I have no way to get any flash gear into my booth. In answer to what a dealer is, it's pretty much what it sounds like. In my booth we sell anime DVDs, and pretty much everyone I get my shots of are on the other side of the tables we have all of our stuff set up on. It pretty much forces me into a point and shoot type of situation where I can't really use the built in flash (lens shadow anyone?). The only things I have control over due to the speed at which I have to take the pictures is the zoom on my lens, shutter speed, and aperture.
I do have to say thanks for clearing that up about the 30. It would be too long for me. The FA31 would be too long too.
All I really care about is the subject in the middle of my shots, so any softness in the background or the edges really doesn't bother me. The subject being someone who is dressed as an anime or game character.
Here are 2 examples of what conditions I have to deal with from the last convention, and the third one is one of the guys sitting inside the booth, so you can see an example of what I am taking my pictures across. Ohh, and the area is normally VERY crowded, but for a quick shot I can normally get people to open a space for me as long as it does not take very long to get the shot.
So now you can see what I have to work with.
Again, pretty much everything is taken at the 18-22 mm range, and a flash is pretty much a no-go sicne I have to grab the camera right away between taking money and handing DVDs over.
So, does that mean the Sigma 20mm f/1.8 is the best one for me? All I care about is my subject, forget the background. If I can ever get out and away to do outdoors photography during the con it may be a different story.