Rainbow Effect

msawyer52

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OK, we need to get a rainbow effect on a plain backdrop. As always, way too short of $ and short on light fixtures. All our main Lekos are commited just to light the show. We have some very old HUGE 8" 1000 watt lekos without a pattern slot, several 500 watt fresnels and 2 follow spots. Looking for any suggestions before we start hanging lights. Anyone ever project from a prism before?
 

wolf825

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Can you elaborate on the "rainbow" effect? Is it just a color spectrum you want or is it a pattern as well..? Several colors spread accross the backdrop will give you a multi-color effect..depending on the size would depernd on the number of fixtures needed..fresnels could work just fine. Overlapping at points of primary RGB or even CMY will give you an array of color..

-w
 

Van

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Hmm interesting question. Waiting to hear the answers to Wolfs question prior to submitting a good answer.

Or you could hit the lens on one of those 1k 8" lekos with a crescent, Maybe the cracks would make a prism, Problem solved ! :twisted:
 

Logos

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I got a rainbow effect once by using a 16 lantern Par16 strip light gelled up with the eight ROYGBIV and focused up across the scrim (in this case) to look like the start of a rainbow. It was fairly effective. There must be a way to acheive this cheaply. By the way for violet I used Lee 182 (Congo Blue)
 

gafftapegreenia

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I haven't myself done this myself, but how does more than one gel color work on the same leko? Example: you tape a a red, green and blue together to make 1 piece and put it on one leko. How well would the colors mix?
 

soundlight

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You could make a split gel. Basically, take all of the colors and line them up across the front. You'll have to bargain on the optics lining up properly and being able to give you the soft edge. You could also get a Rosco ImagePro, pop it in a wide-angle leko, and put a rainbow slide in it. Vwahlah! Rainbow! You definitely won't be able to get a sharp focus, though, as that is the one problem with ImagePro units.
 

gafftaper

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If your goal is a full curved rainbow that has all the colors visible, I think your best bet is either buying an I-pro and printing a gobo or getting a custom color gobo done for you. Neither is cheap but you'll get exactly the right look.

Other options like the one above can result in a nice set of striped colors but its going to be really hard to get an actual rainbow shape.

The cheap option and possibly effective one... never tried it, it could work great... Rosco sells a three part gobo set... gel one Red, gel two Yellow, gel three Blue... line them up so they overlap and you've got a rainbow. Unfortunately I it's only a half rainbow. You can find it Here and on the next page of their website. Check Apollo and Gam for multi-part rainbow gobos too they may have other options.
 

gafftaper

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Split Gel is a fun and interesting to play with. I really like to use a yellow and green split gel when I do leaf gobo projections. Yes it's as simple as some gel up and taping it together. I prefer the less popular variety of scotch tape that feels like heavier plastic and looks clear while on the roll for this job (I don't get the kind that looks like a white frost while on the roll but is clear when pressed). You can do a LOT with split gels, it's one of those things that the really creative designers play around with all the time that many people don't even think of (Also try overlapping two gels on at once).

As Soundlight suggested, I think it could work in this situation but that's heavily dependent on the optics of the instrument and again you aren't going to get a nice curved arch look.
 

msawyer52

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Thanks for all the input. We could use either an arched rainbow or a spread spectrum of color, either would satisfy. I found a method using split colors in a large frame and projecting it with a 1K fesnel without the lens and using barn doors to control the spill. It works but your size is limited by the frame and the distance the frame is from the lamp. I've tried some gel slits taped in a frame but the result is really muddy with a fresnel and really crap with a leko. Anyone ever make their own glass gobo using inks? I like the idea of using multiple fresnels with different colors. I just would have to control the spill wuth barn doors, sort of running out of dimmer capacity though. I'll do some more experimenting this week.
 

soundlight

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Aha! The old "fake BP" trick. That's how I think of the fresnel minus lens - an adjustable Beam Projector. Rather nice. Much more spill than a BP, but still - kinda similar. I've used that trick before, although not for this purpose.
 

Van

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Essentially what you've made there is called a Linnebach projector. a great old instrument used to project all sorts of effects in the days before gobos. Typically they look like sort of like an exhaust vent on a roof. Wait I found a picture online..

Good Expirimenting !
 
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gafftapegreenia

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Van, you beat me to it. Theres nothing wrong with reaching into the past to solve todays problems..especially on low budgets... so long as it isn't a health hazard.
 

ship

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The "Go Fres" is of the same concept - only as a patern projector instead of color projector. See USITT 3rd Blennial Theatre Technology Exhibit 1991.

Reflector is removed or covered with black wrap as with the lens.

AT that point, you would if doing some form of colored lens want a safety glass lens or some really high temperature clear plastic - potentially available but not cost effective. Your local glass store could easily knock off some safety glass lenses that would fit into the gel frame of the fixture. Want to gaff tape your lens edges so as to pad them some.

At that point you have a lens, you could dye it as long as the lens is really clean, or possibly just do strips of gel taped to it - outside the fixture side of the glass. This or laminate the gel between two pieces of glass taped together if the glass is cheap enough.

Should work as a concept but you would have to tinker with the beam spread of the Go Fres as opposed to throw direction and distance, and how refined the image would need to be. Some Sharpee lines on the lens between colors could also help refine the rainbow some as a theory to experiment with. Dependant upon how graphic and un-washed out the colors you wished for, you would probably need a few fixtures and they should be as close to as dead on in projecting on the cyc as possible. Angle of projection tends to wash out the graphic rainbow gobo that this would be.

If the image from the Fresnel is not graphic enough, try the fixture in spot position and if still not enough, try the glass lens in a top hat's gel frame holder. All a question of distance and focus verses spill messing up the image.
 

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