<<Given all that I don't think your test is going to tell you what you want to
<<know. Perhaps go out to one of the marshes, angle the horizon and take a
<<at infinity, which seems to be the way they do it on FM
Thanks for the links. The methodolgy I used is very similar to Fred's. I
don't like handholding in the cold and turning the cam upside down just makes
the images easier to compare in LR.
Sharpness testing at ultrawide FL is tough but basically looking for
decentering. The air was cold and the distance essentially at infinity for the
Sigma has better QA than most and now have a way to check MTF and tweak during
production. Roger at Lensrentals has said it is usually more expensive for a
company to try and fix a decentered lens than toss it and ship our another.
I was very careful with my test methodology; the problem is determining what is
"acceptable" for intended use.
Well centered or not, Mike
Themed Olympus Photo Exhibition: http://www.tope.nl/