Gobo (lighting)
Encyclopedia
A gobo derived from "Go Between" or Goes Before Optics -originally used on film sets, is a physical template slotted inside, or placed in front of, a lighting source, used to control the shape of emitted light.
In the design of an artificial environment in which lighting instruments are used, it is sometimes desirable to manipulate the shape of the light which is cast over a space or object. To do so, a piece of material with patterned holes through which light passes is placed in the beam of light to allow only the desired "shape" or pattern through, while blocking the rest of the light, casting a specific shadow/light into the space.
Though the term "gobo" has come to generally refer to any device which produces patterns of light and shadow or various pieces of equipment that go before a light (such as a gobo arm or gobo head), the specific term itself also defines the device used in theatrical lighting applications because of the mandated placement of the device in 'the gate' or 'point of focus' between the light source and the lens
es (or optics
). This placement is important because it allows the focusing of the pattern or shape into a crisp, sharp edge (for logos, fine detail, architecture, etc.) and also the softening the edges (breakup patterns, etc.). On film sets gobos, also known as Flags and "cookies" which are placed in the beam of light post-optics do not have the option of such fine focus
.
A theatrical gobo may be made from either sheet metal or borosilicate glass, depending upon the complexity of the design.
Glass gobos can include colored areas (much like stained glass
windows), made of multiple layers of dichroic glass, one for each color glued on an aluminium or chrome coated black and white gobo. New technologies make it possible to turn a color photo into a glass gobo.
In low budget theatre, discarded soda cans or pie plates can be used and patterns cut out with any cutting tool. The latest commercial technology enables finely dithered patterns which give the illusion of shading. In the UK, printer's Lithoplate
was widely used as an inexpensive gobo substitute. However, these gobos tend to wear quickly due to the heat produced by a stage lighting instrument
and are not viable for most venues.
Plastic gobos—which are generally custom made—are available 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 to prevent 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 photographic supply companies, or custom gobos from customer-created images can be manufactured for an additional fee. Generally the lighting designer
chooses a pattern from a catalogue or small swatch book provided by the manufacturer. Because of the large number of gobos available, they are generally referred to by number, not name. For example, most manufacturers offer a gobo of a window, but they are all slightly different. So instead of calling it window, it would be identified as gobo 77143 http://www.rosco.com/us/gobocatalog/gobos/pages/77143.html
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The gobo is placed in the focal plane of the lantern
(generally an ellipsoidal reflector spotlight). The gobo 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 dance floor.
Gobos can provide everything from abstract dappled light effects to complex night-time cityscapes. They are commonly used in stage lighting
, television, and film production to create texture, mood, or set a scene. Specialized attachments are available to rotate multiple gobos in different directions and rates to create an illusion
of motion, such as that of light reflected off of moving water.
This effect allows the lighting designer
to produce effects to help portray the scene. For example, a gobo with a cloud pattern may be used to suggest a scene is outdoors.
The support system used to position and hold these flags in the light beam has, as its core component a fully rotatable, adjustable clamp called a gobo head. http://www.matthewsgrip.com/common/image.php?image=349580HappyHead.jpg&width=300&height=326&title=Gobo%20Head Gobo heads are mounted at the top of C-Stands and on the ends of 30" long aluminum bars, called Gobo arms or Grip arms.
Gobos are sometimes, incorrectly, known as "Bogos."
In the design of an artificial environment in which lighting instruments are used, it is sometimes desirable to manipulate the shape of the light which is cast over a space or object. To do so, a piece of material with patterned holes through which light passes is placed in the beam of light to allow only the desired "shape" or pattern through, while blocking the rest of the light, casting a specific shadow/light into the space.
Though the term "gobo" has come to generally refer to any device which produces patterns of light and shadow or various pieces of equipment that go before a light (such as a gobo arm or gobo head), the specific term itself also defines the device used in theatrical lighting applications because of the mandated placement of the device in 'the gate' or 'point of focus' between the light source and the lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
es (or optics
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
). This placement is important because it allows the focusing of the pattern or shape into a crisp, sharp edge (for logos, fine detail, architecture, etc.) and also the softening the edges (breakup patterns, etc.). On film sets gobos, also known as Flags and "cookies" which are placed in the beam of light post-optics do not have the option of such fine focus
Focus (optics)
In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by...
.
Use
Gobos may be used, in connection with projectors and simpler light sources, to create lighting scenes in a theatrical application. 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 or other feature.A theatrical gobo may be made from either sheet metal or borosilicate glass, depending upon the complexity of the design.
Glass gobos can include colored areas (much like stained glass
Stained glass
The term stained glass can refer to coloured glass as a material or to works produced from it. Throughout its thousand-year history, the term has been applied almost exclusively to the windows of churches and other significant buildings...
windows), made of multiple layers of dichroic glass, one for each color glued on an aluminium or chrome coated black and white gobo. New technologies make it possible to turn a color photo into a glass gobo.
In low budget theatre, discarded soda cans or pie plates can be used and patterns cut out with any cutting tool. The latest commercial technology enables finely dithered patterns which give the illusion of shading. In the UK, printer's Lithoplate
Offset printing
Offset printing is a commonly used printing technique in which the inked image is transferred from a plate to a rubber blanket, then to the printing surface...
was widely used as an inexpensive gobo substitute. However, these gobos tend to wear quickly due to the heat produced by a stage lighting instrument
Stage lighting instrument
Stage lighting instruments are used in stage lighting to illuminate theatrical productions, concerts, and other performances taking place in live performance venues. They are also used to light television studios and sound stages.Many stagecraft terms vary between the United States and the United...
and are not viable for most venues.
Plastic gobos—which are generally custom made—are available 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 to prevent 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 photographic supply companies, or custom gobos from customer-created images can be manufactured for an additional fee. Generally the lighting designer
Lighting designer
The role of the lighting designer within theatre is to work with the director, choreographer, set designer, costume designer, and sound designer to create an overall 'look' for the show in response to the text, while keeping in mind issues of visibility, safety and cost...
chooses a pattern from a catalogue or small swatch book provided by the manufacturer. Because of the large number of gobos available, they are generally referred to by number, not name. For example, most manufacturers offer a gobo of a window, but they are all slightly different. So instead of calling it window, it would be identified as gobo 77143 http://www.rosco.com/us/gobocatalog/gobos/pages/77143.html
Mechanics/optics
>
The gobo is placed in the focal plane of the lantern
Stage lighting instrument
Stage lighting instruments are used in stage lighting to illuminate theatrical productions, concerts, and other performances taking place in live performance venues. They are also used to light television studios and sound stages.Many stagecraft terms vary between the United States and the United...
(generally an ellipsoidal reflector spotlight). The gobo 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 dance floor.
Gobos can provide everything from abstract dappled light effects to complex night-time cityscapes. They are commonly used in stage lighting
Stage lighting
Modern stage lighting is a flexible tool in the production of theatre, dance, opera and other performance arts. Several different types of stage lighting instruments are used in the pursuit of the various principles or goals of lighting. Stage lighting has grown considerably in recent years...
, television, and film production to create texture, mood, or set a scene. Specialized attachments are available to rotate multiple gobos in different directions and rates to create an illusion
Illusion
An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. While illusions distort reality, they are generally shared by most people....
of motion, such as that of light reflected off of moving water.
This effect allows the lighting designer
Lighting designer
The role of the lighting designer within theatre is to work with the director, choreographer, set designer, costume designer, and sound designer to create an overall 'look' for the show in response to the text, while keeping in mind issues of visibility, safety and cost...
to produce effects to help portray the scene. For example, a gobo with a cloud pattern may be used to suggest a scene is outdoors.
Common Gobo Sizes
| Letter Size | O.D. (mm) | I.A. (mm) | Notes |
|---|---|---|---|
| C size | 150 | 120 | |
| A Size | 100 | 75 | |
| B Size | 86 | 64.5 | |
| BG Size | 79 | 64.5 | |
| M Size | 66 | 48 | |
| G Size | 65.5 | 48 | For Clay Paky Goldenscans. |
| D Size | 53.3 | 38 | |
| Cyberlight | 44.25 | 38 | |
| E Size | 37.5 | 28 | size t |
| Studio Spot 575 | 36.3 | 31 | For HES Studio Spot 575. |
| Mac 500/918 | 27.5 | 22 | |
| V Size | 25.5 | 22 | |
| Mac 250 | 22.5 | 17 | |
| 518 Size | 20 | 13 | |
| O.D = Outside Diameter; I.A. = Image Area | |||
Other meanings
The derivation "Go-between" is from motion picture production, where gobo is an antiquated term for a what is now called a "flag". Flags are manufactured in a variety of sizes and shapes, are most commonly made of opaque black fabric stretched over a steel frame, but flags can also be made of sheet steel or wood for specialised use. Shaped flags are placed in the beam of a light source in order to create shadows, this type of flag is commonly known as a Gobo.The support system used to position and hold these flags in the light beam has, as its core component a fully rotatable, adjustable clamp called a gobo head. http://www.matthewsgrip.com/common/image.php?image=349580HappyHead.jpg&width=300&height=326&title=Gobo%20Head Gobo heads are mounted at the top of C-Stands and on the ends of 30" long aluminum bars, called Gobo arms or Grip arms.
Gobos are sometimes, incorrectly, known as "Bogos."