Q: Why do you recommend the Canon EF-S 17-55mm f/2.8 IS Lens for crop DSLR and the Canon EF 16-35mm f/2.8L II Lens for full frame DSLR? Is it for the EF and EF-S reason? Cost? Or the crop factor?
A: Even though Canon DSLRs that are NOT full frame (1.6 crop factor such as the Rebel T2i, 60D, 7D) can use EF lenses, I still recommend the Canon EF-S 17-55 f/2.8 IS Lens over the Canon EF 16-35mm f/2.8L II Lens for the following reasons:
- it has a longer focal length
- it has image stabilization
- it's cheaper
However, if you're planning to go full frame soon, i.e., within the next year or so, then you should really consider getting the Canon EF 16-35mm f/2.8L II Lens.
Note that a full frame camera like the Canon EOS 5D Mark II does NOT take lenses that are EF-S mount so you can't use the Canon EF-S 17-55 f/2.8 IS Lens on a full frame camera.
