> I agree that a mask is better if you are not sure if you would ever want
> to undo the crop. The suggestion that you cannot fade the transition if
> you delete an inverted selection is wrong, however. Of course you can,
> because you can feather the selection before you hit the delete key.

A very valid point, and of course you are right... I did not mean to
imply it's impossibility by that method, only to highlight the greater
ease with which such effects can be adjusted. For example, drawing a
polygon on the mask, and then using a number of the built-in, as well
as 3rd party, filters to affect the mask, thus providing much in the
way of creative effect.

However, by feathering a selection, you in effect apply the blur to
the entire selected area, whereas by using a mask, it can be done
sectionally. Even the humble 'Blur' family will allow a much more
diverse, and easier to work with, range of transitions.

Your point, however, is entirely well taken.