Posted By markever on 04/22/2009 1:34 PM
Dana1
The amount of light that is absorbed by the gel depends on the opacity of the gel. If I use a STRONG RED gel then that will make my light RED, which is not what I want.
If I use a gel that is just slightly red or yellow, then I am actually not using more energy at all, so it is not any less green.
The result is just that I will have SLIGHTLY less light, which is fine with me, since the LED is much brighter than I need it to be.
Either way, I am using less energy than a regular bulb.
It's less about the overall opacity of the gel than it is about the gel's opacity to the color that you're screening out. If half or more of the luminous energy is blue (likely, given your description), then a gel that's capable of "warming" the appearance of the light to a lower color temperature has to be opaque to most of the blue.
If you started out with say 40 lumens/watt efficiency (on the high end for cheapy LED-bulb efficiencies) 20 lumens of blue, 20 lumens of "warmer" color, and you block 75% of the blue to warm it up, you're down to 5 lumens of blue, 20 lumens of other colors, for 25lumens/watt total LED+gel efficiency, which is about where higher-efficiency halogens live (with FAR better color rendering!)
You can always use less energy by turning them off or dimming them, or going with a tiny low-wattage nite-lite but if it's a credible-usable light level that your after, even bottom-of-the barrel low-wattage compact fluorescents are over 50lumens/watt efficiency these days (about where the highest-efficiency not-so-cheap LED replacement bulbs are.) If it's reasonably high AMBIENT light level you're looking for, electronic-ballasted straight-tube fluorescents run 80-120lumens/watt (50-80lm/w with fixture-losses, if the fixtures use diffusers, but much higher in low-loss fixtures using specular aluminum.).
If it's just a tiny to moderate amount of light you need, you get better color rendering & efficiency and literally twice the light out of 2-5W cold-cathode CFLs than bottom-of-the barrel but more expensive LEDs. I must have a dozen sockets in my house stuffed with cold-cathode bulbs in that power range in my house- they're nice! If I found LEDs that filled those functions with higher efficiency & better color rendering I'd buy 'em, but they don't exist... yet. For higher ambient and task lighting I let linear-fluorescents do the heavy lifting.
Don't confuse glare with brightness either. Glare is a function of the contrast in light intensity relative to the field around it. LEDs are by-nature quite glarey since all of the light is being emitted from a very small area- clear-bulb incandescents and halogens have similar issues, which is why lampshades & diffusers were invented (at a net loss in overall efficiency.) True lighting efficiency will likely come when they work the longevity kinks out of organic LED (OLED) technologies, and you can generate high ambient light levels from glowing sheets rather than high-intensity points of light. With lower glare the light becomes more useful and you can even achive the same seeing function at lower lux levles, since your pupils will open up a bit when the glare is gone.
Total lumen output per watt of input is the only first-order credible metric for lighting efficiency. But poor color-rendering can reduce efficacy- you can't see as well, even at high lumen-output with a color rendering index under 50, so CRI counts too. Cheap LEDs lose there too (many are unrated but more expensive ones can be pretty good- some even hit the 90 range.) This is the typical range of luminous-efficiency that's commercially available on retrofit LEDs:
http://www.energyfederation.org/consumer/default.php/cPath/25_3652
I can't imagine doing much more than low-level accent lighting with the 44lumen R20 spot (no CRI rating) like this:
http://www.energyfederation.org/consumer/default.php/cPath/25_3652_2385
But I can read printed matter somewhat comfortably under a 3W 120lumen 82CRI cold cathode R20 flood (5W/200lumens is noticably better). And 2 watt 90lumen cold-cathode A-bulbs are more than enough light for nighttime stairway and alcove lighting (even under lampshades), and aren't source- restricted to a 10-40 degree beam the way most LEDs are.
At 1/10th the price I'd be all over the Cree LR6 for recessed R30 cans in hard-to-reach hard-to-reach places:
http://www.energyfederation.org/consumer/default.php/cPath/25_3652_2382
The LR6 is closest thing I've seen yet to a true ambient lighting source based on discrete LED technology. They're not super-high efficiency, but they're not bad. Self-ballasted CFL-equivalents run in the 60-65lm/watt range instead of 54lm/w, but they'll burn out in 5-15 years and I'm a lazy sucker... :-) -as long as it's not abused by heat or line voltage noise the LR6 would likely outlive ME. (They're under $90 at some web-discounters- I'm keeping my eye on 'em.)
For now the tiny replacement-bulb type LEDs are best used for tiny spot or accent lighting- they're pretty sucky and lower at most other lighting tasks than competing fluorescent, CFL, and HID technologies. But if your alternative is to use an incandescent A-bulb, use LEDs & gels, candles, whatever it takes- almost ANYTHING is more efficient than generic incandescents! There may be a small-but-burgeoning present for LED lighting, but it's long-anticipated future could be huge someday... By the time my CFLs and cold-cathodes all burn out LED technology may have finally, TRUELY come of age. If they ever hit over 100lm/w true-efficiency (measured in line voltage assemblies rather than bare-die-on-test-bench "wow" press release type numbers) I'd buy-in even at $0.15/lumen pricing and retire my fluorescents.
Until then I'll continue view them for what they are- mostly moderately higher efficiency halogen-spot replacements, which is way behind where the current hype puts 'em.