It is a jack-of-all-trades, master-of-none lens, as are virtually all superzoom (10x+ zoom range) convenience lenses.
With a nearly 14x zoom range It is virtually impossible for the lens designer to account for all the technical optical aberrations the zoom range presents.
Here is a review of that lens -
Sigma 18-250mm f/3.5-6.3 DC OS HSM review: Digital Photography Review
Conclusion - Cons
- Very inconsistent sharpness through the zoom range - extremely soft at 135mm
- Soft corners at almost all focal lengths
- Image stabilization not as effective as on similar lenses, especially at telephoto end
This linked review is not for the new Macro version of Sigma's 18-250. It's for the older version. This new macro version just came out this past summer and has got some very good reviews. People need to understand that if you want a super zoom, there is a reason. Yes, it may not be a "pro" lens. But it is great for what it is. We'd like to know which of the super zooms has the best reviews so we can make an informed decision. I recently went on vacation and spent so much time switching lens, missing shots, getting dust and dirt in my camera, dragging around a heavy backpack with all my equipment in it, that when I got home I knew I wanted the super zoom. It's just a matter of which one. Please don't tell those who are in the market for one that it's a waste of time and they should buy 2 lenses instead. If I was shooting a pro job I'd probably use a different lens, but for my next trip, I'm buying a super-zoom.