8-4.5 lens with a Hoya Pro1 UV filter. I was having the same focus issue with the Sigma as you are. ... The Sigma is out of focus while the Pentax is perfect.

Sigma 17-70mm

This looks like typical motion blure, not soft lens. But since you are using tripod, the problem can be with Sigma's chip - if the lens tells the body incorrect focal length, the SR can cause similar effect. Can you repeat the test without SR ? Or can you analyze EXIF data for some suspicious values ?

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