On sol 33 (the 33rd Martian day), as one of the last steps in its inspection process, the Mars Curiosity Rover removed the clear dust cover from its camera lens (and put it back on for lens protection). The difference in picture clarity is remarkable.
The pictures below were taken about five feet above the ground (from above). The patch of ground shown in the shot is about 33 inches across. Both pictures show the same patch of ground, the first with the protective cover on and the second with the cover off.
First picture with Curiosity Rover camera cover on
Second picture with Curiosity Rover camera off
Both of the images above are merely thumbnail shots as Curiosity has not sent the full-size images back yet.