Gunars Grinvalds's reviews
9 out of 10 points and recommendedGood sharpness, accurate, sufficiently fast and quiet AF, solid construction, reasonable priceSomewhat high chromatic aberration in 18-50 mm zoom region
I purchased this lens last week for my Sony A200 on purpose to replace Sony's old DT3,5-5,6/18-70 kit lens. I perform some tests to compare new lens with my Sony 18-70 and Sony DT 4-5,6/55-200 lenses.reviewed March 31st, 2010 (purchased for $350)
Comparing sharpness of Sigma and Sony 18-70 I found Sigma being better by narrow margin in the center and essentially better near the corners. Sigma's sharpness gradually slightly decreases towards the long end but even at 125 mm it remains higher than sharpness of Sony 18-70.
Chromatic aberration in 18-50 mm zoom region was higher than I expected. It was less disturbing in 70-100 mm region but noticeable at 125mm again.
Comparison of sharpness between Sigma and Sony 55-200 was in favour of Sony. Sony's sharpness both in center and corners was slightly higher at all corresponding focal distances. At 200 mm sharpness of Sony remains little bit better than that of Sigma at 125mm.
Conclusions: For my great pleasure replacing the previous kit lens for Sigma 18-125 gives me much better sharpness and expands zoom range almost by factor of 2. This is nice walk around lens for reasonable price that covers 90% of everyday needs. Somewhat high chromatic aberration is obviously the fee for very versatile nature of this lens.
Sony DT 4-5,6/55-200 is excellent lens too, due to it's sharpness, convenience and good price and covers all needs for longer focal length.
P.S. I perform lens tests by shooting from tripod large sheet of newspaper supplemented with specific pictographs sticked in the center and near the corners of the frame. I evaluate sharpness and chromatic aberration visually. All shoots was taken at aperture 5,6.