I recently had been called to take a photo of a 100+ group. The photos were taken inside with some bright lighting. Subjects were sitting in 4 rows of a choir seats. There were fluorescent and flood light overhead. I also brought three flashes with me and set two on the sides pointed upwards into white ceiling and one on the camera body.
I was using Nikon D90 with 18-200mm Nikon lens. The pictures were taken at 22mm. This was my first time taking pictures of such large group. I never done anything more than 40 people in one shot. Basically the pictures came out really bad. The focus on the sides of the photo is just awful. The color of the photo is ok, but could be better.
In my defense I had no time to prepare. The friend called me late evening to take pictures next morning. Anyway, my question is what could I have done better in this situation? How does one take pictures of such large groups?