The Sigma 30mm is fairly sharp but not stellar across the frame from F2.8 thru F8. Starting with F11, the effects of diffraction start to blur the images. I have not tested vignetting but I don't see it in my test shots and it is unlikely to be an issue because the lens was made for a larger image circle. The main problem that these test shots reveal is chromatic aberration, which can reduce the positive impression of a fairly sharp lens considerably. Interestingly, chromatic aberration is not corrected even on a Panasonic body.
Read review at: http://www.superflexible.com/photography/sigma30mm.htm
Well, since i don't need autofocus, there is no advantage vs good old manual lens from ebay :)
Gee, it sounds like a downgrade from the Sigma 30mm f1.4 legacy Four Thirds lens. It is smaller and cheaper though.
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