There are RGB lights with color control. I expect that will eventually become common, partly because, in principle, it is more efficient to make three colors directly than to use phosphors. The ones we have are 12 volt and have remote control. They are not perfect but do work.
In the future, I expect three or four layers for colors, like photovoltaic cells I read are under development.
I also thank you for the research.
> WK40
Amazon $50; changing the emitter and a NiMH-voltage driver on top of that. Not likely affordable.
Found mention of these at: What options are there for 3xAA (or 4xAA) flashlights?
Aurora SH-3AA for $26.31
UltraFire SH-3AA for $26.34
This would be good —- it’s out of stock — 3xAA for $12
but maybe I can find it elsewhere.
That’s more in the ballpark I’m looking for.
> RGB
If you don’t turn on the blue, mixing red and green would produce the subjective experience of seeing yellow light — that’s our color vision receptors and brain color sense working.
But green LEDs generally emit down into the 450-nm range, like this:
and inexpensive RGB aren’t going to offer a whole lot of choice about what green emitter is used.
The receptor in the retina for melanopsin is sensitive in the 400-500 range — it isn’t a color receptor. It’s like them but different.
It’s a different chemical attached to a different set of nerves in the retina, the ones just recently discovered.
It can’t be ‘fooled’ into seeing yellow by mixing red and green. It reacts to the photons below 500nm no matter where they originate.
1. Why change the driver? It's not a Li-Ion light.
2. Can often be had a bit under $20 in Xtar's ebay auctions.
If they're still around, the Defiant 2xAA lights were $7.99 for a 2-pk., IIRC. Cheap.
For 2x18650, there's the Ultrafire 502D, ~$12 as complete light, I don't know about host.
For the price of those SH-3AAs you could get a much better XinTD X3.
That Tractor Supply light shows as in stock for me, both online and in stores nearest Berkeley.
Another different approach is to add your own remote phosphor. I have had some success with that, though I didn’t have a way of applying the phosphor evenly. I read that remote phosphors are more efficient than contact phosphor, because they don’t scatter light back into the junction. But for this discussion, they are much easier to add. Phosphor is also called day glow and is fairly common in a variety of colors and forms. I painted the outside of a cool white LED bulb with a thin coat of yellow day glow model airplane dope and then with a thin coat of orange-red day glow craft type paint. I got a very warm white. The unevenness didn’t matter much because it was not visible directly. Another approach would be to sew a day glow T shirt inside a lamp shade.
I put the yellow first and then the red, because light can only be converted to a longer wave length. Light hitting the red first and then the yellow might be lost, while some yellow light is converted to red. Such phosphors may not be as good as the ones LED manufacturers use, but I think they are at least a lot better than using filters.
The luminance is much reduced, so one can’t make a throwy flashlight that way, without double focus optics.
> under $20 in Xtar’s ebay auctions
Now yer talkin’ — didn’t know that.
Not ideal for these folks as it starts on turbo — starting low is always preferred for dark country/low light locations.
But I did bid on one WK40
but I think they saw me coming.
I’ll haunt ebay for a while and hope to catch lower prices eventually.
> add remote phosphor
I bought some and some royal blue emitters — Digikey, I think it was.
But I checked — this is the $40 kit spectrometer I have — http://publiclab.org/wiki/spectrometer
and some of the blue leaks through
The WK40 is dual-switch, on/off/momentary at tail and change modes via side switch. Always comes on whatever mode it was shut off, unless it was shut off in a blinky mode, then it starts on low.
too bad the BTU magic scorpion transformer is so expensive.
In one of your responses you said “It can’t be ‘fooled’ into seeing yellow by mixing red and green. It reacts to the photons below 500nm no matter where they originate.”
We know that the mfg’s use yellow over the blue to make white. So my question is will any “blue” led fool these “sherlock holmes” cells?
(because it seems they cant be fooled)
I have recently installed some amber led strips in my bathroom & bedroom to optimize melatonin production.
I turn them on the last hour or so when i get ready for bed, i have had extreme insomnia all my life so i am always looking to improve the efficiency of my sleep.
Nowadays it isn’t so bad, i formulate my own liposomal melatonin solution, and use 2-3mg melatonin every night, and sleep much better.
F.lux is also a good tips to install on the computer & phone.
As far as i know you can’t use remote phosphor amber led’s to improve melatonin production, some of that blue light always gets through.
You don’t want that “nicer” more fully spectrum color light of remote phosphor led but only pure amber or red.
Even green spectrum light can have a detrimental effect on melatonin production, not as bad as blue though.
The body is so sensitive to blue that in one test they shined a blue led at the back of the knee on subjects, and completely shut down melatonin production 
thats just crazy. EDIT it seems it doesn’t 
interesting.
That candle light-style oled looks great where can we buy some of that?
Wow I did not know such a thing existed. will try tonight. thanks
> back of the knees
Nope.
That failed to be replicated, though it took a while and you’ll still see the original claim repeated.
As the White Queen said to Alice, “It’s a poor sort of memory that only works backward.”
Nowadays, when I remember something, if I’m being smart, I ’oogle it and find out what’s new since I came to believe it …
http://www.google.com/search?q=light+“back+of+the+knees”+sleep
http://www.genomenewsnetwork.org/articles/08_02/bright_knees.shtml
> f.lux
So far those who’ve checked finds f.lux lets significant blue through. It changes the color balance but doesn’t block the blue band.
The one published science study I found didn’t actually check, they just assumed f.lux worked. They were surprised by their results.
Craig at LEDMuseum is — I’d say — the world’s greatest resource on LEDs generally and has been since the old Usenet days.
Here (page down a bit) he shows
the spectra from his Asus monitor displaying white (without f.lux) (above)
and then to compare:
using f.lux
That’s from:
Always remember — YMMV, it’s very young and older people more likely to notice this than young to middle-aged adults who have better sleep overall.
Interesting that the light behind the knee was disproven, good to know
But that f.lux on LEDMuseum i am not so sure of, f.lux have a lot of different settings, that test must be of an very old version.
Try it yourself set it to ember 1200K or candle 1900K or even darkroom mode.
I don’t use it that warm it gets to hard to read text fast for me then, but i use Dim Incandescent 2300K, Incandescent 2700K or Halogen 3400K, it strain my eyes much less.
Anyway i like it, even if some blue gets through it is much better than nothing and just stare at an calibrated 6500K monitor before bedtime.
You say “They were surprised by their results.” what where the results?
Most anything is better than nothing, I guess.
But the comparison I make is to no-blue-light, because you can accomplish that if it’s what you want.
That’s how people lived, up through the gaslight era — gaslight is a bit bluer than candlelight but it’s basically greenish yellow.
We didn’t have blue light at night to any important degree until arc lights and thorium mantles on gasoline lanterns, and then electrification — just a few decades ago.
It’s a great experiment. The epidemiologists are having fun with it.
Rosco’s one supplier (good photography shops and theatrical suppliers will have, or be able to order, any of their gel filters.
Each of their colors is shown with the spectrum it transmits. Orange and medium amber are best in my experience.
Look for Roscolux #23 orange 
hank, make sure you check back at my post, it looks like we both likes to ninja edit 
Yep, doing that. But I’m about done — this stuff is all documented better elsewhere, and like I said, I have to look up everything I think I know every time I get into posting about the subject.
Always something new out there.
Science. It works.
Yeah it is about 00.47 here in Sweden, and i will not be sleeping for many hours yet.
Thats one of the problem(or maybe advantage ;)) with using melatonin as a sleep aid for me, because it basically resets my production every time i use it, i can twist and turn my sleep pattern with very little health impact, as long as i get enough hours of sleep per every 24 hour cycle.
But i have always been a weird/bad sleeper, i usually starts to wake up and get really clear minded after 22.00.
Yeah that #23 looks interesting but, still some blue gets though & the efficiency looks bad at 32%.
But if i can buy it for reasonable money here in Europe i would still like to test what it would do to some incandescent lights.
I know there’s a line by a company called GAM, and probably others out there.
Your local theatre company’s lighting supplier, or a photography store, should be able to give you the equivalent if the Rosco brand is not locally available.
Roscolux #19 “Fire” and #22 “Deep Amber” are on my list to try the next time I buy sheets of this sort of thing.
I started off with their #10 yellow, but over several years have realized I like the darker shades better — and even with the darker filter gels I’ve tried so far, at night without other lights around, the lowest brightness of both my computer monitor and my old Palm PDA are plenty bright for reading text.
But — see why I’m looking to make my friends flashlights with
simple amber light sources? They can be plenty bright, without noticeably bothering even a new baby’s or older adult’s sleep.
Ok, so are you already using gel filters on your computer, then please test some of the lower kelvin settings on f.lux & compare, it would be very interesting.
Unfortunately i don’t think i can use gel filter on my monitor because it is a 46 inch hdtv, but maybe i am wrong & they make that big filters but it would still be a hassle to change every day at sundown
But for my phone i definitely want to try it out
That sharp amber point on the spectrum is why i like this in room amber lights, it is still bright but only amber, i have ordered some red strips also to combine the amber with to get a little wider spectrum.
I don’t have the high end spectrograph, that’s Craig at LEDMuseum who posts those.
The gadget I have is a $40 kit that’s much simpler. But I’ll poke at it as time allows.
Short answer, though, is that I’m not interested in “white” LEDs or fluorescents (remembering that a white LED is a phosphor over a blue emitter) until someone claims to have one that actually does omit the blue band. So far I’ve seen lots of stories about how they’re working on that but nobody has claimed to have it yet.
I have asked the f.lux people for the information about actual measurements from their product — maybe if you ask them you’ll get a response. I never heard anything.