Quote Originally Posted by alanrockwood View Post
As pointed out above, there is no doubt that depth of field is based (to a significant degree) on a perceptual judgment.

However, it is possible to define an objective scale. Here is an example of how one might do it. [...]
"Lots of choices. Pick one." "Define" (in the "pick one" sense). "[...] perceptible by a person"
And still "an objective scale"?

Doesn't work.

The second approach, based on arbitrarily chosen ("let us say") dimensions, does no better.

As you say: "The criteria may be arbitrary"
And there the whole things come falling down. DOF is not an objective thing.

A statement like "The second method is independent of factors such as magnification, viewing distance, photo size, etc." even cannot be a thing related in any way to DOF.
DOF, in essence, is dependent on factors such as magnification, [etc.]