Ian,
yeah, that's the problem with digital. i'm shooting RAW so i have to specify my own USM, curves values in photoshop.
my jpeg output is questionable, or i don't like it at all.
anyway, if you shoot jpeg, there's post processing done real time by DIGIC I or II if you'r using Canon and maybe choosing parameters a.k.a Picture Styles; or VENUS engine if you're using panasonic/lumix/leica thing.. w/c will make an image for you.
one way or another, these engines, even the photoshop ones just do 3-4 basic things to convert raw data into image; interpolate sensor data, apply Curves, aplly USM, and apply saturation level.
If you read manual from canon, they suggest that you have to apply USM even if you shoot jpg








