Summary: Great lens, unless you can spend $1,400 on a canon or nikon. This is my second one only because I work as a photojournalist and wear out equipment every four or five years and the first one i had was used when i got it. Sure if I could afford a name brand I would but this is the best alternative.
This is the best lens ever for the money just a no brainer
8 April 2012
Summary: At first i was prety worried about this lens even with the good reviews it has...well my bad feeling end just the day i put this pretty robust lens out of the box at firs it feels like my 55 200 Sony maybe even a litle biger i just attached it into my A580 and it became my all arround the IQ its great its almost razor sharp its really very sharp the colors i just cant explain how good the colors are almost clear of CA and pretty fast and silent and very good piece of...
Summary: I bought both the Sigma 18-50mm f/2.8 EX DC HSM Macro Lens for my Nikon D90, and a Tamron 17-50mm f/2.8 lens. I tried the Tamron first, it was ok... Then I tried the Sigma, and WOW! It was a world of difference. First was just the feel of the lens. The Sigma feels more ruggedly built, has a little more heft to it. Then there's the built in motor: Tamron loud and annoying, Sigma quiet.
Summary: Before purchasing this lens, I tried the comparable Tamron 17-50 f/2.8, but due to two faulty copies that seemed to have some sort of contact issues when used with my Nikon D50, I returned them and tried this Sigma lens. I had previously only used the kit lens and had rented the first generation Nikon 18-200 for a vacation. I liked the "one lens solution" of the 18-200 but its lack of speed left something to be desired.
Summary: Lens works great and very compact. For best results, one needs circular polerizing filter for outdoors shooting. Sigma recomends that you not double up on filters. Also, you may damage the camera if the OS is not turned off before removing the lens - this noted deep into the manual.