Chief_10Beers wrote in post #17338867
Going back to my original question, a EF-S 17-55mm f/2.8 is 17-55 on a full frame camera but the effective range is 27-88mm on a crop that is designed for, makes no sense at all to me. Why not badge the Lens as a EF-S 27-88mm f/2.8?
Because badging EF-S lenses with a modified focal length, rather than the actual focal length, would just confuse the hell out of people. It just doesn't make sense to do that.
As it stands, an EF 50mm and an EF-S 50mm are identical focal lengths and will provide identical images on a crop camera. So if you relabel the EF-S as an 80mm, as you suggest, then you would have two lenses giving identical field of view but one is 50mm and one is 80mm. With many people, it would end up as a set of lenses labelled using two different systems.
Consider the EF-S 55-250. Doing as you suggest would rename that as an EF-S 88-400, but imagine someone considering a zoom and looking at that lens and also the EF 70-300. The numbers would now suggest that the EF-S 88-400 is longer at both ends than the EF 70-300, so give better reach for birds etc. However, the reality is that the 70-300 is actually the longer lens (by 50mm at the long end) and will give the better reach.
It is so much easier to understand when two lenses with equal field of view, are labelled the same. Why on earth would you want to confuse things, by labelling some of them with anything other than the actual focal length.
It is pointless thinking about how your lens would be on another camera, why do you need to think "this lens is 200mm, so that makes it a 320mm if it was on another camera that I don't have". The only reason would be if you were used to 35mm film cameras (for example) and wanted to compare what focal length you would need on your new digital crop body to give you the same field of view you like on your old gear.