November 05, 2006
A Geek Tries the Enlux
The lights in my house are always burned out. Even though I buy a whole pile of bulbs every time I go to hardware store, I guess I don't get enough. I am always out.
Last week, the floodlight above my desk went out, and I decided it was time to try something different....
Over the last few years, LED technology has advanced rapidly enough to transform LED flashlights. What started as quirky homebrew hobbyist gadgets quickly became high-performance items for flashaholics; and now, regular consumers can find cheap LED flashlights on the shelves at Sears and Rite-Aid. LEDs continue to get brighter: they are about to make the leap from flashlights to floodlights.
Why switch away from regular light bulbs at home? For me, the main advantage of LEDs is that they essentially never burn out compared to incadescents. Lasting 25 or 50 times longer than a regular bulb, they promise to be "install and forget."
Sure, another advantage of LEDs is that they draw much less electricity than a regular bulb. But the real efficiency benefit is that they run cool. When I put halogens in my attic office, I find I have to stick an extra air conditioner in the window. So LEDs should save a bundle on AC costs. Even though LEDs are expensive, they inhabit the same corner of the manufacturing world as microchips and Moore's law, and they get cheaper and better every year. LED lightbulbs are the wave of the future.
After my office light fizzled, I sat in the dark and thought, "I am ready for the future now."
Trying out Enlux
Some Googling led me to Enlux (they have won awards for their lighting products, and they have been the the subject of stories on BBC and elsewhere). A bulb from Enlux isn't cheap, but I figured it should be interesting. So I sent in my $80 to get one white Enlux R30 Floodlight; it arrived in a nice little box a couple days later, a futuristic device with cooling fins, exactly as advertised. It fit right into the regular light socket, no problems, no worries. When I flipped the light switch, it turned on just like a regular light.
I have been pretty happy working under the Enlux bulb every day. Unlke some of the "45 watt equivalent" bulbs that you can find on ebay - bulbs that are not actually nearly as bright as advertised - the Enlux bulb really is very bright. It is certainly too bright to look at directly; it is probably as bright as the 60 watt floodlights installed next to it on the track, and it is definitely bright enough for daily work.
However, I am not quite ready to replace all my bulbs with Enlux bulbs yet. The problem is not the cost, nor the brightness. The problem is the color. Even though the light given off by the bulb looks perfectly white, the bowl of chili on my desk doesn't look quite right.
What is happening?
Here is a math geek explanation.
A Math Puzzle
Here is a puzzle for you. If AB = AC = 1, how can ABC = 0?
How is this relevant? Because in our case, "A" is the human visual system; "C" is the enlux light, and "B" is a weirdly lit object. The answer to the math question is that you can get weird effects like this easily if A, B, and C are multidimensional, and if B and C sit in a larger space than A. For example, suppose A and B and C are:
A = [1 1 0 0] B =  C =  [0 0 1 1]      
It is easy to work out that both AB and AC are the same [1, 1] result whereas A(B*C) is zero. In the case of color perception, A is not a 4-to-2-dimensional projection, but really an infinity-to-3-dimensional projection (where the three dimensions are red, green and blue). B and C both represent infinite-dimensional spectra. It is easy (or easier) to have the same sort of effect with infinite dimensions.
OK, I am a math geek. What the heck do I mean?
The point is that out of the infinity of different wavelengths, the human visual system can only perceive colors on three dimensions: reddish, greenish, and blueish. Really, there are far more colors than just those three, but our eye can't really tell the difference between, for example, broad white spectrum versus a selective mix of three narrow wavelengths of monochromatic red, green, and blue light. And yet there is a real physical difference. And this difference can bite us when we reflect or filter colors.
Suppose "C" is a combination of three narrow wavelengths of red, green, and blue, and "B" is a mix of a broad spectrum of colors except for the colors picked in C. Our visual system A could perceive C as white when reflected off a white paper, and it could perceive B the same white when seen in the sun. But shine a light C against a surface that reflects color B, and you will get complete blackness.
This is the effect that Sony is using to its advantage with its ChromaVue projection screens. They have invented a dark material that reflects only three specific wavelengths, so when you shine broad-spectrum sunlight at it, it looks pretty dark gray, maybe almost black. But when you shine a specific RGB light at it - light that doesn't look any brighter than sunlight to the eye - the same black screen will shine very bright white.
And this sort of effect - not with white and black, but with reds and yellows - is what I am seeing with the Enlux light. When you shine the Enlux on a white piece of paper, it looks white. But when you illuminate a bowl of chili - normally brown when viewed in sunlight - the chili takes on a glowing neon red color, as if it were flourescing. But it is not flourescing. What is happening is the Enlux light is doing a great job at illuminating the reds in the chili, but not doing a very good job at the yellows, and as a result the chili looks very red.
Before my Enlux experience, I wondered why Philips multicolor LED modules (sold to pros, not screw-in like the Enlux) are sold as "RGBA" - red, green, blue, and amber. But now I think I know why. You can't really get yellow right as a reflected color without actually using a yellow wavelength. Besides the chili, many yellow things in my office, including the surface of my wooden desk, also take on a distinctly reddish-orange hue under the Enlux. And my son thinks the Enlux makes other things look a little too green. The Enlux is a yellow drop-out light that masquerades as a white light to the human eye.
The effect is not too bothersome for work, but I would probably not light up my kitchen with it - it makes some food look a little bit too unusual. I bet the problem could be solved by adding some amber or white LEDs to the Enlux bulb. I will hold off illuminating my house with Enlux until then.
The Enlux At Work
After seeing this minus-yellow effect, I thought it would be interesting to try to capture the Enlux light engine at work photographically. I haven't tried to capture the "flourescing" effect - my camera's own red, green, and blue sensors will just throw things off even more. But it is interesting to just take a picture of the Enlux itself, when turned on.
When the light is off, the little LEDs in the Enlux are colorless and transparent - you cannot see if they are white, red, or whatever. And when the light is on, it is so blindingly bright that your eyes (my eyes anyway) perceive the dozens of little LEDs as all white, each and every single one of them.
But the Enlux brochures explain that the Enlux is actuallly made of separate colored LEDs. So I decided to see if this is actually the case by photographing the turned-on lightbulb directly with a camera with all-manual settings set to the darkest settings my camera can do. Here is a photo of the inside of the Enlux, taken at f/22 for 1/1000 of a second, at ISO 100.
See the individual red green and blue LEDs? It is interesting how many red LEDs they use. It is also interesting to note that there are no amber or white LEDs in the mix.Posted by David at November 5, 2006 04:33 PM
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