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03-27-2011, 12:47 PM   #16
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QuoteOriginally posted by Egg Salad Quote
If micro AF adjustment is lens dependent then what you experienced sounds logical.
If it is some sort of calibration error then the effect will increase/decrease with the lens elements moved apart - like it happens with a zoom lens.
What was interesting...or that I had to make some "in the field" adjustments to AF adjust setting....I actually ended up backing away from the strong "-" adjustment and ended up closer to a 0 or even slight "+" adjustment. This was all based on what I was seeing on the LCD on the back of the camera...which I presume is accurate.

It's sort of disturbing to me that after all these careful tests and adjustments, much of it was out the window once I started shooting in the field. My only conclusion is that the lens-to-subject distances I was actually shooting at were much greater than I was using during my tests.

Colour fringe tests are slightly unfair because the DA* adwell as the DA70 are more overexposed but still the Sigma beats both Pentaxes which seems legit.
Yes, the Sigma had slightly more exposure than the DA and DA* lenses so I increased the exposure (in Photoshop) so the 3rd-from-the-left gray patch in the ColorChecker Passport was the same value. But you're right, apparent fringing increases with exposure I think....and it's much worse with slight de-focusing.

It was fun doing the tests but I'll likely change the way I do it in the future...probably test them at subject distances that would be more the norm for my type of shooting.


03-27-2011, 03:01 PM   #17
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FYI, yes the Sigma HSM is a total redesign. The non-HSM one was very bad...not that sharp wide open and bad flare.

Still a bit surprised your 16-50 isn't sharper though. Your other consideration is whether 24 is wide enough for you...for doing group shots, I find it's not enough indoors sometimes, but you do have to worry about perspective distortion at the edges at 16-20mm...
03-28-2011, 10:44 AM   #18
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For me your tests are realistic. I oten shoot near MFD at near wide open. So the worst you could do. I'd even say most of my subjects are less than 3m/10ft away.

kenyee, yes, distortion is very bad on the 16-50 - the edges are almos unuseable when you need them for group shots - especially when you get close.
Surprsingly, the Samyang 8mm fisheye distorts less in the extreme borders when positioning your subject carefully.

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