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Gobos – A Guide To Choosing And Using A Gobo

The gobo, one of the oldest stage lighting effects, is still one of the best, cheapest and most versatile even today. A gobo is traditionally a piece of metal, with shaped holes cut into it, that produces a pattern of light. The design of the pattern can be anything, from abstract shapes to a sign or logo, and is inserted into a spotlight at the focal centre (known as the “gate“) between the lamp (bulb) and the lenses. This guide to the gobo looks at the types of gobo currently available and gives you some tips on their use.


stage-lighting-gobo
Image by DMBfreakno.41

Types Of Gobo

Metal Gobo – The traditional stage lighting gobo is made from sheet metal that is cut out to produce the gobo pattern. The metal gobo masks out areas of the spotlights beam and are held in place in the spotlight using a gobo holder. Gobo manufacturers are able to cut very intricate designs out of the metal although some areas of a pattern design have to be connected by a small tag. Metal gobos are the cheapest way of producing patterns in stage lighting and, when used well, still look great.

Glass Gobo – These gobos are made from glass with the gobo pattern etched using aluminium or other coating to mask out the light. This means that even more complex images, with no metal tags, can be projected. Glass gobos are fitted in special gobo holders and are extremely fragile. They are only designed to be used facing one way in the spotlight so when you buy one, tell the vendor the make of light so that the image is projected correctly. Glass gobos can crack in use if not heated up gently in the spotlight or if the beam is focussed with a “hot spot” in the centre.

Full Colour and Dichroic Gobos – These gobos are made out of special glass and use a variety of techniques to enable partial colour or even full colour images to be projected. They are quite expensive and fragile so care needs to be taken when using them.

Gobo Designs

Gobos are available in a multitude of stock pattern designs. Some are abstract patterns while others include text, logos and graphic designs. A popular and effective theatre stage lighting effect is to use “break up” gobos, blotchy patterns that produce a random texture of light, and leafy patterns to suggest the light coming through a tree canopy. Other natural gobo designs such as clouds, water and even a moon are useful.

More pictorial gobo designs such as light from windows, street signs and even “happy birthday” (can’t say I have ever used that!) are sometimes required and gobo manufacturers such as DHA or Rosco have a massive stock of gobo designs available “off the shelf”.

Custom Gobos

If you can’t find exactly what you want then you need a custom gobo. A gobo manufacturer will take your design and create one or more gobos to suit you in the size that you require. A custom gobo will cost a good deal more than a gobo from stock and so is probably not suitable for a school play. A large theatre show or corporate event is much more likely to require some kind of custom gobo.

Useful Things You Might Not Know About Gobos

  • When trying to get a gobo image REALLY sharp, try to get the light source as close as possible to 90 degrees to the surface you are projecting onto and use a narrow spotlight.
  • You can improve a blurry gobo image by tweaking the lamp tray of you your spotlight. If you adjust the lamp so it is not so hot in the centre, the image will improve.
  • The wider the angle of your spotlight is, the less chance you have of getting a sharp image all the way across the pattern. Any spot wider that about 30 degrees and you will only ever get one part of the gobo image to sharpen up. 50 degree spotlights are only really good for very arty looking break up gobos.
  • If you are projecting breakup or clouds you won’t care about a sharp image. Focus a zoom profile spotlight as small as you can get away with (this makes sure you get the most light possible out of it) and sharpen the gobo image using the rear lens. When you are happy with the image size, experiment with “blowing” the focus to either side of pin sharp to get your desired look.
  • Break Up gobos and leafy patterns look even better using split colour gels. Use a diagonal 4-way split with two or more colours and experiment with the focus.
  • Fixed (single lens) spotlights will always focus a gobo better than a zoom (two lenses) but you won’t be able to adjust the image size. All zoom profiles have an optimum focal length where your gobo looks really great, often at it’s medium beam angle.
  • If you are having trouble getting a gobo image to sharpen up well, try using a “doughnut”. This is a piece of black alumnium foil (“black wrap”) cut and inserted into a gel frame. Cut a roughly circular hole in the centre about 1/3 the diameter of the spotlight lens and insert the doughnut into the colour runners of the spot. This cuts down some of the lens aberration and helps to sort out the image. It will also cut down your lights intensity a bit but you can always open the hole a bit larger, depending on the focus of your spotlight. In the trade, we often use cardboard dougnuts but we can’t recommend that as they are not flame retardent.
  • When using glass gobos, try not to peak the the lamp with centre hot spot as it can crack the gobo as it heats up. Also, when you dim up a glass gobo for focussing, don’t just stick in at 100%. If you don’t run a glass gobo at full and heat it up gently in should not crack. During your show you can always pre heat the gobo at 20% – 30% just to keep it warm until you need it.
  • If you have ever wondered what the little notches around one side of a metal gobo are, they are for rotational adjustment. The gobo is supposed to be mounted in gobo holder with the notches pointing up to the gate opening. Using a screwdriver it is possible to slightly rotate the gobo in it’s holder for better image alignment. Most stage lighting spolights these days have rotating lens tubes which make this unnecessary.

Good Luck.

Rob

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13 Responses to Gobos – A Guide To Choosing And Using A Gobo

  1. Gary June 10, 2008 at 7:26 am #

    Great article, lots of great information. I just have a few notes, You can buy actual metal donuts for your lights, saves on black wrap and time making them. My company sells them, as well as custom stock steel and glass gobos galore, which are both etched, not cut for finer detail. Here is the link http://www.stagespot.com Custom gobos are only $77 and ship free, most school plays now a days can afford that I believe. Also we never had a glass gobo break in the light do to heating up to fast. We use a much better material to make them now. It might be fun to include why they are called Gobos… Goes Before Optics. If you are looking for more information to add to this you can check out our FAQ on gobos as well http://www.stagespot.com/gobo_info.html

    -Gary

  2. Rob June 14, 2008 at 4:52 pm #

    Hi Gary

    There are a number of theories about where the term “gobo” comes from. No one can seem to agree and I am pretty sceptical about the accuracy of most of them. But thanks for pointing that one out.

    I’m surprised that you have never heard of glass gobos cracking. I worked on a tour where we had about 6 crack on the first show. Luckily, we had spares but taking care of glass gobos, including using the correct gobo holders, is important.

    Thanks for visiting.

  3. karen joyce February 12, 2009 at 11:45 pm #

    Hi can you assist me , I want to use my gogos as scene changes how can I achieve this, would this be a pin wheel effect lighting system .
    this is a great site very informative for the beginner to the knowledgeable

  4. LD SHARUKH February 15, 2009 at 10:52 pm #

    Hi karen
    What are you using to project the gobos.Moving heads, image scanners. Gobo projectors what? There are millions of ways u can do this? Project the gobos onto a large white backdrop and change the gobos from the console. Use several sets of lights for each scene.etc.
    If you tell me what projector u are using i can help…let me know.
    Thanks ciao sharukh

  5. Ray Charnock March 12, 2009 at 12:06 am #

    Thank you for sharing your expert knowledge in such a friendly and easy to understand way.
    We are an established showgroup, performing in different venues, most of which have some lighting and sound consoles, although we do carry our own sound desk, stage lihts and follow spots. We are always looking for ways to improve our presentation and I am wondering whether we can incorporate Gobos into our follow spots. Is there such a thing as an “adapter box” that can be fixed to a spotlight that would accept Gobos?
    Presumably there must be a limit to what can be projected using a Gobo due to their physical size and the “readability” of what you are trying to project?
    Regards
    Ray

  6. Rob Sayer March 12, 2009 at 1:52 pm #

    Hi Ray. Many followspots have an accessory slot in the “gate” (the focal centre) and you can get gobo holders to fit them, along with masks, shutters and other beam shaping stuff. If a gobo holder isn’t available, it wouldn’t be impossible to make one.

    Metal gobos have image limitations but etched glass and full colour / dichroics etc mean that there aren’t many limits nowadays. Don’t forget that even a high quality stage spotlight doesn’t have the optics of a dedicated projector.

    Glad you enjoy the site. Thanks for visiting.

  7. doctorstar December 31, 2009 at 11:45 pm #

    Hi Rob,

    I would like to use split colour gels on a forthcoming production…having not done so before(!)
    Should I tape the diagonal joins and if so, what with? Gut instinct tells me sellotape might be a bit melty in the gaze of a profile spot.

    BW for the new year and keep up the good work,

    Ian

  8. Rob Sayer January 1, 2010 at 9:40 am #

    Hi Ian,

    For gel splits, Sellotape does “bed down” (ie melt) nicely after being heated up but it seems pretty flame retardent and it’s what we generally use. I’ve not had any problems with it, although I suppose the belt and braces answer would be to say scroller tape – the kind used to make up gel strings.

    I love split gels, especially with gobos and Gam Online has a great page on the subject with some design ideas that you may not have considered. Check it out, if you haven’t already.

  9. Derek Gutteridge June 20, 2010 at 10:06 pm #

    Hi Rob
    great article.
    I am staging a show at a church and want to achieve amoving water reflection for some scenes.
    Any advice would be useful.
    I have limited power supply and, hence, limited no of lanterns/channels in use at one time.
    regards

    Derek

  10. Steve Gray December 30, 2011 at 10:06 am #

    In the article about gobos there is no mention as to why there are A and B size gobos for the same lamps. The B size has a smaller grahical space(image diameter),useful for keeping an even focus, this is the type of gobo size that should be used when you want to project company logos for fussy clients. This has the drawback that the image projected will not be as big as the beamspread stated in the technical manuals of the spotlight. The A size gobo is good for breakup gobos.
    Happy focusing…

  11. Patty Perry July 24, 2015 at 5:42 pm #

    Can gobos be re-used? Do they degenerate over time?

  12. Raul ML January 26, 2017 at 6:02 pm #

    Hi!!

    How many gobos would you use in a ML busking show? And what kind of gobos?

  13. Rob Sayer January 26, 2017 at 7:35 pm #

    For me, it’s a couple of beam splitters and something that rotates well in the air. That’s all.

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