"N" wrote:
If perspective has nothing to do with focal length and only relates to the
distance between the subject and camera, what makes a 50mm lens normal?

Nothing.

It's a hideous focal length: it's too short for isolating the subject and
it's too long to show the space and context the subject exists in.

It became "normal" by default. In the day of fixed lens cameras. 110mm on
6x9, 75 or 80mm on 6x6, or 50mm on 35mm have the property that they are the
shortest (widest) lens that can be made with a simple lens design (although
they are retrofocus on an SLR). Anything wider would require more expensive
optics and anything longer would make a larger and less useful for snapshots
camera.

A 50mm lens on a 6x6 or 6x7 camera, on the other hand, is a lovely focal
length.

David J. Littleboy
Tokyo, Japan