Caleb,


Welcome to the forum!


I have the 15-85 on a 7D and would recommend the EFS 15-85 to anyone with a crop sensor body. The lens is very sharp, the IS is great (I routinely shoot 1/2 sec at 15 mm and 1/10 sec at 85 mm and get mostly keepers), and the focal range is very useful. Also, from 17-40, the 15-85 has a minimumaperture of f/3.5 from 15-24, f/4 from 24-35 and f/4.5 from 35 mm to 50 mm, thus the minimum aperture of the two lenses in the 17-40 mm focal range is very similar. So all that you would be gaining with the 17-40 is a red ring, weather sealing (but your body isn't weather sealed), and the ability to go FF with in 3-5 yrs (by which time who knows how good the crop camera bodies will be). And you lose 40-85 mm, which is a highly useful focal range (on a crop body, it includes most of the "portrait" range).


My recommendation between those two would be the EFS 15-85. If you want to consider a second lens, the EFS 17-55 is often recommended here on the forum and has excellent reviews. I have heard so many good things about it, I have considered buying it to have in addition to the EFS 15-85. The advantage it has is a constant f/2.8 aperture versus the greater focal range of the EFS 15-85.


BTW, for IS outdoors, think waterfalls. Water starts to blur ~1/15 of a second and you start getting really nice wispy looking water by 1/2 second exposure. So you can shoot waterfalls hand held. There are other instances where I find the IS beneficial for outdoors, such as shooting in twilight(not the movie), under tree canopies, etc.


Good luck with your decision!


Brant