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WPI Technical Theatre Handbook: Patterns
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Often times it is desirable to project a pattern on to the scene being lit. This can be a very striking effect, and is usually inexpensive to achieve. The basic concept is fairly simple; a pattern is cut into a small piece of metal and placed into the focal point inside of an ellipsoidal reflector spotlight. With appropriate focusing, the pattern will be enlarged and projected by the instrument. The sheet of metal with the pattern cut in it is typically referred to as a gobo in the industry, and figure 5.12 shows some of the available patterns.

Figure 5.12: Examples of available gobo patterns. Patterns such as these can be used very effectively to enhance the appearance of a production.

More complex (and consequently expensive) gobos are available that are made using glass and a photo-etching technique. This can yield photographic quality shaded projections with an extremely high resolution. Some theatre supply houses can even custom-etch patterns from photographs or negatives, though this tends to be expensive.

Generally, gobos are placed in metal gobo holders and inserted into the instrument via a special slot. Sometimes old ellipsoidals do not have provisions for a gobo holder, therefore the gobo must be wedged into the instrument's aperture. This tends not to be optimal, because the lack of an externally accessible holder makes it very difficult to move and adjust the image.

Several companies produce gobos, often times the same companies that sell color media. Catalogs of patterns are available, usually free of charge, from these companies or their distributors.

Figure 5.13: A striking scene from the 1995 WPI Masque production of Ray Bradbury's Fahrenheit 451. The effect was created by projecting a foliage pattern onto a scrim (a large mesh cloth).

Interesting effects can be obtained by combining gobos and multi-colored color gels. Pieces of different color gels can be cut up and taped together to form a single, multi-colored sheet of gel. When combined with a window gobo, an interesting stained glass effect can be had. A similar effect on a larger scale can be had by using multiple instruments, each with their own gobo and gel. Each gobo projection makes up part of a larger pattern. This requires careful focusing, but the end result can be quite impressive. Creative use of gobos and gels can yield some surprisingly good effects, and are among the least expensive things that can be done to improve the look of a production.

In a pinch, custom gobos can be cut out of several layers of black aluminum foil (often known by Rosco's trade name of Cinefoil) using a sharp razor blade. This typically only works for pattern outlines, but some surprisingly good effects can be had with this technique.

next up previous contents index
Next: Dimmers Up: Lighting Previous: Dichroic Color Filters   Contents   Index
Steve Richardson 2000-07-06

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