? on ultra-bright LED

Sunglasses of "Blublocker"/"blue blocker" and "ambervision" ilk and the like will remove the blue spectral content, leaving behind an orangish yellow that I consider an unattractive minor improvement over high pressure sodium lighting.

In general, white LEDs tend to easily not do well in home indoor lighting for at least a couple reasons:

1. Higher correlated color temperature past maybe 3500-3800 K or so just generally tends to appear "stark" or "dreary-gray" or both in most home indoor lighting.

4100 K often needs illumination intensity of several hundred to a thousand lux (50-90 footcandles) to "look good". 5000 K does often appear "crisper"/"cleaner" than 4100 K, but can easily appear "stark" or "dreary gray" unless illumination level gets to 1000-2000 lux (90-180 footcandle) range. 6500 K appears to me "usually hopeless" unless illumination level gets to 16-20 kilo-lux (1500-1800 footcandles).

That one can be most-of-the-way-fixed by adding a suitable filter gel to the LED light source - if feasible. I would try 1/2 CTS, 1/2 CTO, 3/4 CTS, 3/4 CTO, and "full CTS" and "full CTO". These are available from some theater supply shops. Major brands are Rosco/Roscolux, Lee and GAM. A common size is 20 by 24 inch sheets. Buy just one sheet of "full CTO" or maybe even nothing at all and chances are good that the shop will let you have for free a sample booklet of filter gels.

1a. Scotopic/photopic ratio: That generally increases with color temperature. (Sorry, I did snip away a reference touching onto this.)

I have noticed it being fashionable to promote lighting having higher s/p ratio. However, I suspect that could be counterproductive in home lighting: Higher s/p ratio makes the pupil constrict - and let in less light. That can make things appear drearier.

Furthermore, it appears to me that some part of sensation of glare tends to get worse with higher s/p ratio and also gets worse when the color is more bluish regardless of s/p ratio.

1c. A few people have trouble when blue spectral content is high, especially if most of the blue spectral content is in a distinct band separated from most of the green spectral content. This problem comes from shorter wavelengths being focused differently in the eye from medium/longer wavelengths. This is more of a problem for people with corrective eyewear. Eyeglass lenses of "tripoly" type tend to be less bad than polycarbonate ones for this.

A Rosco/Roscolux #10 or similar light/bright yellow filter will largely fix that by removing medium and shorter wavelength portion of ther blue part of the spectrum. A milder such filter is Rosco/Roscolux 4530, "30 yellow". However, light processed by such filters ends up not strictly warmer, but also a bit on the greenish side.

1. Another negative effect of higher color temperature light sources in home indoor lighting is red objects being rendered duller/darker. This gets worse when the spectrum has a shortage of red and green content and a surplus of yellow content, for the "correlated color temperature" in question. This "red shortage" occurs with most "old tech" fluorescents (most of which have WW, WWX, W, WX, MWX, CW, CWX, C50, D and DX color codes, with X ones and C50 being less bad), to various extents with sodium, mercury and metal halide lamps, and with most white LEDs.

CTO/CTS filter gels will make the light warmer in color and decrease s/p ratio, but does not do much for fixing "red shortage".

- Don Klipstein ( snipped-for-privacy@misty.com)

Wow. Much info. Thank you, Don. This will probably take a day or two to assimilate, but it is definetly appreciated. I am not sure if you are aware of it or not, but I am not trying to provide for standard house lighting. I built an emergency lantern out of a couple of ultra-bright LEDs, and am trying to make this acceptable to my wife's eyes. I will definetly look into the filter material you describe. My desire to find a pair of Blublockers is a last resort, and hopefully better than the white paper/orange hilighter filters I have in place at this time (which seem to work, but I don't trust them to stay put.) The light doesn't need to be anything approaching "normal" white light, it just needs to be usable in an emergency when the power is out. If I *could* make it appear as normal, white light, that would be fantastic, but this is not a requirement.

Thanks again,

Dave

Wife got in on the game, and suggested parchment paper as a diffuser, in a "lamp-shade" configuration. I cut the bottom out of a plastic bottle, covered it in parchment and taped it in place. Works great. Two LEDs give off light like a 40-watt bult, which doesn't sound like much but in the dark it is incredible. Lamp not sits on the shelf in the study, waiting for the lights to go out. I married a smart woman.

Dave

::::sigh:::

Lamp NOW sits on the shelf in the study...

"... waiting for the lights to go out" Sounds ominous! ;-) Beware, the bottomless bottle bites!

I'm just thinking that hurricane season is right around the corner, and living on the Gulf Coast sometimes gets interesting... :)

Smart. I've used wax paper as a pretty good diffuser (mode mixer), as well. But it's not as good for your purpose, I'd suppose.

Jon

Now I understand you. Right. What you whipped up is certainly "uptown" compared to what my family had during two hurricanes in the 1950's in Lake Charles, Louisiana, i.e one black EverReady flashlight and one olive drab plastic, Army-issue flashlight.

--
Michael

When Ike knocked out our power for two weeks late last year, my wife had to be at work early, early, early, and I was cooking breakfast by flashlight. Should not be a problem if that happen's again (God forbid.) I can even make a second one of these for her to shower by, if she wants. Damn things throw light like a 40 or 50 watt bulb, and ought to last a good long time at only 80 mA load on a dozen AA batteries (through a 7812 three-lead voltage converter.) Time will tell if they do last like I think they might...

Dave

The best kind. Notice: she thinks well sideways, learn this from her.