Automated Light Fixtures
While a detailed description of moving lights and other automatic fixtures would be too technical for beginning lighting design students, below is an overview of the most commonly-seen features:
Moving Head (or Moving Yoke)
These units work by moving the entire fixture body. Moving yoke fixtures may be “spot” fixtures, which are more tightly controlled, or “wash” fixtures, which are designed to cover (usually using several fixtures) a large area.
Moving Mirror (or Scanner)
The fixture body is stationary and the light is reflected by a mirror, which redirects the light by panning and tilting. Most automated fixtures have several features which can be manipulated to create various effects.
The most common of these are:
Pan: The movement of the field from side to side. Many fixtures have two Pan channels: one for coarse movement and one for finer, more precise, settings.
Tilt: The movement of the field up and down. Again, many fixtures have two Tilt channels.
Color: Automated fixtures can change colors in either of two ways: with dichroic filters mounted on a color wheel. The user can select only one of these colors at a time. These colors may (or may not) be replaceable. With dichroic filters in the secondary colors — Cyan, Yellow, and Magenta. These can be subtractively mixed incrementally to create an infinite palette.
Iris and/or Zoom: used to vary the diameter of the beam
Gobo: Mounted on a wheel. Some fixtures have more than one gobo wheel, allowing the user to overlap two gobos. Some of these gobos may be continuously rotatable.
Intensity: May be controlled electronically, in the case of fixtures using incandescent lamps, or mechanically, in the case of fixtures using gas-discharge lamps.
Shutter: Used to “strobe” the beam.
Other features which are found on many moving lights include prisms, distorted glass, and motor speeds. Several companies make accessories which are designed to add moving-light functionality to conventional, static, fixtures. These include moving mirrors and automated irises.