To get a good idea of the range of sharpness in your portable digital projector, adjust the sharpness levels all the way to the maximum level and the minimum. Examine how the picture quality changes at both levels.
To start, go all the way to the maximum sharpness level. Then slowly edge downwards until the hard distorted edges start to disappear. Adjust the sharpness level until the edges are crisp but not distorted.
Some portable digital projectors also have a color temperature setting. These predefined profiles are unique to each projector and are set by the manufacturer. You may wish to use these profiles as a starting point for calibrating your projector.