Hi I am 13 and I just bought the 500d and I wondered whether to change it to 50d. The 50d has so many advantages over the 500d,eg. shutter speed, microless gap lens etc. Please give me some advice. By the way, I would like to trade my current Sigma 28-300mm telephoto lens to either a canon 24-105mm, a tamron 28-75mm, no os, canon 18-135mm.