Frederick Stevens , Jan 25, 2010; 09:17 p.m.
I find the fairly standard 17-85mm IS Canon zoom OK for portraits. The lens should probably have an effective focal length of around 90mm and you never want to be too close to the subject. You need to multiply the focal length of the lens by 1.6 in the case of the 7D and this gives you a 27mm-136mm lens when using the 17-85mm zoom. The lens quality is very adequate and I feel no need to use any other lens. The lenses you mention will cost an arm and a leg and there is no need to go that route. Give the cheap 17-85mm a try! I think you will be very impressed.