For general purposes, it is desirable to provide what are called washes of light.
Washes are general, unfocused light designed to evenly light a certain area of the stage.
Typically several different washes are used to give each scene a different feel. Often several instruments are used that can be used for general purpose filling of dark spots and other effects. Obtaining a usable dim wash is a task many lighting designers face. Many novice lighting designers think that a satisfactory dim wash can be obtained with only a few instruments. The truth of the matter is that it typically takes more instruments running at lower levels to produce a usable dim wash.