[keithpeter]

When I spent hours in a wet darkroom, I used a masking frame and the enlarger head height adjustment to crop a print, having previously marked up a work print. The negative was untouched.

The larger point I am making is that by referring to 'real' objects, we will return to a point where there is no system wide consistency any more. Case in point: editing audio tape or cine film did destroy the edited version, which is why we used prints/copy tapes.

Disclaimer: I don't use Mac OS. I do look to Apple for UI design however.