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02-27-2008, 12:42 AM   #46
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QuoteQuote:
"I guess it is an AF error."
No, it's an A lens and I did not change the focussing.

QuoteQuote:
"could just mean some sticky aperture blades on the subject lens".
No, the aperture is quick and snappy. And this is reproducible.
The A lens has larger circles continously.
Here is an expanded series:



Above I wrote:
QuoteQuote:
I have two ideas what the cause may be,
  • it could have to do with the internal focussing of the DA*. If the focal length is only 180-190mm instead of 200mm, the circles will be smaller. The distance was about 3m, so this could be possible.
  • I have the suspicion, not sure though, that the size of the circle is also dependent of the position of the aperture within the lens.


02-27-2008, 02:21 AM   #47
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QuoteOriginally posted by Gooshin Quote
which is probably the most logical conclusion, and one most unnerving.

would mirror lockup avoid such a situation if one was to use older lenses?
It would on my K10D ... to the extent that the aperture would eventually get to the right position within 2 or 10 seconds. You could take the subject lens and while removed from the camera, exercise the aperture manually to see just how it responds. If it is sticking you will notice it easily.
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