It is quite interesting that 2700K is often considered to be a "normal" color temperature, even though it is much yellower than sunlight (around 5000K, depending on atmospheric scattering). This stems purely from a technological limitation of incandescent bulbs. The bulb filaments simply cannot withstand a temperature significantly above 2700K. Even though LED bulbs have no such limitations, a color temperature of only 2700K is often chosen.
There is another benefit to <3000K indoor lighting: lighting is usually used in the evening, close to bed time. So a warmer light helps with people's circadian rhythm in preparing for sleep. Remember that light at sunset also becomes warmer.
If all your indoor lighting was 5000K, then it would be like you would be living your indoor life constantly at noon.
It's why software like f.lux was created (and the functionality has been incorporated into some OSes as well).
I believe this is more folklore than science. A significant color shift happens only for a couple of minutes during sunrise and sunset. The change in brightness is probably significant, but it is hard to believe that the color has a significant physiological effect (but the placebo could be very strong!). In my experience, f.lux and co. make it pretty difficult to read text due to the low contrast, and simply changing the screen brightness is much more effective.
> Further analysis of these 15 reports indicated that a two-hour exposure to blue light (460 nm) in the evening suppresses melatonin, the maximum melatonin-suppressing effect being achieved at the shortest wavelengths (424 nm, violet)
> The melatonin concentration recovered rather rapidly, within 15 min from cessation of the exposure, suggesting a short-term or simultaneous impact of light exposure on the melatonin secretion.
> A significant color shift happens only for a couple of minutes during sunrise and sunset.
This seems like a very dubious claim - the "golden hour" is obvious to everyone, and there's an intuitive mechanism for sunlight being "warmer" in the morning and evening (blue gets scattered in proportion to the amount of air it travels through). Do you have a citation for this?
What's true for outdoor lighting is just as true for indoor lighting:
> It is crucial to control upward-directed light, but we now know that the color of light is also very important. Both LED, and metal halide fixtures contain large amounts of blue light in their spectrum. Because blue light brightens the night sky more than any other color of light, it’s important to minimize the amount emitted. Exposure to blue light at night has also been shown to harm human health[1] and endanger wildlife[2]. IDA recommends[3] using lighting that has a color temperature of no more than 3000 Kelvins.
Most people have an expectation that residential lighting is on the "warm" (low color temperature!) side. I have a lot of Hue and Sengled bulbs in the house which are tunable and my son complains that they look "harsh" when they are set to a high color temperature. Myself I do art projects that require making fine sensory distinctions and it clear to me that I can do that better with more blue light.
I've seen high-quality incandescent bulbs however that do very well on my tests despite being "warm" but I think a lot of people like using daylight from out the north window for evaluating prints and it was was a revolution a few decades back when art museums realized that higher color temperature lights brought out colors better.
The TV is a good example because the light from TV is transmitted light, like a stained glass window. The TV can create the widest range of perceptual experience if it has R, G and B colors that are precise spectral lines.
If I'm looking at color prints in a book or on the wall that is reflective light and it is dependent on the spectrum of the room. My main TV room has RGB Hue lights that can simulate "warm" or "cold" light but also specific colors. I think 100% green is the ideal light for hot summer days because a full spectrum is also coming in the windows and it gives the most light for the minimum amount of heat. I also find other colors fun sometimes. The guest room that also has a TV has sengled lights that can be tuned from cool to warm.
RGB lights that can produce saturated colors are not going to render reflective colors so well, see
Personally I like high color temperature light but with the system we have we can have it any way we like. If I really need accurate color rendition I bring in high-performing spot incandescent and maybe someday LEDs. My work is all "born digital" so I spend at least 80% of my time looking at screens and looking at prints, handling paper and such is a small but essential fraction of that.
What I really gotta do though is set my system up so it can vary the room color together with what's on TV, that ought to be cool.
For this reason I think it's great to connect different temperature bulbs to each light switch in your house and switch between them during the day. I keep all of my bulbs on during the daytime and then switch to just the warm ones at night.
> For this reason I think it's great to connect different temperature bulbs to each light switch in your house and switch between them during the day. I keep all of my bulbs on during the daytime and then switch to just the warm ones at night.
If you care that much about that, it would probably make more sense to get something like Philips Hue bulbs that can vary their color temperature.
I have hue builds in my house and have them programmed to warm their color temperature as the day progresses into the evening, and dim themselves down significantly as it gets later.
I'd imagine that the "warm" color temperature is modeled after candle and gas lighting but after reading some articles on the history of light bulbs it seems that all the folks working on it were trying to make the brightest, whitest light they possibly could. Today's "daylight" bulbs would probably be perceived as an engineering wonder by those folks.
Humans have used fire probably for their entire evolutionary history. Before language and but after stone tools. The desire for a light spectrum at night similar to what a fire gives off surely comes mostly from that long genetic history.
Nowadays the situation is better, but for years after incandescents were banned in California, the only LED bulbs available in stores had a huge spike in the blue part of the spectrum, which I experienced as painful and now know probably caused the death of some of the cones in my retina through oxidative stress.
(I am over 60 and have some health problems that chronically elevate my levels of oxidative stress -- in all cell types, though the light-detecting cells in the retina are more vulnerable than other types of cells are.)
I.e., I wanted to buy an LED that vaguely approximated a 2700K incandescent, tried many brands, but could not find one, so I don't know what you are on about.
Bright blue light will make a brain more alert -- and the effect is immediate. That is probably why you young people like it, but I am baffled by your "a color temperature of only 2700K is often chosen" (not that color temperature is a useful way of summarizing the spectrum of and LED bulb).
Not just incandescent filament bulbs, the original artificial light was literally incandescent - gas lamps, oil lamps, beef tallow, candles, tallow etc.
> Even though LED bulbs have no such limitations, a color temperature of only 2700K is often chosen.
I think there's a reason for this, which is that sunlight supplements indoor lighting during the day. People rely on indoor lighting more at night when those warmer tones are most desirable.
