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Comment by Cushman | Hacker News Reader

I wonder what the actual color temperature of the "blue" LEDs is— I've been hoping for a while that the rise of LED lamps would finally mean shifting to more natural colors.

It's kind of absurd to me that in this day and age we're still trying to make our artificial light look like another kind of artificial light rather than sunlight.

(For reference, daytime sunlight is around 5500k— these bulbs are marketed as 2700k, which is about the color of sunset, sunrise, or a large fire.)

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The issue isn't so much the color temperature; it's more about overall color rendering. Black-body radiation, like we get from the sun and incandescents, provides the best color rendering across the whole visible spectrum, assuming a color temp somewhere near the middle.

CFLs aren't too great at rendering, because their phosphors emit very spiky output.

LED phosphors are improving rapidly in this area.

The cool (bluish) white tints of LEDs usually produce the most lumens. As you go to a neutral(5000k) or warm(around 2700k) white tint, the lumens output is lower. I assume they went with a cooler tint to get the most output.

LED production has improved a lot recently and now it's possible to select the exact color temperature of the LED you want to buy. Also, it's now possible to get the same output (800lumens) with only 1-2 LEDs and have a good color temperature without extra steps.

That's because we like the color of fire and always have. The lux from the sun is so high that the color temperature doesn't matter except in photos.

Always have... since the invention of controllable fire by nearly anatomically modern humans? I'm skeptical.

For the entire history of human evolution since the formation of the Earth, that color of light has meant it's almost, or just was, night, and was strictly transient. Just 400,000 years ago it also started meaning that it is night. And just in the last couple of hundred years, with industrialization, it's become the color that most of us see most of the time.

Now, I'm not saying that's necessarily bad— but you gotta wonder why.

My understanding was controllable fire predated anatomically modern humans. I remember one theory that basically said using fire allowed modern humans to evolve with a larger brain because fire aided digestion.

PS: Seems to be up in the air: Claims for the earliest definitive evidence of control of fire by a member of Homo range from 0.2 to 1.7 million years ago (Mya).[4] http://en.wikipedia.org/wiki/Control_of_fire_by_early_humans Note: Homo erectus is fiarly diffrent from Homo sapiens. http://en.wikipedia.org/wiki/Homo_erectus

I heard this theory as well, in a history of science class. The professor claimed that you can extract something like 60% more food energy from an egg by cooking it.

Seems to me that humans who liked the color of fire, and by extension liked fire (or vis versa) did better than those humans who did not like fire (or its color).

I like the color of fire, and I seem to be doing pretty well, if I do say so myself. :)

AFAIK the blue LEDs used in these remote phosphor applications is 550 nm "royal blue" monochromatic chip; you can buy these chips on their own, and they are some of the highest energy output chips available on the market.

> For reference, daytime sunlight is around 5500k— these bulbs are marketed as 2700k, which is about the color of sunset, sunrise, or a large fire.

Cold light will mess up your sleep patterns:

http://en.wikipedia.org/wiki/Circadian_rhythm#Light_and_the_...

(unfortunately I can't find a better source)

So you use a varying color temperature and brightness throughout the day/night cycle.

There's a big difference between cold light a neutral light. Personally I hate "warm" bulbs. I use the "natural" bulbs which to me appear not cool but neutral. I've read that asian nations also tend to use much cooler bulbs and dislike the warm ones, but I can't find the reference now.

Also, according to your Wikipedia article "Lighting levels that affect the circadian rhythm in humans are higher than the levels usually used in artificial lighting in homes".

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