Alan Lewis wrote: > It's very difficult to make hard and fast statements about the > efficacy of LEDs at this time. Standardized measurements have only > recently been developed and published
The main problem has been whether or not to use Candela or Lumens. (I prefer either/both depending). The standardization of these measurements has been so for a long time. There have been some issues with how to measure "white" light from leds though. > and the early round robin tests sponsored by DOE have shown that few > meet the claims made by the manufacturers and distributors. As far as I know most of the failures were due to lifetime and reliability issues. The best known mfgs have always lived up to their intensity/luminosity claims at least when new, and the LEDs now made by them do look to live up to lifetime claims as well. BUT as I have always said there are LEDs then there are LEDs, meaning stay away from cheap Asian LEDs if you really want efficiency and reliability. > Testing and comparisons are on-going. Although there are exceptions, > most white light LED packages still trail the better CFLs in actual > lumens/watt delivered under standardized testing conditions > (monochromatic LED's can be very efficient at some wavelengths, but > lose efficacy when packaged to produce "white" light). Almost ALL white light LEDs/arrays use phosphor conversion NOT color mixing to produce white light! And the CIE index for these is very high that is to say you can get a color temp. now that almost is as good as natural sunlight in their effect for illumination/human perception. And the claim of almost 80 lm/W is NO exaggeration...these things are blindingly bright for just one watt of power. > > LED technology is evolving rapidly and the holy grail of 100 > lumens/watt is still the goal and is considered possible in production > numbers in the not-too-distant future. Problems of lower light output > due to heat remains a real issue. This is indeed the issue. However, a light made with two Rebel leds operating at full power needs a PCB heat sink of about the size of a nickle coin, whereas a led light that made that much output of five years ago needed a PCB heat sink of about four square inches. Huge advance. It is indeed true that now LEDs are significantly more efficient than CFLs one reason the military is switching all CFLs in most applications to LEDs. -Ken _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
