LS color mixing?

Has anyone tried color mixing with the luxeon stars? They do make a red green and blue one.... Does it come out reasonably white when diffused? Or does the array have to be set up like the nichia RGB arrays where its 1R, 1G, and 2B, to make up for the lower output of the blue led?

-Dan

Has anyone tried color mixing with the luxeon stars?

Now you`ve got me thinking- the latest product from Color Kinetics perhaps- Luxeon Sauce Light-washers


Seriously,. give me until after dark and I`ll fire up the camera and a couple power supplies and see what we get.

Thats the direction I was thinking in. If colorkinetics had good success with 5mm led groups, then a 6" or 8" fresnel sized fixture might actually approximate the light output of an actual theatrical fixture.

-Dan

In my experience, the red has been the deficient color when using modern, high powered LEDs.

Grab any Color Kinetics fixture and switch it to "white". What you end up with is a lighter shade of cyan or aquamarine instead because there isn't enough red.

Don Klipstein has devised formulae for taking ordinary off-the-shelf LEDs and getting a reasonable approximation of white out of them. You'll see that the red LEDs are the problem, but not in the way you might think.

How Many Red, Green, and Blue LEDs to make White

OK well I`ve been distracted by all the pretty fireworks outside for most of this evening (for`tis Bonfire Night here in the UK) but they`re all but gone now so I`ve now had chance to make some interesting colours myself here inside.

First, the raw materials- Red, Green and Blue Luxeon Star LEDs. The current "batwing" types. For the sake of fairness, and the fact that my main PSU`s all messed up so the current limit doesn`t work right any more, they`re running at 254mA each, connected in series to what`s left of the constant current output.
Also my tripod broke and now it won`t reach up to my main target till I find that pesky roll of Duck tape and fix it, so I`m using my clone of Craig`s target that lives below it. I`ve got just enough component catalogues to prop up that broken leg to the right height, and....

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Taken at slightly different iris settings, so as to show the colour as best I can. No time for color correction as it`s quite late, sorry. But they`re close enough.


Combinations? Well, first thing you`ll note is that the blue overwhelms the others. This is mostly true, the blue LS is the broghtest, followed by Red, then green pulling up the rear. That and the fact that my old VC is most sensitive to blue light (can`t even see IR) and as such, blue flares out brighter than it should.

Here- Red and Blue....
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Red and Green...
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Blue and Green...
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All 3....
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Unfortunately the beams do not overlap too well- each is a slightly different shape. They were all held about 17ins from the target and aligned the best I could. The "white" colour produced by all 3 is less blue than this, more a pinky/violet colour overall, due to the green`s deficiency.

I reckon that Lambertian (the new ones) LEDs, in their naked form, would blend rather more nicely- no rings or hotspots to spoil things, but a wide flood beam instead of a spot. Either that, or a diffusing of these focussed beams (through a material like CK uses in their Sauce LightWasher- to diffuse the light from the 5mm LEDs inside).

Anyway I hope this has helped, and sorry for the poor colour rendering. Assume less emphasis to the blue in reality, though it is still quite potent and ideally needs toning down. Perhaps 250mA through red and blue and 350mA through green? Something I may try in the future when there`s more time.

One final note, I found out while doing those photos, that not only does my current limit adjust not work right, but also the Milliamps range on my nifty new state-of-the art bench meter doesn`t work either.


Too bad- must be a fuse inside or something . Still, those Nixie tubes have more class than the boring (but slightly more interesting thanks to custom white LED backlights) LCD display in the Fluke 8010A.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Stingmon:
In my experience, the red has been the deficient color when using modern, high powered LEDs.<HR></BLOCKQUOTE>

Chris Vernon who made the famous cave light using coloured LEDs, had to change half of the red LEDs to amber ones because his light was to reddish. It was about 3 years ago and he came close to 30lm/W at this time. He designs LED applications as a profession.
Unfortunately I have the data about this light only on paper (and should send copies to one of the CPF members since a month or so....)
The light does a good job for caving, although when you shine it on an even white wall you may see slightly dominating colours in the different parts of the beam.