CHG_CANON wrote:
24mm is 24mm on the same camera whether an EF or EF-S. There are minor technical differences, some you noted like filter size and IS. The bigger differences are ruggedness of the build as in size, weight, weather resistance and overall ability to hold up on demanding conditions for the 24L. And then there's the cost ... The 24 EFS is intended to be a small, relatively cheap, sharp, f/2.8 prime.
Well, yes and no. On a crop frame camera a 24mm EF-S Lens is just that, 24mm. On that same camera a EF (full frame) lens has a 1.6x crop factor so it actually shoots as if it were a 38mm EF-S lens. One has to consider the focal length actually needed when choosing to purchase a full frame lens for a crop frame camera body.