Originally Posted by PaintedSaint
I believe at 55 its 5.6
In anycase, even with a flash, depending on how far off you are you prolly wont get the light needed. I dont think the xsi handles iso well above 800 at all either.
The xsi is pretty good at 1600; not fantastically amazing but it's no D40 either.
With the kit lens you're either going to get some ok shots or be totally ****ed. It's not very fast at all and I can't wait to replace mine with a 24-70 2.8 way down the road.