The word “gobo” originated in the film industry. It's short for “go black out”. When there was a need to quickly completely dim a spot, one just placed a solid metal plate in front of the spot. Soon people noticed that one could project patterns by cutting those patterens out of the plate… the gobo was born. A gobo is either made of very thin stainless steel (metal) or glass.
A metal gobo has a cut out shape/design/patern that when light is shined at it light will pass through the cut out and the shape/design/pattern will be projected. Normally you would then use dichroic filters to get the shape/design/pattern to project in different colurs. Clever design of metal gobos and multi colour dichroic filters (colour wheel)can create some impressive projections. Some metal gobos can be created with dichroic filters on them to produce exactly the colours you want and in the right places. An animation wheel is usually metal and has a pattern cut into it (see the last picture below) these are used to create the water, flame, snow and other effects.
Glass gobos use coloured glass to get the picture/shape/pattern you want, they work in a similar way to metal gobos except where you do not want light projected it is coloured black. Very realistic pictures can be put onto glass gobos to create wonderful projections. The projection can be further enhanced or ruined by the use of dichroic filters.
Gobos are of different size, both physical and projection, and fixing methods if replaceable, are dependent on the fixture and/or manufacturer of the fixture.
Gobos may or may not be replaceable, if they are you can get your own gobos designed/manufactured. If not you might be able to get the whole wheel cut (see the first picture below).
Metal gobos are cheaper to create than glass gobos because it normally just involves laser cutting the required shape out of the thin stainless steel.
If you want to get your own static replaceable gobo, you will need to check the orientation of the replacable gobo to ensure you get it manufactured correctly so when fitted it displays as you want to see it. Remember there are multitudes of ways a fixture can be mounted. What is meant by this for example is a gobo that has a word on it and projects correctly when a scanner is hanging down will mean that if the scanner is mounted the other way around the gobo will be upside down. Some fixtures do not allow fixing the replaceable gobo in any position as they use a key slot.
|Examples of Gobo Wheels|
|Wheel with fixed Metal Gobos||Wheel with Rotating Metal Gobos||Wheel with Rotating Glass Gobos||Gobo Animation Wheel|