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# LED Stage Lights

Reduce the wattage and heat of your average stage show
 (+2) [vote for, against]

Cram about 2,000 red, yellow, and blue LEDs into a stage lighting instrument.(Stage light= about 59,000 lumens LED= about 23 lumens). Add a circuit that could be controlled by a light board.

PRO's: Uses less wattage, generates less heat, allows light operator to change the color of light from the board.

CON's: If the light comes from separate LED's, making colors lowers the intensity o the light.

This instrument would be most useful to wash the stage with color, and might be very useful for depicting sunsets over time...

 — dbsousa, Jun 20 2005

The Color Kinetics Colorblast http://www.thelight...m/products/*/*/1506
Will do static colour mixing or chase through the rainbow. [wagster, Jun 20 2005]

Pulsar's led range http://www.pulsarli...com/ChromaRange.htm
Loads 'o the stuff. [wagster, Jun 20 2005]

Lemon Jelly http://www.cdtimes.....php?contentid=1667
Pics of a band who use LEDs on stage. The photos dont do them justice, though. [Stoo, Jun 25 2005]

 The trouble is that light does not add linearly.

 If you combine incoherent light sources, some of the photons constructively interfere and some destructively interfere.

 To find the resulting luminosity of a group of lights, square the luminosity of each light, add them together and take the square root of the sum. If they're all the same you can square one of them and multiply up.

 So, the luminosity of 2000 LEDs is: (2000 x (23^2))^.5 = 1028 lumens

To get 59,000 lumens from 23-lumen LEDs, you need:
(59,000 ^2) / (23^2) = 6.5 million LEDs.
 — st3f, Jun 20 2005

Both figures sound wrong.
 — mensmaximus, Jun 20 2005

The maths might be easier if you restrict yourself to using single photon LEDs.
 — Detly, Jun 20 2005

"Both figures sound wrong."
That's why I did the maths twice. Feel free to check my calculations. In fact, I'd prefer it if you did.
 — st3f, Jun 20 2005

 We have several Color Kinetics LED fixtures in one of our rooms. Each fixture has 96 LEDs in them and while they're useful for washing the walls (the fixtures are hidden behind soffits) I don't think they're nearly bright enough for direct stage use.

 Also, the color values and brightness don't ramp smoothly. You can program them, or control them, to do progessive fades but the steps are discrete and noticeable. They do work well for short duration changes but anything longer than a second or so and the value jumping, or quantizing, looks like a weird flicker and is somewhat annoying. In a theatrical setting, it seems to me, this chunking would be distracting and call a lot of attention to the lighting instrument itself rather than "disappearing" into the scene as it should.

 Now, if you can shutter the LED array with an LCD screen or some other facile device that can selectively and articulately block light you might have something. Imagine you have an LCD screen where, instead of a cold-cathode backlight source, you instead have a very densely packed, and bright, LED array source then you can discretely control both the LEDs for gross luminance shifts while very finely controlling the LCD "shutter" or "gel" for subtle lighting effects. You could even play a video signal through it to add moving light effects.

 Even so, it'll never be a key light but much more a softlight (fill).

My two cents.
 — bristolz, Jun 20 2005

st3f, you mean my 3,000,000 candle power spot light is really not that good?
 — Ling, Jun 20 2005

Shine it into your eyes, and see if the light comes out of your ears.
 — angel, Jun 20 2005

 "st3f, you mean my 3,000,000 candle power spot light is really not that good?"

heh. A 3,000,000 candle power device produces 3,000,000 times as much light as 1 candle, *not* the equivalent light of 3,000,000 candles. It'll be fine for looking around the cupboard under the stairs... possibly without opening the door.
 — st3f, Jun 20 2005

 I have installed many led uplighters and wash lights, both on stage and architecturally. Colourblast make some extremely good ones. The light intensity falls short of what is required for full stage lighting (though this is expected to change over the next few years), and the colour mixing is not perfect, but it is extremely useful nonetheless. We installed a permanent set last christmas which used colour mixing leds and fibre optics powered by colour mixing HMI lamps which allows us to light the set in any combination of two colours - instantly. Very helpful when matching set lighting to powerpoint graphics.

Though I hate to say it, I think this is [m-f-d] - widely known to exist (links).
 — wagster, Jun 20 2005

//it'll never be a key light but much more a softlight (fill)// - you're probably right at that, you can't focus leds. I didn't have any ramping problems with mine though, maybe they've sorted that out now.
 — wagster, Jun 20 2005

 Does the brightness of your individual LED elements ramp or do they merely turn on and off to achieve a given value?

With our Color Kinetics, the LEDs are all fixed brightness and different arrangements are turned on to achieve an overall setting.  It is this switching that makes them stuttery looking.
 — bristolz, Jun 20 2005

 Ah no, the Colorblasters that I have used were all variable brightness, like most modern led lights. The fades were seamless, but the colour mixing wasn't perfectly even because you are trying to mix red, green and blue using leds that are in similar but not identical places.

PS Did you get my email?
 — wagster, Jun 20 2005

Yup, did.
 — bristolz, Jun 20 2005

Ok.
 — wagster, Jun 20 2005

That's what I love about halfbakery. I can find out that my idea can't be done and already exists in the same thread. Thanks for the link, Wagster. I wondered why I hadn't heard of this before...
 — dbsousa, Jun 21 2005

//A 3,000,000 candle power device produces 3,000,000 times as much light as 1 candle, *not* the equivalent light of 3,000,000 candles.// This I do not get. This business about incoherent photons interfering - should this not apply also to photons from a "single" light source? IE, if I have one candle, presumably there are billions of sources of photons (ie, all the tiny carbon particles in the flame or whatever) interfering with eachother. I would have thought that, by this reasoning, you could never have a bright light except for a laser. Not saying you're wrong, I'm just puzzled.
 — Basepair, Jun 21 2005

 "This I do not get." Yeah... it hurts my head, too.

 "...should this not apply also to photons from a "single" light source?" Yes, it's exactly the same principle.

"...by this reasoning, you could never have a bright light except for a laser."
Well, no, but it does help explain why even low power lasers are so bright. A coherent light source has a single wavelength with all the photons in phase and positively reinforcing each other.
 — st3f, Jun 22 2005

 I'd disagree with the 'widely-known' mfd... perhaps to a certain subset of humans, but I'd wager your average joseph hasn't heard of it.

For example, the author, who clearly has an atypical interest in the topic, was not aware of its existence.
 — waugsqueke, Jun 22 2005

As a footnote, I was talking to a lighing designer last night about these things and she told me that there are now led lights that will colour mix using a dichroic prism in much the same way that lcd projectors do. This eliminates the fringing problems that have dogged colorblasts and the like. They still can't be hard focussed though as they still use multiple light sources.
 — wagster, Jun 24 2005

 [st3f] "frequently and spatially coherent" is how I've heard that called.

And, yes, the mfd should probably go.
 — bristolz, Jun 24 2005

 — Thoughtnaper_1, Jun 24 2005

I don't see any evidence of anything other than English on this page other than your oddball cryptic gibberish.
 — bristolz, Jun 25 2005

Even if a single LED is coherent, unless it's somehow coupled to the other hundreds of LEDs required, it won't be coherent with them.
 — Detly, Jun 25 2005

Pa`ve. Careful with the word coherent. If a light emits one wavelength of light only it is monchromatic. If a monochromatic light emits light that all has the same phase then it is coherent. While LEDs are nearly monochromatic, I doubt they provide coherent light for anything more than a couple of millimeters, if at all.
 — st3f, Jun 25 2005

 Is this an instrument like a pipe organ is an instrument, played by an operator, but the output is light not sound? Sounds groovy to me!

Ever heard of a band called Lemon Jelly? They use large banks of LEDs facing the crowd. They display patterns and colours with them, but I think they're pre-programmed, not played live by an operator. (Link added to the link section.)
 — Stoo, Jun 25 2005

Yes but for an entire array of thousands of LEDs to emit light that's all in phase with every other LED requires some sort of mechanism to ensure they start and remain in phase.
 — Detly, Jun 26 2005

Fairy nuff [bris].
 — wagster, Jun 28 2005

?
 — bristolz, Jun 28 2005

 I'm soldering up the bus wires to three rows of RGB on this clear plexiglass one foot diam. spinning disc. Don't have time to calculate the size of the buss wire; that's life, it's large, in kitchen R & D. I'd like to have a hole in the middle of this disc where a camera lens shoots through. The disc could be slightly concave/adjustable and spinning to act as a color selectable 'Obie" light for camera operators.

As it is, this device will be on the other side of the camera, sparking up the visuals, in time to the music for example.
 — mensmaximus, Jun 28 2005

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