I own the 85/1.8 which I've used on a 30D, 40D and my new 7D. This lens is definitely worth the relatively small amount of money it costs. Autofocus is quite fast, and manual focus is much smoother than the 50/1.4.


I've heard the 100/2 is basically the 85's twin, except for a bit more
focal length and 1/3 stop less light. If you want a longer lens on a
budget that's where I'd look.


I used to shoot a lot of basketball with a 70-200/2.8 on a Full Frame film camera. Because action in basketball is often so close a zoom lens can be nice, but any 70-200/2.8 is going to run you $700+, and won't allow as fast of shutter speeds.


The 136mm equivalent of the 85/1.8 on your 50D should be a really nice compromise of focal length. A longer lens (like the 135/2) might be better for shots of the players under the far basket, but by the time they're on your side of the court, you'll definitely want a shorter lens.


While an f/1.8 lens will help you autofocus faster, I'd be wary of shooting sports wide open at f/1.8. There's not a lot of depth of field down there, and wide open is where all but the most expensive lenses suffer in sharpness. My suggestion would be to shoot stopped down to f/2.2 or so, and use f/1.8 for extra brightness in the viewfinder and faster autofocus.