Also, check through your camera's options... Many (all?) of the current AxxxIS series cameras have adjustable contrast, sharpness, and saturation settings (-2, -1, 0, +1, +2).
For the A720IS (and confirmed available in the A590IS), set your mode to "P" or one of the manual modes. (not available in the automatic modes).
Push "Func/Set" to get the menus on the left of your screen.
Scroll down below "drive" (or the square box) and you will find (what I guess to be a paint brush). Use the "left/right" arrows to scroll to "Custom Colors". Push "Disp" once, and use the left/right to set value, and the up/down arrows to select the three different variables (contrast, sharpness, and saturation). Push "Disp" to exit the menu.
Note that once you put "extra sharpness" in--it can make post processing in Photo Shop a bit more problematic as you may get more artifacts around edges that PP/PS will just make worse.
-Bill