Well I did it, I bought a 17-55mm f2.8 IS - Page 3

Toby · 27-07-2010, 18:15

You're right, the nominal focal length of a lens, in this case 17-55mm, is relative to a full-frame (i.e. 35mm) sensor. If used on a crop, this thus equates to 1.6x the length, so roughly 27-88mm. You don't get different lenses for different sensors in terms of focal length ratings, but some lenses, like Canon's EFS range, only work on crop sensor cameras.

If you buy a 12mm lens then yes, on a crop camera it'll be the same as 17mm would on a full-frame camera. This isn't what you get with your 18-55 though as that would equate to 29-88

Remember that, whilst equating 12mm to 17mm makes it sound far less impressive, 17mm on a full frame sensor is still very wide angle indeed. The wide angle choice of Canon pros on full frame sensors is the 16-35

27-07-2010, 18:15	#21
Toby Absinthe Join Date: Aug 2007 Posts: 1,023	You're right, the nominal focal length of a lens, in this case 17-55mm, is relative to a full-frame (i.e. 35mm) sensor. If used on a crop, this thus equates to 1.6x the length, so roughly 27-88mm. You don't get different lenses for different sensors in terms of focal length ratings, but some lenses, like Canon's EFS range, only work on crop sensor cameras. If you buy a 12mm lens then yes, on a crop camera it'll be the same as 17mm would on a full-frame camera. This isn't what you get with your 18-55 though as that would equate to 29-88 Remember that, whilst equating 12mm to 17mm makes it sound far less impressive, 17mm on a full frame sensor is still very wide angle indeed. The wide angle choice of Canon pros on full frame sensors is the 16-35 __________________