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LED Lighting - The Eyes Have It July 25, 2008... It's about more than the numbers. While great progress has been made in the specifications that will help designers, architects and consumers to select LED-based solid state lighting solutions, there's still more to this than meets the eye. Or rather, it's about what really does meet the eye, as opposed to what the spec sheet tells you. Anyone who knows me will confirm that I'm a numbers guy, so this concept has been one I wrestle with. I'm reminded of the vintage Star Trek episode, Spectre of the Gun (fear not, I actually had to look up the name), in which Captain Kirk and the key crew members are beamed into a representation of old Tombstone, Arizona for a showdown with Wyatt Earp and Doc Holliday at the OK Corral. They brew up a tranquilizer gas that should work, but doesn't. While the team struggles with another way out, ever-logical Spock points out that reality demanded that the gas will work. Since it did not work, he points out, reality is not the operating rule, and therefore, none of it is real and the Earp's bullets won't matter either. And he was right. (And not to leave anyone hanging, once they believed in unreality the bullets passed right through them, allowing a fair fist fight to ensue, mercy to be shown, and the basic merits of the human race were once again demonstrated to some further-advanced alien culture). The 'dose of unreality' that brought this all to mind came yesterday when I had the privilege of a hands-on test of the new Samsung SP-P400B, which is built around Luminus Devices "photonic lattice" or "PhlatLight" LED array. Fear not, lighting folks, this isn't a pocket projector product review, it's a metal halide versus LED slap-down match. After stringing some wires and giving a quick read to the user manual to figure out how to make the picture pretty, we got this all-new, just now available "150 ANSI lumen" juggernaut to display a DVD playing on the laptop. The more observant spec-hounds will notice the still-common ANSI reference and point out that the specifications relating to the measurement of lumens – ANSI/NAPM IT7.228-1997 and ANSI/PIMA IT7.227-1998 – were officially retired on July 25, 2003, due to lack of technical support. CIE lumens are now the real standard, but the lumens come up the same. It's a big hint for everyone that the ANSI spec is still more commonly referred to in at least the projector marketing community - the efforts to maintain one's investment in educating the consumers can outweigh a lot of other factors. The projector itself is only about a 6 x 6 x 3-inch cube, and about 1/4 or less the size of our 2000+ lumen company "presentation projector" that throws enough light to do the job for a conference room of up to 300 or so people (you can see both projectors up close and personal at the upcoming SSLdesign Summit, Aug 26-27 in New Jersey... where, along with our other great speakers, Luminus will share some "out of the box" approaches to general lighting based upon the same technology). With the LED illumination source in there, it has a nice, quiet fan, and more importantly for anyone who has experience the joys of traditional metal-halide projector bulbs, an ill-timed bump while in transit or especially while running, is not going to frag things and leave you with a rather immediate need for a $250 to $350 bulb. The LED solution is also projected to give you a lifetime of 4 to 10 times that of the metal halide. As you would expect the colors are brilliant in comparison to the larger projector's, and here's the reality-challenged part: It seemed every bit as bright despite the 10x disadvantage in its lumen rating. Do my eyes deceive me? Even if it is really only half as bright, making it a 5x disadvantage, there's a spec problem here. One industry-insider that I shared this with commented, "It looks like the industry is starting to realize – and as you have observed in your 'testing', ANSI Lumens don’t predict perceived brightness comparisons between LED and lamp based projectors, and the disparity between LED and lamp ANSI ratings for equivalent perceived brightness is astonishingly large. Just as CRI is an inadequate predictor of perceived color rendering for saturated (RGB) white light sources, white ANSI lumens are not good predictors for LED projector performance. Bulb-based metrics are certainly inadequate for the move to SSL, but change is hard…" [emphasis added]. Color temperature (CCT) specs are another area that highlight the discrepancies, and are the subject of one standards effort underway, in addition other recently completed ones from Dr. Yoshi Ohno's group at the US's National Institute of Standards (NIST). What this means for the general lighting community is that while the continual refinement of the specs will be helpful in any number of ways, it will still come down to understanding where the specs reach their limit and when our eyes have to take over. Jeff Miller, one of our 2008 Summit co-chairs, who is a director with Pivotal Lighting Design, as well as the current president of the International Association of Lighting Designers (IALD), gave a spectacular workshop and talk at our supply-chain oriented Blue 2006 conference in Taiwan. In that talk, Jeff shared the "human factors" that needed to be considered and that are sometimes forgotten by the "semiconductor specification orientation" of the LED community. Things like "acceptable levels of contrast" and the understanding of "a daylighting approach" matter greatly when it comes to the user's lighting experience, comfort and even health. That's part of what the SSLdesign Summit is about, of course, as we've created an agenda that will enable specifiers and luminaire manufacturers to come away with a sharpened knowledge-base to enable them to qualitatively evaluate and implement their designs, whether at the fixture or lighting project level. The networking time will also connect them to key solution enablers to help them get it done (both in the form of people and technology). Change is hard, but it's always worth the effort, and usually successful if you have the knowledge to make it work for you. See the Current Industry News Summary
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