actually when i'm using the lens indoors (24-105) i find it a bit slow but its ok with me..bump up the iso or use the 430EXII but having a f2.8 lens would be much better i suppose. another thing is i'm confused whether just get a 24-70 to replace the 24-105 or get one of the 70-200, either the f4 IS or the f2.8 IS mark II.