Gobos and Dichroics for Intelligent Lighting
Color and Texture in Automated Lighting
Color agility is among the top reasons for purchasing or renting moving lights. Depending on the specific fixture, color can be manipulated in two ways. The simplest form of color control is the color wheel. In this color changing system, a number of color filters are mounted to a disk which can be indexed or rotated continuously through the beam. The apparatus is simple and cost effective for applications where pre-determined colors are acceptable. For greater color choice, manufacturers have developed color mixing mechanisms. Color mixing in automated entertainment lighting fixtures involves tilting panes of dichroic coated glass in relation to the beam. As the angle of incidence is decreased, the saturation of the color is increased. Tilting the pane in the opposite direction changes the color toward pastel tints. Many moving lights filter cyan, magenta and yellow, although some manufacturers have produced lighting instruments that also add green or UV filters to the mechanism. In addition to color wheels and color mixing, the majority of quality moving lights will include at least a few filters for color correction. Color temperature filters allow the automated lights, which typically employ cool arc source lamps, to blend in with warmer tungsten sources that are common to theatrical, dance and worship lighting. Automated fixtures often include colored gobos which can be used to further enhance color effects.
Gobos and prisms further expand the moving light’s effects capabilities. Similar to the color wheel, a number of gobos are arranged on a disk so that they can be indexed or moved sequentially through the beam. Some fixtures employ two gobo wheels and a crossfade feature that allows the user to shift focus from one image to the next. Gobos may also be rotated in place at varying speeds to provide animated effects for simulating rain, water and fire. Prisms multiply the projected image by passing the beam through a faceted glass lens. Each facet produces a copy of the image at a slightly different focus. Prisms are a staple or arena concert style beam effects, but also offer theatrical designers an effective tool for adding dimension to their atmospheric effects, in either application, even a small amount of haze can significantly enhance the effect. Prisms can be rotated and indexed, and their effects can be altered by manipulating the optical focus.
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