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Education Toys Technology

MIT Student Gets Artistic With LED Art 163

Posted by Zonk from the what-are-they-teaching-those-kids-up-there dept.
Gibbs-Duhem writes "An MIT graduate student has up a page showcasing a standout art project. He's designed custom LED light fixtures which are seven times brighter than the closest similar commercial models, and include colors which can't be reproduced by a normal RGB cluster (including two ridiculously bright UV LEDs). The result: some beautiful mixed media artwork. The author's goal is to eventually publish a guide to make getting into creating such artwork more accessible to the general public. The site includes lots of great photos and a movie of the art in action. It also has in depth descriptions of the theory involved in this relatively new form of art, an explanation of how the paints were chosen, and an in depth technical discussion of how such lights are designed with schematics and board layouts for those who might wish to build their own lights."
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MIT Student Gets Artistic With LED Art More

MIT Student Gets Artistic With LED Art

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  • LED art (Score:5, Funny)

    by saskboy ( 600063 ) on Monday March 17, 2008 @12:47AM (#22770554) Homepage Journal
    I've thought for a while that there are great possibilities for LED art. One project I'm not ambitious enough to set out to complete, would be a country's flag, arranged like lite-brites into the recognizable pattern and colours. The whole thing would be powered by a tiny windmill, making it a wind powered flag.

    • Re: (Score:2)

      by xaxa ( 988988 )
      There's some real CFL art [dezeen.com] that's much more impressive than this LED art. (For those who don't want to click, it's CFLs, but the tubes aren't compact, but big and swirly and pretty. I'll go back to my psychoactive drugs now, thanks :-)

  • damnit (Score:5, Funny)

    by MOMOCROME ( 207697 ) <momocrome@gm[ ].com ['ail' in gap]> on Monday March 17, 2008 @12:51AM (#22770566)
    I misread it as "MIT Student Gets Arrested With LED Art" which is of course very exciting as it suggests LED Art is now illegal in Mass.

    It's strange to feel all deflated by reading about a cool and hackish thing like that.

    • Re: (Score:2, Informative)

      by Anonymous Coward

      Getting there. [cnn.com]

      • Re: (Score:2)

        by terrymr ( 316118 )
        Theres this one too [boston.com].

    • Re: (Score:2)

      by Aerion ( 705544 )

      I misread it as "MIT Student Gets Arrested With LED Art" which is of course very exciting as it suggests LED Art is now illegal in Mass.


      No, that really did happen. Seriously. [boston.com]
      • ...Although, if the reporting is accurate and she did indeed try to walk through a security checkpoint, wearing a bundle of wires and circuitry on her chest without responding to security personnel when they asked what the thing on her shirt was, the blame for that incident lies squarely on the MIT student's shoulders.

        • Re:damnit (Score:5, Insightful)

          by Anonymous Coward on Monday March 17, 2008 @05:27AM (#22771552)

          Although, if the reporting is accurate and she did indeed try to walk through a security checkpoint, wearing a bundle of wires and circuitry on her chest without responding to security personnel when they asked what the thing on her shirt was, the blame for that incident lies squarely on the MIT student's shoulders.
          While the reporting was heinously distortive, it was never quite as wrong as you got it.

          Not even faux news said she tried to walk through a "security checkpoint" - all she did was ask a question of the person at the info desk.

          The person at the info desk - NOT EVEN VAGUELY SECURITY PERSONNEL - asked her what the LEDS were, she said "art" and then continued about her business.

          The blame lies solely on stupid CYA security policies that require a "response no matter what" -- that's escalation without application of rational thinking. You've got one dumb cluck of a info-desk clerk, who probably doesn't even have a high school diploma, causing a major incident that could have been easily avoided if anyone at any step of the way had applied a degree of critical thought to the issue. What's next? Exvacutation because someone dreams about a bomb? [guardian.co.uk]

          Don't think for a minute that any of this anti-terrorism "security" is about protecting anyone from actual threats. They might as well name them the Department of the CYA because their sole purpose is to protect the asses of the people in charge. If they react completely out of proportion to any perceived threat, then when an actual threat slips through they can point at all of their over-the-top reactions in the past as proof of 'diligence' thus insuring their asses are well covered, and may even get increased funding...

          This institutionalized cowardice is destroying our country, it has got to stop or we will never be able to maintain our status as the largest superpower.

          • the reporting was heinously distortive

            I feel this bit bears repeating. In both the "Mooninite scare" and the Star thing, one very disturbing aspect of all the local reporting was that it was very heavily spun in favor of the city, the TSA, etc. Referring to a pack of D cells and some LEDs as a "Hoax Device" - even when it was already damned obvious that the Mooninites were neither bombs nor hoax bombs - is just a cheap tactic to make people side with the authorities, despite little matters like common sen

      • What happened to her (Star Simpson)?

        No news of conviction, sentence or acquittal or much of anything?

        Did she "disappear"?

        As controversial as her actions were (*), the fact that there is not even a wikipedia article on her is shocking...

        (*) People saying everything from she should've been shot, should go to jail for the full 5 years all the way towards making her out to be totally innocent of anything, including being a bonehead.

    • Re: (Score:2)

      by flajann ( 658201 )
      Oh you mean: Star Simpson's Big Wrong [urlbit.us]?


      Not that LED Art (and advertisements, if you recall the other idiot overreaction to the LED ads in Boston) is "illegal", but...

      Any sufficiently advanced technology is indistinguishable from a BOMB to Mass Holes!


      Well, now I've said it.

  • It's a nice project, but... (Score:5, Funny)

    by megaditto ( 982598 ) on Monday March 17, 2008 @12:53AM (#22770576)
    It's a real shame they don't make LEDs that emit UV-C. Those would be much better at burning retinas and giving people skin cancer.

  • Don't forget to wear sunglasses. (Score:5, Informative)

    by cjdavis ( 13840 ) on Monday March 17, 2008 @12:57AM (#22770590)
    Doesn't UV cause cataracts?

    Ah yes, from the article:

    As a word of warning, the NCSU034A LEDs output over 300mW of UV light at 385nm! This is a LOT! What makes them especially dangerous is that the die is only a millimeter or two on a side, so the angular intensity of the light is extremely high. Do *NOT* turn these on in an environment where anyone can look directly at them. They are extremely dangerous to the eye, and you will have a *permanent* blind spot if you look directly at them. To make them safe, I used polyethylene plastic sandwiching a Luminit Holographic Light Shaping Diffuser (LSD... yeah, I know, they came up with the acronym first) an inch and a half away from the board to make the apparent source size over an inch in diameter. This decreases the angular intensity from the class 3b level to the class 1 level. I am not liable if you blind yourself by using these LEDs! Seriously, don't fuck around with these.

    Funny story that. Every time I tell an MIT student that the UV LEDs will permanently blind them if they remove the cover, the response is the same. First, they say "Really?", and then they attempt to look into the endcap. True story. Explains a lot, I think.

    • Re: (Score:1, Redundant)

      by Gideon Fubar ( 833343 )
      Goddamn it.. you beat me to it!

      pardon me while i prepare for my (-1) Redundant..

      • Re: (Score:1)

        by cjdavis ( 13840 )
        Well, it appears megaditto beat me, but that's only because I was off looking for references, I swear.

    • Re:Don't forget to wear sunglasses. (Score:5, Interesting)

      by ardle ( 523599 ) on Monday March 17, 2008 @01:19AM (#22770660)
      I got quite bad eye-burn from a UV spotlight (was standing about 2 metres from it for about 2 hours): not a nice experience.
      Didn't notice any effect until about the following evening (thought something was in my eye). I woke in the middle of that night with stabbing pains in my eyes. Next day, daylight hurt my eyes. I couldn't even look at the flame of a candle. Thankfully, eye ointment soothed it and the problem eased the next day (disappeared over the next two or three).
      Doctor couldn't figure out what had happned to me - I only figured it out (after the visit) cos the weather was cold and relief of cold breeze on my face made me realise I had got sunburnt!
      • Yes, this is well known to anyone who've been skiing cross-country at the time of year when the sun gets stronger, especially if you are on large expanses of snow. Your retinas got sunburnt.
        In my language we call it "being sun-blinded". The symptoms are exactly as you describe them.
        I'm surprised that your physician didn't recognise them for what they were. On the other hand, there is no cure except for ointments that give relief, so he got that part right :)

    • Re:Don't forget to wear sunglasses. (Score:4, Insightful)

      by dattaway ( 3088 ) on Monday March 17, 2008 @01:31AM (#22770692) Homepage Journal
      I brought a homemade 250mW laser to work one day. I warned everyone exactly what it could do. What is the FIRST thing each guy did? Try to aim it in each other's faces. True. Lights are like toys and turns people into kids. Get ready to grab it out of their hands.

      • Re: (Score:2, Insightful)

        by Translation Error ( 1176675 )
        It's even worse with a neuralizer. At least with a laser, they'll stop once they injure someone. With a neuralizer, you warn, "Remember what happened last time," and they just look at you blankly before setting it off again.

        P.S. Be really sure you don't forget to wear sunglasses when you bring one of these into work.

      • Re: (Score:2)

        by saskboy ( 600063 )
        Not much pisses me off more than a fool with a laser pointer thinking it's a toy. If blindness were a game, would the game end when someone gained an eye?
      • You cried wolf. Again. They don't know anything about luminous intensity, and the fact that you were packing something that strong never occurred to them.

        They've slapped dire warning labels on 0.1-5mw LEDs that are demonstrably safe to shine directly into your eye for so long, no layperson believes them anymore. Even at/above the upper end of that if you manage to cause serious damage, it's nearly indetectable because the eye compensates so well.

        If you want to warn someone that your machine can cause ocu

    • Re: (Score:2, Funny)

      by Anonymous Coward
      I watched the video from the site and now I have three dead pixels in my left eye. Thanks a lot, Brian!

      You succeeded where Goatse failed.
    • Maybe I'm missing something here, but what is the point of using UV leds? Is it not called Ultra Violet because its above the spectrum of visible light?

      • Re: (Score:2)

        by xaxa ( 988988 )
        I haven't read the article, but perhaps there are UV-reactive materials being lit up, which produces colours not normally available to the artist.
      • The paintings have fluorescent paint in them. It's pretty cool looking to have bright red light at the same time that your fluorescent paints are glowing -- very wild.

  • Art with LED (Score:4, Informative)

    by GregPK ( 991973 ) on Monday March 17, 2008 @12:58AM (#22770594)
    The Mona Lisa is lit up with LED's Buckingham Palace is converting over to all LED lighting http://www.flickr.com/photos/lastboltnut/1466712839/ [flickr.com]. Many cities around the world are converting to LED lighting. It is really quite spectacular transformation of lighting in the world.

    I expect to see 90 percent of lighting changed over to LED lighting by 2015...
    • CFLs for indoors (and certain inclosed fixtures outdoors) will continue to be the norm in energy efficiency. Metal Halide light outdoors (available at Lowes, but not Home Depot, last I checked) make good outdoor driveway lights and the light with much better color rendering than the old sodium light and excellent energy efficiency as well. It would be nice to get LEDS, no doubt, but the lumens output and price just ain't there yet. Hopefully these type of developments will change that.

      While all the hoopl

      • Re: (Score:2)

        by GregPK ( 991973 )
        http://www.leonardo-energy.org/drupal/node/809 [leonardo-energy.org]

        Article mentions this PDF http://www.netl.doe.gov/ssl/workshop/Report%20led%20November%202002a_1.pdf [doe.gov] from the DOE that outlines LED technology Roadmap putting LEDs at the same price of CFL lighting by 2012. Currently, LED technology is already ahead of the roadmap. www.LEDSmagazine.com

        Also, in commercial spaces as it stands today. LED actually pays out in the long-term(5-10 years) when you factor in the cost of replacing the bulbs every few years. Even bette

        • Re: (Score:2)

          by kesuki ( 321456 )
          LEDs are good for the environment in many ways... for one thing they've been catching on as 'Christmas lights' for decoration use the plus side, they can blink a trillion times and never burn out. the downside, you need more sophisticated controls to make sure people can see the blinking. this will undoubtedly save a lot of 'wasted' resource by allowing Christmas decorations to be used for decades, instead of fiddling with bulbs every year to find the shorted ones, or 'just buying new ones' to avoid that
    • A lot [Like the Louvre, British Museum etc] seem to be converting to fiber optics as well. Creates a lovely fill, and also really nice overlapping umbras..

    • Re:Art with LED (Score:4, Interesting)

      by Peeet ( 730301 ) on Monday March 17, 2008 @03:21AM (#22771030)
      Well, speaking from the event production industry (lighting for theatre, film, concerts and conventions) I don't see it coming that quickly. There are ways for LEDs to take over this industry, but they all depend on some other technology or innovation happening first. LED based fixtures are starting to be used as a tool, but they are in their own category, not as a replacement for an already existing tool. The problems that LEDs have are their color rendering index, their lack of brightness and the inability to dim them via the equipment currently used in almost every theater and production company in the industry (dimmers, PARs and Ellipsoidals). Color rendering is being addressed in the same manner as this MIT student (Selador's x7 series [selador.net] uses 7 different color LEDs to expand their palette) and brightness is fast becoming a non-issue as 3 watt LEDs are becoming commonplace. But dimming is the deal breaker as the industry is saturated with SCR based dimmers that control a majority of the conventional lighting fixtures by way of dimming their main AC input.

      For LEDs to be viable, they would have to be able to replace the HPL lamp that is used by the defacto industry standard lighting fixtures: ETC's Source Four [etcconnect.com] PARs and Ellipsoidals. These "conventional" lights plug into distribution cabling that goes directly back to a dimmer rack of some sort where the AC voltage is varied by way of using an SCR to chop the AC waveform at various points thus varying the voltage output and dimming the incandescent lamp. LEDs use DC power and are dimmed by flashing them on and off very quickly (at a constant voltage) and varying the amount of time that they are on versus off to create the illusion of dimming. If you were to put an LED controller onto a dimmed AC circuit, it would fry the controller much the same way that an electric motor would get fried if it were on a dimmed circuit. Sine Wave dimming (new technology) may change this, but that needs to happen first and LEDs second.

      There other ins for LEDs to take over this industry. The other half of the lighting industry (seen more in concerts and conventions and less in theatre and film) is moving lights [wikipedia.org]. They mostly use arc based light sources and are dimmed by way of a motorized shutter blocking the light coming out of the fixture. The power input for these types of fixtures is then run separately straight from the power source and not from a dimmer (just like current LED fixtures). They are very bright and have a slightly colder color temperature and lower color rendering index (also similar to LED fixtures). LEDs would be a perfect fit for moving lights and it is only a matter of time before we see new fixtures being developed with clusters of LEDs powering them rather than an arc lamp. The only problem with this is that it is hard to make optics that will still focus sharp with a source that has multiple points of origination.

      The final point I will make addresses this problem, I believe. Once you start seeing high powered video projectors running off of LEDs rather than arc lamps (as most are now) then there will be no excuse for LEDs not to take hold of the lighting industry as we are also experiencing another revolution where traditional moving lights whose beams are shaped and colored by metal patterns and glass color filters that are mechanically placed in front of the beam inside the fixture are being replaced by essentially video projectors on moving yokes that project all of the colors and patterns by way of a computer video output. Once video projectors have been taken over by LEDs, THEN I predict, at least in this industry, we will start to see some tool replacement rather than just toolbox supplement.

      • Re: (Score:2)

        by GregPK ( 991973 )
        CRI is pretty much a non-issue already. See Mona Lisa... They use a mix of LED colors to get whatever color they want. They can actually get a higher color rendering index than incandescent with LED lighting. Without the Fading, and Infrared that standard lighting setups put out.

        As for the dimming effect I think you could possibly put an LCD over the LED and dim it out with that connected to a controller to output whatever pattern or color you want.

        I don't really see production lighting as all that expen

        • Re: (Score:2)

          by xaxa ( 988988 )
          I dunno... for the Lord of the Rings play at a theatre in the West End, London (UK) they had to put generators outside the back of the building to provide extra power for the lighting effects required -- the normal (for a theatre) power wasn't sufficient! Since a house here gets a maximum of 11-22kW (50-100A×230V) and I expect a theatre gets a fair chunk more than that, that's a decent expense. Worth reducing, anyway.

          P.S. sometimes I go to a nightclub at a weekend and stay for longer than I was at wo

      • Re: (Score:2)

        by xaxa ( 988988 )
        Moving lights are used loads in concerts and nightclubs in London (UK). About the only place I can think of that doesn't have any has a really low ceiling (as in, "don't jump!" low). I don't pay much attention, but places like the couple of student union clubs I go to have almost entirely this lighting, with larger venues having maybe half their lights of the standard type.

        I've seen LED lights used a little at at small venues and at really large concerts, but not at anything in between. I was told that a

    • I expect to see 90 percent of lighting changed over to LED lighting by 2015...
      I don't. In commercial and public settings, maybe. Not in homes, though. People are too used to the way incandescent bulbs look. A room feels very different when lit by a white LED instead of the yellowish tone of incandescents - and not in a good way.

    • Re: (Score:2)

      by Alioth ( 221270 )
      I'd be surprised. Sodium lights are still by far the most efficient light source we have - so far ahead of semiconductor lights in efficiency, it's not even funny. LEDs have a long way to go to match the brightness and efficiency of sodium street lighting.

  • Every time I tell an MIT student that the UV LEDs will permanently blind them if they remove the cover, the response is the same. First, they say "Really?", and then they attempt to look into the endcap. True story. Explains a lot, I think.
    • This is how it is with physicists and engineers, since Galileo damaged his sight looking through his telescope.

      Remember the guys on the Los Alamos project who thought it was cool to have a lump of gold plated plutonium on a stand so you could feel how warm it was? And then there was the scientist I once had the pleasure of working with who thought it was clever to have his 5kV capacitor bank with the live prongs exposed and joined by a copper rod, though the CEO did get pushed out of the way before he could

  • Art? (Score:1)

    by unbug ( 1188963 )
    Whatever happened to the difference between art and design?
    • Oh, it's the usual - outsiders desperately trying to get the coveted label of 'artist' even though most of them will spend their careers designing circuit boards or some other banal horror. Let's just say that this student won't be getting profiled in The New Yorker anytime soon.

  • Fascinating (Score:5, Interesting)

    by djlemma ( 1053860 ) on Monday March 17, 2008 @01:11AM (#22770646)
    I haven't read the whole article, but anything having to do with LED technology is interesting to me. It's interesting, though, that the author doesn't seem to understand color mixing in pigment vs. light.

    He says-
    "You mix red paint and green light, you get what appears to be yellow light."

    That's not true. If you mix red LIGHT and green light, you get what looks like yellow light. If you shine green light on red paint you get a ugly dark mess. The red paint doesn't reflect the green light very well- the reason it's red is because it reflects the red portion of the spectrum. So, when you light it with green, the light that's reflected off the red is not going to be very intense, it certainly won't be yellow.

    Also important is the fact that green is a primary color in light, while yellow is a primary color in pigment. If you shine green light on yellow paint, you'll actually reflect a lot of green, and if you shine yellow light on green paint it'll also (you guessed it) reflect lots of green.

    I think it's interesting that he's finding out how the horrible color rendition capabilities of LED's can be used to one's advantage, but I don't know if he really understands all the theory involved...

    • Re:Fascinating (Score:5, Informative)

      by batkiwi ( 137781 ) on Monday March 17, 2008 @02:34AM (#22770850)
      He gets it but just has a bit of a typo. If you read the rest of that paragraph it's obvious he meant "You mix red light and green light, you get what appears to be yellow light."

      I say this because he later remarks on:
      -"You may think you're seeing yellow light, but the fact is that you are seeing independent red and green light, and your brain is converting that information into the appearance of yellow"
      -pointing a "yellow" LED at "yellow" paint (black!!)
      -pointing an "orange" LED at "orange" paint made by mixing yellow and red paints (red!!)
      etc

      Don't crucify him for just one word mixed up.

      • Nah, djiwhatsit is right, I was wrong. Yellow pigment absorbs blue light strongly, so it should reflect both green and red fairly well and appear yellow. Thanks for pointing it out, I'll correct it and try to come up with a better way to explain it to a relatively non-technical audience. Examples with this sort of thing are fairly hard to come by, and will take some time to fine tune.

        The idea I was trying to get across is that dichromates do not appear as you would expect when they are shone on absorbing

        • Sorry, I take it back. You're right as long as your primary absorbing colors are only Red, Cyan, and Yellow. It really boils down to the absorption spectra of the pigment materials. If I have a pigment that is a "true" yellow (reflects in the yellow, absorbs everywhere else -- including red, green, and blue), than it will absolutely appear to be black if you shine red+green LED light on it. You had me confused for a second, but I see where the misunderstanding is now. This is the entire reason we had to spe

  • the results properly on your plain old RGB monitor / LCD.

  • Meh (Score:5, Funny)

    by timeOday ( 582209 ) on Monday March 17, 2008 @01:18AM (#22770656)
    What's the big deal with this "can't be reproduced by a normal RGB cluster"? All the colors in the screenshots look pretty normal to me, nothing out of the regular gamut. Just like all these suckers and their (so-called) "high-def" TVs, which I've seen in many commercials yet none showing a better picture than the fine Trinitron I already have. Nothing to see here...

    • Re: (Score:1)

      by Scaba ( 183684 )

      I'm guessing you're trying to be funny? Don't think you're having much success...

    • Re: (Score:2, Funny)

      by LunarCrisis ( 966179 )

      What's the big deal with this "can't be reproduced by a normal RGB cluster"? All the colors in the screenshots look pretty normal to me, nothing out of the regular gamut.
      Damn, I followed this article's link from my feed reader to make that very joke, but now that I'm here I see that you've already done a fine job of bungling it...
    • For those of you who don't get the joke, JPEGs (standard ones, at least) use RGB color mixing, along with your monitor, so it won't look any different to you.

      That said, this "discovery" is hardly a new one, as the professional lighting industry use CMY subtractive color mixing almost exclusively. When you're layering multiple gels [wikipedia.org] on top of each other, only subtractive color models work properly.

      However, since this guy is using additive mixing (eg. a discrete light source for each color), his choice of CM
  • There was an LED art installation. It consisted of pretty large array of rgb leds arranged into cube. The LEDs were housed in what looked like ping pong balls or something to this effect. The effects it could produce were phenomenal. The switching was obviously extremely configurable as they were able to amazing shows. Imagine seeing shapes created by these leds moving in any directions (migrating to different leds obviously), changing colours etc. Could only find this video of it. Would have been be
    • See, that reads more to me as "LED Art" than what the author of the article was trying to do. Basically, the article was just explaining how to build your own version of a readily available type of luminaire. The only thing he seems to think is innovative about his is the inclusion of high-power UV LED's. Well, that's cool, and I hope ColorKinetics [colorkinetics.com] (or some other manufacturer of LED lighting) picks up on that idea if they haven't already.. but there's really nothing particularly artistic about the projec

      • I love that piece, they had it set up at burning man this last year too. It really was stunning. I also agree that it's more appropriately called "LED Art" than what we did... the artistic part of what we did wasn't building the light, it was the paintings we made to work with it. Most mixed-media artists don't have the EE expertise to do it on their own, and I sure don't have the painting expertise to do it on my own. The goal of this article is to eventually create a howto so that artists will know exactl

  • A very, very cool project. I wonder if a similar project could produce colored lighting for artistic photography. Heh, by the scan of the schematic, it looks like he's using EAGLE [cadsoft.de] for his PCB design. EAGLE is a very good program.
  • Didn't some MIT idiot pushed her way past aitport security with LED-lightwork and an exposed circuit board less than a year ago? I'm too lazy to google it (I'm can't be bothered to fact check when posting to /.), but the incident stands out in memory.
  • The pic with the 2-tone room (red half, green half) makes me want to convert mine. Anyone know where people can buy colored LED lighting for @home, indoor application? I've not had a lot of success searching in the past.

    • Color Kinetics (now Phillips) is the standard for RGB lighting fixtures. They're just expensive. If you want to buy the lights I made in the article, I'm up for making some custom fixtures that are a bit nicer on the hardware end than the CK ones, but not quite as polished from a software standpoint. Certainly they'd work fine for just cycling through the rainbow in circles endlessly, and I'm setting it up to be designed for permanent installations (a hole in the back to just mount the light on a wall). Sen

  • Worst. Explanation. Evar. (Score:4, Insightful)

    by Alex Belits ( 437 ) * on Monday March 17, 2008 @02:20AM (#22770816) Homepage

    Theory

    The first step of the project was to understand the underlying physics behind LED based artwork. Fundamentally, the eyes are a very odd sensing system. The ears do a frequency based analysis of incoming pressure waves, and report all of the dominant frequencies to the brain for interpretation --- if we hear two frequencies of different pitches, they sound distinct. This isn't quite as true when you talk about harmonics of sounds, as they will start to affect the timbre instead of sounding as a distinct pitch, but the basic idea is that we can pick out independent sounds with different pitches fairly easily.

    The eyes, on the other hand, do spatial and frequency-based sensing; however, they throw away much of the information about the specific frequencies detected. For instance, if you look at any particular spot, you will see a single color -- not a spectral map of the complete visible spectrum coming from that point. This is great for the purposes of vision; it would be rather difficult, I think, to walk around while receiving that much information. However, this means that the eye behaves very strangely in the presence of multiple colors from the same location.

    The classical example of this effect is the color wheel. You mix red paint and green light, you get what appears to be yellow light. But how is this possible? If yellow is a frequency of light, how does mixing red (620nm) and green (530nm) produce yellow (590nm) light? There is certainly no physical process that does this sort of mixing in general.

    In fact, the idea that red and green combine to form yellow is a trick of the mind only. You may think you're seeing yellow light, but the fact is that you are seeing independent red and green light, and your brain is converting that information into the appearance of yellow! Very strange. So, this can explain how a RGB cluster of LEDs can produce most colors of light -- they aren't actually producing those other frequencies of light; instead they are tricking the eyes into thinking that they are producing those other frequencies of light. This trick is summed up in the Chromaticity Diagram (pulled from wikipedia). On this diagram, pure frequencies are displayed along the outer border from 460 to 700nm. As you mix two colors together, you draw a line between their positions on the border, and the ratio of the two tells you the position in the diagram that your apparent color lies. For example, if you combine 520nm green light with 620nm red light in a 50-50 ratio, you will have what appears to be yellow light. Likewise, if you have 620nm red light and 490nm cyan light in a 50-50 ratio, you will have what appears to be approximately white light.

    I have never seen a worse explanation of color vision.

    It would be sufficient to say this:

    Human eyes' colored light sensors cover wide ranges of wavelengths with maximums at red, white and blue, so they can easily see colors of mixed paints (also wide ranges of wavelengths with multiple maximums) and have those colors imitated by LED screens and lights (three very NARROW ranges of frequencies near the maximums of eye sensors' sensitivity) however mixing the two (light from three narrow-band sources is reflected by wide-band paint, then seen by three types of wide-band sensors) produces distorted results because paint's reflectivity of wavelengths outside the lights' narrow bands does not contribute to the impression.

    A paint with one of the narrow maximums at, say, cyan, will appear the same as paint without such a maximum if illuminated by a LED light that produces nothing in cyan range where the maximum is present. It's important to mention that in a photo taken under natural light and displayed on a LED screen, paints' colors will appear perfectly normal. This happens because light and camera's sensors cover approximately the same ranges as human eyes' sensors, so for the area covered with paint that has cyan maximum, screen would produce more green and blue light to imitate the impression on

    • Hiya, I like the way you explain the behaviour of the light, and if you give me permission, would like to adapt parts of your explanation to improve the theory section of the page. I'm trying my best to explain this so that someone with about the level of understanding of "light has a frequency" will at least sort of grasp the idea. Someone else mentioned that my understanding of RGB additive synthesis versus subtractive synthesis of colors is wrong, so I'll be rereading the chapter from Feynman's book on

      • if you give me permission, would like to adapt parts of your explanation to improve the theory section of the page.

        Go ahead -- I hope, it will be useful.

        Why does red + blue look similar to purple? After a lot of training, I can distinguish between the two (now, magenta really looks like red+blue to me). However, it seems bizarre that a CCD can capture the color purple at all. It's certainly not actually emitting purple light, so it must somehow be converting the purple frequencies of light coming from, say, a flower, into magenta. How on earth would this happen? I can grant that a purple light would excite the blue pixels in a CCD, but it's hard to swallow that they'd magically also excite the red pixels in the appropriate proportion. I feel like if I got an explanation of this, everything else would fall into place.

        Violet (spectral) is perceived to be similar to purple (red + blue) because "green" receptors sensitivity drops faster than "red" receptors sensitivity in the blue-violet range. "Blue" receptors have maximum sensitivity closer to a violet (420nm), and their sensitivity is overall lower than other receptors. So absence of green with red and blue present produces various shades of blue or violet. Blue LED light that we correctly perceive as spectral blue is seen by both

    • Re: (Score:2)

      by AlpineR ( 32307 )
      His explanation is fine. The key point is that light is really a spectrum which means it has an intensity at each of countless frequencies. The human eye has three (or four) sensors that respond to some subset of those frequencies. The result is that the thousands of scalar values describing a spectrum are boiled down to three scalar values by the eye.

      As a consequence, the stimulation of the eye resulting from any spectrum can be mimicked by any other spectrum that stimulates those three sensors in the s

  • Their clean web page needs no apology (Score:5, Insightful)

    by Morgaine ( 4316 ) on Monday March 17, 2008 @03:13AM (#22770994)
    From TFA: Apologies in advance for this being a simple html website. I'm a scientist/engineer, not a graphic designer.

    No apologies needed. I wish all web pages were as clean as yours, instead of covered in irrelevant decor, side panels and advertising that just obscures the message and makes loading times 10 times as long as they should be.

    Google's minimalist search page stands almost alone in retaining functional sanity among major websites. Don't feel bad emulating that frugality.

  • "gets artistic with...art"

    Incredible. Next thing you know, people will be getting ingenious with ingenuity.

  • Luxeon Rebels and Vs? Yawn! I've been running those under PWM for over 2 years. Presently I'm rigging an RGB LEDEngin [ledengin.com] 15W Light Engine w/ 1.5 A buck boosts running through a fiber bundle conduit to drive a DLP. Had to go out and get some arctic silver epoxy and P3 heatsinks to handle the heat.
    Maybe the current state of LED tech will make it to MIT in a couple of years.

    • Re: (Score:2)

      by karnal ( 22275 )
      That's actually something I'd like to see - I'm assuming by DLP you mean projector?
  • I wish I had mod points today for 'informative', because the article points out something that's not intuitively obvious and explains an observation I've made for the past 2-3 years (the time since RGB LED theater lights started to become commonplace) -- why things illuminated by the "white" light from a RGB triad tend to look like crap. Specifically, the observation that if you shine "yellow" light produced by red and green LEDs onto a surface that's painted/colored yellow, the surface looks almost black,
  • However artistic you want to get with LED lights, just don't hang them around town with black electrical tape ;)
  • Color Kinetics (now owned by Philips) has a patent entitled "Multicolored LED lighting method and apparatus" (6,016,038). It's such a trivial invention which should have prior art. Yet they used it against Super Vision International and it was upheld in court.

    I hope this student got a license.

  • Could this ultra-violet LEDs be used to kill the mold and bacteria in the bathroom and kitchen, while nobody is there?

    Or are the rays too weak?

    • The energy density is probably too low, but there are a variety of devices which use UV LEDs to sterilize bacteria and parasites in water. These UV LEDs were designed for use in curing polymers, but the total light output of two LEDs is still only about the same as a smallish blacklight fluorescent bulb. The neat part is that you can get fading UV light (so your fluorescence fades in and out), but the total power output still isn't even close to that of a fluorescent bulb.

      • Re: (Score:2)

        by mi ( 197448 )

        [...] but the total power output still isn't even close to that of a fluorescent bulb.

        Where would one get one of those, BTW? I heard, stores are loath to carry them, because a careless user can really hurt themselves by prolonged exposure.. I'd like to be able to keep it turned on in the bathroom during the day, when we are at work...

        Thanks!

  • The human eye has detectors for exactly 3 colors: red, green, and blue (barring some genetic mutations). The author claims that RGB will let you get close to any color, when in fact it will produce exactly everything the human eye can see and there is no more color information to be obtained by the human eye, period. He then went on to design an elaborate device with for more than the three primary colors.

    Artistically, it's pretty cool.

    Scientifically, I they could have done this with 3 LEDs tuned to exact

    • Sorry, this is simply not true. The eye can see any color inside the boundaries of the CIE chromaticity diagram (http://hyperphysics.phy-astr.gsu.edu/hbase/vision/cie.html). RGB colorspace is a subset of human vision. Colors which you patently cannot produce with RGB mixing, but can see in a rainbow, include: that awesome purple that you see at night on a really clear evening, true deep cyans, and true yellows. This can be seen very well on the illustration on the GSU website I linked to.

      The eye is more a

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