I can't understand why so many can't grasp this, after all a xxmm lens is an xxmm lens regardless of whether it's on an 8x10 view camera or a 110 format camera. The image size is the same on all, it's just that on an 8x10 camera the image takes up a smaller portion of the film than on a 110.
It's easy to explain. Ninety-nine times out of a hundred, you select a lens with a particular focal length for a particular photo because it provides the angle of view you want for that shot. But lenses aren't identified in terms of angle of view, they're identified in terms of focal length. This leads to people measuring angle of view in millimetres, which is actually perfectly reasonable, as long as everyone understands that they're referring to the equivalent AOV that would be obtained by using a lens of that focal length on a camera with a 35mm-size sensor.
Pedantically, measuring angle of view in millimetres is abhorent, but given that it's a much more convenient measure for the majority of photographers, I personally don't have a problem with it as long as everyone understands what they're doing. :-)
S
