8 out of 10 points and recommendedOS, wide range zoom, low cost, small size, good buildCorner softness
I had a non OS Sigma 18-200 and it was a nice little walk around lens. Took very nice shots with my Canon XTi. I upgraded to the OS version to get the OS function. It seems to work well – probably provides me with 2-3 stops performance and saves a lot of shots for me in less than bright light. Focus is fast / accurate and the operation is quiet.reviewed May 27th, 2008 (purchased for $450)
I did notice that in all focal lengths the center sharpness and contrast was better than my non OS version (I did many comparison shots on a tripod), but that at many focal lengths the corners have more blur than the non OS version (Upper right being the worst by far and lower left being slightly worse than the other corners).
Since most of my shots are landscape in nature with a stronger ‘central interest point’ it really doesn’t show up too much in real life looking at prints – only when pixel peeping can it be seen (for instance in tree leaves at the edges of the frame).
I rarely work wide open except when I want minimum Depth of Field and usually work at f8 to f11.
The lens is quite sharp and does a good job with larger flowers in close up work – it has acceptably good close focus range for a walk around lens.
All in all I like the lens and find that its reach is very good – about 29 to 320 mm / 35 mm equiv on my Canon XTi. If it needs to be super sharp anywhere it’s at the long end and the lens performs well there.
If the corners were sharper then I would have rated the image quality higher since the center is very good.
I would buy it again.