A Measure of "Sharpness"

Is there some sort of "sharpness" scale? How can "sharpness" be measured? I can't recall any optics book that deals with the subject.

To me, it seems like an extremely subjective term that gets bandied about with wild abandon, but really provides little useful information.

Clear skies, Alan

A pretty sharp observation, Alan.

I agree and avoid the term when able. However, you got me thinking about my own use of the term "fidelity" -- hardly quantifiable in its own right, that's for sure. Maybe I tend to use it in a sort of "general/relative/overall" context.

Back to "sharpness:" if I had to relate what the term means *to me* (and only me), I might fumble/babble my way through concepts which entail...
-accuracy of image/wavefront
-"invisible" (or practically so) scatter
-lower image magnifications

Cheers & best wishes.
-Dan