What factors affect optical dot gain?

A scanned image that looks fine on screen may be too dark for printing and my need to have its contrast curves adjusted. Optical dot gain (or loss) can be caused by the laser beam in certain equipment such as film imagesetters (recorder gain) and computer to plate systems. Depending on whether the process is positive or negative, a slight dot gain or a dot loss may occur. The type of material used for the plate or film may affect dot gain. In general, more dot gain will result from higher screen rulings.