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What is a GOBO? 
By John Mitchell


GOBO is a lighting term for a metal or glass template that can be inserted into a focusing fixture to project an image.

The term GOBO literally means, "GOes Before Optics". And, while the history of GOBOs beyond that is fairly insignificant, what is important is whether or not you can or should use one.

Does my fixture focus?

The first question you need to ask is whether you have a focusing fixture. In a typical theatrical application, focusing fixtures are known as ellipsoidal reflector spotlights. Brand names for these fixtures include: Leko, Source Four, Shakespeare, 360Q, ERS, MiniEllips, MicroEllips, . These fixtures are designed to have a "gate" which accepts a pattern holder. It can be found on the top of the fixture just forward of the shutters. If your fixture does not have a gate, most likely you cannot use a GOBO.

Fixtures that cannot accommodate a GOBO: fresnels, par cans, scoops, cyc lights, follow spots, beam projectors, and borderlights.

Why Do I need a GOBO? 

Some lighting designers use GOBOS to project literal images. You will see GOBOS for leaf patterns, window patterns, doorways, graphics (hearts, stars, triangles), and foliage. These images are typically used with a sharp focus to show clearly what the image is.

You can also use GOBOS known as "breakups" for texturing an area. These GOBOS include bubbles, circles, dots, holes, lines, woven patterns, geometric shapes, and foliage. These images are typically used with a soft-edge focus to blur or distort the image.

In retail applications, GOBOS can be used to project literal images, textures, or logos. Many retail stores use a combination of GOBOS and "moving fixtures" to make a store’s logo move from outside of the store to just inside the door. Conversely, a logo may be stationary and use a simpler, less expensive theatrical style fixture.

So, why do I need a GOBO? Well, let’s say for example that you are lighting a show that has several different locations, both indoors and outdoors, and that the director and set designer have opted for a minimalist set. Your challenge as lighting designer is to convey the different locations with light. In addition to the choice of colors, you would be well advised to use GOBOS. You can create a forest (using trees or leaves), a wide open field (using cloud gobos projected onto a cyclorama), a library (using windows), a city street scene (using skylines), a journey into Dante’s Inferno (using flames, and some breakups), and end with a desert island (using palm trees, palm leaves and bamboo). You have moved your actors through all of these locations with the use of color and images, some focused, some not.

But, I have a retail store, why do I need GOBOS?

That’s a good question. Our extensive market research has shown the following characteristics of retail establishments that incorporate image projection: they are perceived as more cutting edge, they attract more traffic, and they succeed!

Can I use image projection for a movie theater? Yes, several movie theaters now use GOBOS to project the theater chain’s logo in front of the facility and use GOBOS above the snack bar to advertise vendors. Guess what? They also CHARGE those vendors for advertising! Your use of GOBOS has just increased your revenue!

Can I use image projection for a car lot? Of course! Advertise year-end sales, special promotions, even projecting an image of salesman of the month!

Any retail establishment, and some that are not thought of as retail, can benefit from additional signage. Especially when that signage is inexpensive, moves, and causes a reaction from prospects.

What type of GOBO do I need? 

That depends on your application.

If you are working in a theater and trying to project a tree, you can pretty well assume that one of the GOBO manufacturers has something that will fit the bill. Rosco, Apollo, and Great American Market publish catalogs of standard GOBOS. For the most part, these are metal GOBOS.

If you are working in a retail environment and need a corporate logo, Coca-Cola let’s say, you need to order a custom GOBO. Typically, there is a "set-up" or "tooling" fee (a charge for artwork preparation), and then a charge for the GOBOS themselves. This can be inexpensive (no color, just text, cut on metal) or relatively expensive (many colors and etched onto glass). A good lighting dealer can offer you guidance here.

If you know that the fixture you are using handles heat pretty well, and you need to have color behind your image, you should definitely examine glass as an option.

If you know that the fixture burns really hot, and the image is just text, go for the metal, and order spares!

What About Intelligent Fixtures? 

The manufacturers of intelligent fixtures have not been kind to those that make GOBOS. There used to be two sizes of GOBOS "A", and "B". These options still exist, but there are now 21 sizes listed in Rosco’s latest Pattern Catalog. Each moving light manufacturer uses a different size (sometimes from model to model), and you need to be sure of two things before ordering a GOBO for your moving fixture:

Does my moving fixture allow me to remove the existing GOBOS and change them? Most of the manufacturers allow you to do this, but there are still fixtures on the market that do not allow for GOBO changes. Pop open your fixture and check it out.

What model fixture do I have? Knowing that you have a Cyberlight is fine, but you should know that Cyberlights are available in CX models (which only take metal GOBOS), and SV versions (which can take metal or glass gobos). If you have questions, you should contact a qualified lighting dealer.

Are There Limits to What Kind of Image I Can Project?

With some limitations, you can project virtually any image. There are intelligent fixtures that will allow you to take a photograph and have it etched on glass for projection. The only real limitation is your imagination.

How Do I Determine The Size of My Gobo?

The manufacturers of Gobos have provided us with a chart that compares sizes and fixtures. For your convenience, you can cross-reference your fixture here.

John Mitchell
Sterling Technical Services
www.LightTrader.com 

 

 

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