edkel wrote:I understand the first part about the image sensor in a digital slr is smaller than the 35mm film frame of a film camera.
I still don't understand the focal length explaination. Is the distance between the len and the image sensor in a digital slr, different than the distance between the len and the 35 mm film frame in a film camera?
See the link posted above. If you think of it as a field of view crop factor rather than a focal length multiplier, it should be easier to understand, ie the effect of the smaller sensor is to crop the field of view of the lens giving you a field of view that, if you were using a 35mm camera, would look like it came from a lens with 1.6x the focal length.