A gobo is an object placed inside or in front of a light source to control the shape of the emitted light and its shadow. For studio photography purposes, the term gobo has come to refer to any device that casts a shadow, and various pieces of equipment that go in front of a light (such as a gobo arm or gobo head). In theatrical lighting, however, the term more specifically refers to a device placed in "the gate" or at the "point of focus" between the light source, called a lamp, and the lenses (or other optics).
Derivation The term was originally a shortened version of "Go Between" for Thomas Alva Edison's phonograph recording process as a way to moderate sound levels when recording to wax cylinders. Eventually some of the people who helped the Edison company with recordings also worked in the Edison film studio and put patterns between their new electric lights and scenery while shooting film scenes, and "gobo" was appropriated for lighting since the pattern "goes between" the light and the scenery. It appears to have become standard use in cinema studios in the 1930s. Some lighting professionals believe it is an acronym for "goes before optics" or, less often, "goes between optics". An alternative abbreviation might be "graphical optical black-out". The treatment of the word as an acronym is recent.
Use in studio photography In the photographic industry, a "gobo" describes any opaque, usually black, panel, or "flat", of any dimension, that goes between a light source and photographic subject (such as between sun light and a portrait model) to control the modelling effect of the existing light or, used as a "cutter", to create shadows; or even to control reflections; or between light source and lens, to cut flare. Use of gobos augments light-shaping devices attached to the lights themselves, whether continuous or flash, with cones, snoots, honeycomb grids or barn doors being the most common such fittings.
Subtractive The use of the gobo is "subtractive", as opposed to using a "reflector" to bounce added light into a shadow (thus "additive" lighting). Use of a gobo subtracts light from a portion of an overall shaded subject and creates a contrast between one side of the subject and the other.
Equipment For long shoots on complex sets in the studio more convenient and precise are free-standing boards, often configured as self-supporting hinged door-height panels (usually called "flats"), or if smaller, as a "flag", or a "dot" (a round flag), or a "finger" (larger and rectangular in form) attached to stands, or extending from arms or clamps attached to the tabletop for still-life and product shots. Photographers most often use panels of black foamcore or thick cards. All are devised, or improvised, in different shapes, but are always opaque. The closer the gobo is to the subject, the sharper the shadow. Patent arms with "elbows" that can be oriented in all planes and that can be locked in position are commercially available.
Blocking/reducing light The term is also used for panels or screens used to block light from the lens that would otherwise cause flare or degrade contrast. Such screens as used on films sets may be 3 m (9.8 ft) tall. The photographer on location might use their lens hood, hand or dark slide for such purpose, but with multiple light sources in the studio a range of separate operable gobos provides tailored solutions. A gobo may be used even in the case of broad-source light (a softbox, for example) where the problem is to control reflection in a metallic or glass surface, by placing it in front of the diffuser for a hard-edged dark reflection, or behind, to produce a soft outline.
Use in theatre
Gobos are used with projectors and simpler light sources to create lighting scenes in theatrical applications. Simple gobos, incorporated into automated lighting systems, are popular at nightclubs and other musical venues to create moving shapes. Gobos may also be used for architectural lighting, as well as in interior design, as in projecting a company logo on a wall. Placement in "the gate" or at the "point of focus" is important because it produces a crisp, sharp-edged pattern or design (of logos, fine detail, architecture, etc.). Lighting designers typically use them with stage lighting instruments to manipulate the shape of the light cast over a space or object—for example, to produce a pattern of leaves on a stage floor. Gobos placed after the optics do not produce a finely focused image, and are more precisely called "flags" or "cucoloris" ("cookies").
Use in stage lighting
In DJ lighting, gobos are often combined into a gobo wheel.
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