I use in conjunction with 70-200mm f/2.8L USM on 7D. For a long time I chose between 24-105, 15-85 and 17-40, at first I settled on 15-85, he attracted me with his versatility. I used 15-85 for about 2 months, then I realized that you have to pay for versatility with a picture, and by no means do I say that 15-85 is a bad lens, no, I was just not satisfied with the clarity at 15mm focal length and with an open aperture. 24-105 universal, relatively inexpensive and reliable "L" - ka, if you doubt the choice of a lens in the range of 25 thousand, then "she" (so to speak) is ideal.