The telephoto L lenses make a lot of sense for crop cameras: you get what you pay for.


But normal and wide angle L lenses do not make sense for crop cameras. Compared to the 17-55 f/2.8 IS, they cost more, have no wide angle, have lower quality, slower aperture, heavier weight, and/or no I.S. But they do have better build quality.
  • 16-35 f/2.8 II: not as much zoom, no IS, expensive, image quality not as good as 17-55 f/2.8 IS. Better build.
  • 17-40 f/4: not as much zoom, no IS, half the aperture, image quality not as good. Cheaper and better build.
  • 24-105 f/4 IS: no wide angle, half the aperture, image quality not as good. Longer telephoto reach and better build.
  • 24-70 f/2.8: no wide angle, image quality not as good. Better build.



All those lenses are great on a full frame camera, but on a crop much of the advantage is lost. If you upgrade to full frame some day, you can keep your EF-S lenses as a backup body or for telephoto reach. Since they cost one-third the price of full frame, it's much cheaper to stay with the small sensor system if you can. (Not to mention much higher competition, more frequent body upgrades, etc.)


The 17-55 f/2.8 is "L" image quality, it just doesn't have build quality to match.