Ok I am a Newbie to this site, and by reading the threads everyone here seems pretty helpful. Im also new at this whole SLR thing too, considering I just purchased my 20D a month ago. Anyway I've been reading some threads and noticing that people say that their lenses are to slow or to fast. In that case they are needed to use a flash. What does that mean, when they say their lens is to slow? Dumb question, i know. But I'm just trying to learn. Thanks.