[ QUOTE ]
php_44 said:
If you look at the spectral characteristics of a normal luxeon, it puts out a lot of blue light and some light centered on yellow. It's bumpy and lacking in red light. This light may make some objects color appear differently than it might in sunlight - not great color rendering.
If you look at the spectral characteristics of a warm white Luxeon, it's mor balanced and less bumpy, with an improved amount of red light. This light will render colored objects better than a normal white Luxeon.
[/ QUOTE ]
I need to point out here that the color rendering has more to do with the phosphors used and not the color temperature. I'm guessing Lumileds uses phosphors which get better efficiency at the expense of color rendering on their cool white Luxeons. This doesn't necessarily have to be the case as there are full-spectrum fluorescents which are as efficient as standard ones, get better color rendering, and have a CCT of 5000K to 5500K. High color temperature and good color rendering are not mutually exclusive, at least with fluorescent lighting. Perhaps the fact that a blue rather than UV LED is exciting the phosphor forces Lumileds to use phosphors getting poorer color rendering but better efficiency on their cool white Luxeons. Or perhaps a better phosphor would just be too costly.
Regarding the warm white Luxeons, I personally don't see the point to them. Based on the bin numbers, the efficiency is worse than incandescent, and I don't really see the purpose of trying to imitate a poor form of lighting with an LED just because people are used to it. People get used to smoking, too, and other things that are bad for you. Someone else here said it seems like a step backwards, and I tend to agree. Lumileds should try to match the spectrum of sunlight exactly with their LEDs. Studies show this form of lighting is the healthiest for people. They are just not used to it, and probably have never even seen a room properly illuminated with full-spectrum fluorescents. I equate preference for incandescent type lighting more with a bad habit than anything else. I grew up with mostly incandescent lighting in the 1960s and 1970s and hated it. Blues and greens look washed out, and whites look like an ugly, dingy yellow. Once I was old enough to change the lighting in rooms I used frequently to fluorescent I did so without hesitation, even though cool white tubes of twenty years ago had drawbacks of their own (the worst ones looked greenish). More recently, I discovered that full-spectrum fluorescents look even better than the cool white ones, so much so that I would never go back to the cool whites again except in utility areas. As for incandescents and their imitators, I say we ditch this form of lighting for good and the population will be happier and healthier. I really hope that when the time comes that we see LED screw in replacements for incandescents the situation isn't the same as that which exists with CFLs nowadays-namely that it's next to impossible to find anything other than warm white in most retail stores. I hope there is a least a choice, or better yet that full-spectrum 5000K is the only type sold as nothing else really makes any sense for general lighting (colors for specialty uses would be cool though).
Besides the poor color, I remember another thing I hated about incandescents was the fact that to brightly light a room with them would require like 500 watts or more. I just got tired of squinting trying to find things in rooms dimly lit with 75 W incandescent bulbs, and this added to my general disgust with this form of lighting. Nowadays, I'm seeing chandeliers with those small base bulbs in far too many homes. Those bulbs are even less efficient and more yellow than regular incandescents. Ugh! 300+ watts of power and the room still looks dimly lit. I really think the government should start an anti-incandescent campaign both to save energy and promote better health. I tend to think most people would love full-spectrum lighting and never go back to anything else once they tried it. Incandescents are the SUVs of the lighting world.
