A gobo is a thin circular plate with holes cut in it to create patterns of projected light. The name may be derived from a contraction of "go between", or from "Goes Before Optics". " Go Between" means between the lamp and the lens. Another possible origin is from the early days of Hollywood. When the Director of Photography wanted daylight excluded from some area of the set, he'd say "Go Blackout". Members of the crew would run around putting black material between the sun and the set. A gobo may also be referred to as a cookie, flag or cucoloris, possibly from the Latin cucullus for a hood or cowl.

Production

A gobo may be made from thin metal sheet, usually stainless steel or from borosilicate glass with a metal thin film coating, depending upon the complexity of the design.

Glass gobos can include colored areas (much like stained glass windows on a small scale), made of multiple layers of dichroic glass, one for each color glued on an aluminium or chrome coated black and white gobo. New technologies have made it possible to turn a color photo into a glass gobo.

For simple designs needed in a hurry or low budget theater, old soda cans or pie plates can be used and patterns cut out with any handy cutting tool. The latest commercial technology permits very finely dithered patterns that give the illusion of shading. In the UK, Lithoplate, from printers, was widely used as a cheap gobo substitute.

Plastic gobos are also available (generally custom made) when a pattern is needed in color and glass does not suffice. However, these thin plastic films generally need to be used with special cooling elements which keep the heat of the light from melting them. A lapse in the cooling apparatus, even for just a few seconds, can cause an expensive gobo to be ruined.

A number of simple and complex stock patterns are manufactured and sold by various theatrical and photography supply companies, and some suppliers are also willing to produce custom gobos from customer-created patterns for an additional fee.

Use

The gobo is placed in the focal plane of the lantern (generally an ellipsoidal reflector spotlight). The image to be projected is inserted upside-down and back-to-front. The desired pattern is then projected by the lantern onto whatever surface it is pointed at such as a wall or dancefloor.

Gobos can be used to provide everything from abstract dappled light effects to complex night-time cityscapes. They are commonly used in stage lighting or television and film production to create texture, affect mood, or set a scene. Specialized attachments are available that rotate multiple gobos in different directions or at different rates to create an illusion of motion, such as that of light reflected off of moving water.

Other meanings

The term gobo is also used for something that blocks direct light from hitting an undesired area, such as a camera lens where it can cause flare.

Manufacturers

• Goboservice - custom glass gobos
• GOBOLAND - custom and collection glass and steel gobos
• DHA - a wholly owned Rosco company
• Gamproducts, Inc.
• Rosco International
• Apollo Design Technology
• Gobo Man

References

• World Wide Words - Michael Quinion writes about international English from a British viewpoint.

Discussion

• Uk Sound And Lighting Community

Stage terminology | Stage lighting

Gobo | Gobo