You only started for 4 months and you are now buying new lenses... that's quick to get on the gear head wagon LOL
IMO the 15-85 is too slow, f4~f5.6, you basically lives with a flash unless in sunny outdoor.
Go get a 1.4 normal prime! When I started with 50D+18-200, the first lens I bought was a Sigma 30mm f1.4 DC. It's pretty darn good. I didn't know what was corner sharpness and literal CA by that time so those flaws didn't bother me at all (Now you know! Ha!). It gives you a ~50mm normal angle on 1.6x Crop which is very good starting point.
Yep . I took a lot of pictures in these 4 months. Experience is the best teacher in the world as it turned out.
I think that I'll stick with my 50 1.8II for fast prime for now.
I stumbled on "Sigma AF 17-70mm f/2.8-4 DC HSM OS macro" while doing some research. The range is not of 15-85 but it seems considerably faster at 2.8-4, and provides some "semi macro" (1:2.7) which I like a lot. It also cost 450$ new!
Anyone have had any experience with it? How would you rate it next to canon 15-85? New Sigma or used Canon? hmmmm..........