Hello. I'm not a pro, but work for a company that likes to take a lot of photos. We currently have a Canon EOS 30D w/Sigma DC 17-70mm, 1:2.8-4.5 lens.


This lens works well enough for your typical candid-like shots, but on quite a few occasions, I'm required to take group and portrait-like still photos. On some of the group shots, I have noticed that the corners of the photo, and people on the ends, become a little out focus. Overall, the quality is not the greatest either, compared to what I've seen from others.


So I'm hoping to find a lens that performs great under some or all of the following conditions:


1. Large group still photos: the groups can get relatively large.


2. Portrait-like still photos: we have a little studio setup with a gray cloth background


3. Lower light: generally, lighting can get a little low in some of the places we take photos often.


4. If it can snap a good crisp photo that features a lot of motion, without flash, that would be a plus.


Any help would be appreciated.


-Jesse-