Many Film and TV productions often use constant lighting in the studio and on location, and because some types of bulbs cannot be electrically dimmed because of their design, scrims are used to reduce the intensity of the light.
This is because tungsten / incandescent bulbs will progressively change in colour temperature, becoming more orange, as they are dimmed.
Scrims are therefore regarded as a “colour safe” alternative to electrically dimming lights, and are a fine wire mesh available in different strengths, placed directly in front of the light.
A half scrim, as the name suggests, has only has the mesh half way across, which will allow the full intensity of light to fall on part of a scene. A graduated scrim varies the intensity of light from across it.