Daylight vs 5000-6500K LEDs

[Orion]

This might have been discussed before,....but I was curious about something. Daylight has a Kelvin of 5000-6500. When I look outside, during the day,...it looks "warm" in color. But a flashlight with an LED that is 5000-6500 Kelvin looks more blue-ish and doesn't have that CRI color tone people like so much.

So.......you know...........what up with that?

 

[alpg88]

Spectrum. Daylight has full spectrum of visible light, artificial lights, especially leds have a very narrow band

 

[aznsx]

This might have been discussed before,....but I was curious about something. Daylight has a Kelvin of 5000-6500. When I look outside, during the day,...it looks "warm" in color. But a flashlight with an LED that is 5000-6500 Kelvin looks more blue-ish and doesn't have that CRI color tone people like so much.

So.......you know...........what up with that?

I am no expert on this subject, but have found neither are some who think they are! Remember this stuff is somewhat subjective as well, so it can be tricky. You'll get as many opinions on this as there are stars in the sky!

I get what you're saying. I've found that I prefer a CT a bit warmer than I originally thought I would; usually between 4000 and 5000. 4500 seems a nice compromise to my eyes, although some look OK up to ~5500, depending on the LED. I get the blue cast you mention above that. In my experience, the 'ideal' can vary with the specific application I'm using them for (the environment and what I'm illuminating with them). Many LEDs (including some 'high CRI' examples) are also rather weak in R9 CRI, which doesn't help with the spectral balance, and that can factor into this.

Photos can be misleading, but this is the 'cheat sheet' photo I often use to reference, and have found it useful in determining the approximate CT of LEDs w/ my eyeballs:

https://nebula.wsimg.com/c0a7561d1a6a5daab692829db941ed14?AccessKeyId=C99B867E55D391A76D29&disposition=0&alloworigin=1

That photo is from this source, so full credit to the provider:

Color Temperature, Color Accuracy and Color Rendering Index

www.americangreenlights.com

 

[idleprocess]

It's all about context.

• Middle of the day daylight at >5000K is overwhelming to the tune of some 1000 watts per square meter. It snaps those pupils nearly shut and is everywhere, forcing your visual perception to adapt. But this is what our eyes are adapted for so it looks right.
• Step indoors into a well-lit space 5-10 meters away from any windows and suddenly 5000K overhead lights would look cold by compare since there's a good 2 orders of magnitude less light energy involved. In fact 5000K will look sufficiently cold that it's not the color temperature of choice in workplaces and retail - CCTs around 4000K are preferred in general lighting for a neutral cast (at least in workplaces where promoting alertness is important).
• Step into a home lit more comfortably than a public space more relaxing than a workplace - likely an order of magnitude less light energy per unit area - and the preferred CCTs will tend to drop again because the home is about relaxation and leisure.
• Step into the dark and even relatively low CCTs like 3500K can appear to be an almost stark white because you're experiencing something close to the maximum possible contrast - a pool of bright light dropping off to darkness with your color vision and night vision in mild conflict.

At each step your pupils dilate to collect more light and your eyes have to work with ranges off by both orders of magnitude and wildly varying min/max values for each situation. Something that's perceived to be dark in daylight could still be beyond the top of the scale in an office setting.

On a related note, outside of bright sunlight-like conditions, cooler CCTs are subjectively perceived to be brighter than lower CCTs even when the lumens are the same.

 

[Orion]

Thanks for the comments. I recently purchased a flashlight [in the mail, currently] that is the cool white,....and only got it because it was the only color temp for the flashlight body color that I wanted. So I compromised with the 5000+ Kelvin temp.......even though I prefer that ~ 4000. Oh well. The body color was important enough.

But thanks for the look at color temps and how our eyes react towards them. Quite interesting!

 

[LEDphile]

It's all about context.

• Middle of the day daylight at >5000K is overwhelming to the tune of some 1000 watts per square meter. It snaps those pupils nearly shut and is everywhere, forcing your visual perception to adapt. But this is what our eyes are adapted for so it looks right.
• Step indoors into a well-lit space 5-10 meters away from any windows and suddenly 5000K overhead lights would look cold by compare since there's a good 2 orders of magnitude less light energy involved. In fact 5000K will look sufficiently cold that it's not the color temperature of choice in workplaces and retail - CCTs around 4000K are preferred in general lighting for a neutral cast (at least in workplaces where promoting alertness is important).
• Step into a home lit more comfortably than a public space more relaxing than a workplace - likely an order of magnitude less light energy per unit area - and the preferred CCTs will tend to drop again because the home is about relaxation and leisure.
• Step into the dark and even relatively low CCTs like 3500K can appear to be an almost stark white because you're experiencing something close to the maximum possible contrast - a pool of bright light dropping off to darkness with your color vision and night vision in mild conflict.

At each step your pupils dilate to collect more light and your eyes have to work with ranges off by both orders of magnitude and wildly varying min/max values for each situation. Something that's perceived to be dark in daylight could still be beyond the top of the scale in an office setting.

On a related note, outside of bright sunlight-like conditions, cooler CCTs are subjectively perceived to be brighter than lower CCTs even when the lumens are the same.

Yep. This has been known about since the 1940s: https://en.wikipedia.org/wiki/Kruithof_curve
Note also that there are regional/cultural preferences for CCT as well - some parts of Asia prefer very high CCT illumination, while US consumers tend to prefer low CCT illumination.

 

[idleprocess]

Note also that there are regional/cultural preferences for CCT as well - some parts of Asia prefer very high CCT illumination, while US consumers tend to prefer low CCT illumination.

For sure. And the regional/cultural preferences are generalities at that. i.e. I don't much care for sub-3500K myself.

 

[aznsx]

Yep. This has been known about since the 1940s

Yep, human vision (and hearing) involve fairly non-linear devices. It's a bit like the visual equivalent of the Fletcher-Munson curve, etc., etc. Very non-linear animals we are in many ways, even before subjectivity is considered. Add all that to ambient / environmental factors, and it's no wonder no one seems to agree on much!

 

[jon_slider]

how blue 5000K looks, depends on the time of day

when our brain is white balance adapted to daylight, a 5000K LED does not look blue-ish

otoh, when our brain is white balanced to 3000K or warmer light, such as incandescent or fire or full darkness, then a 5000K flashlight will look relatively more blue, than the ambient light that the brain is adapted to, at the time.

so, a 5000K is a great option for daytime use.. it can be fine at night too, if the use case calls for staying alert and focusing attentively on details.

otoh, a 3000K light is more relaxing. Less blue light helps our body to produce sleep hormones that help us calm down before going to sleep.

then again, a 3000K light will look very warm during the day..

courses for horses

 

[Orion]

For home, I definitely want closer to that 3000K figure. I've seen apartments with extremely cool LED lighting and I would find that very unpleasant.

But for a flashlight, I am thinking that it is okay to have that 5000-6500K if you're wanting to use it for really seeing things in detail. I'll know better Saturday night when I pull it out of my mailbox and charge up the battery.

It's an Olight Seeker 4 Pro, btw.

 

[18650]

This might have been discussed before,....but I was curious about something. Daylight has a Kelvin of 5000-6500. When I look outside, during the day,...it looks "warm" in color. But a flashlight with an LED that is 5000-6500 Kelvin looks more blue-ish and doesn't have that CRI color tone people like so much.

So.......you know...........what up with that?

Are you looking outside at sunrise or sundown? During the midday I don't see this warmth you're talking about. The cool effect is even more pronounced on cloudy days. Bear in mind that warmth can also be greatly affected by what objects are in the surrounding environment reflecting the light into your eyes.

If you haven't yet already you should check out something with the Nichia 519A in it. The 5700K R9080 version looks great.

 

[jon_slider]

fwiw, common use of the term Neutral Tint, is a misuse of the term Tint,

when they actually mean Neutral White Color Temperature


BBL = Black Body Line, aka Neutral Tint line
CCT = Correlated Color Temperature, for example 4500K is a Neutral White Color Temperature. It is not correct to call 4500K a Neutral Tint.

 

[Orion]

So I got the Seeker 4 Pro, last night.....and I like the beam color. It doesn't have any hit of a "blue-ish" tint at all. Shining it against my white door, along with the Seeker 3 Pro, the 4 Pro is a tad more white. But I'm good with that. I have lights that are warm. One that I...kinda think...is too warm. It lives on my nightstand now...because that color tone is better for eyes that have been in the dark awhile.

I'm glad I got this 4 Pro. Love the Midnight Blue color! The switch is similar to the 3 Pro, but works quicker, and starts at the lowest output. For the 3 Pro to get to the lowest, you have to hold the switch. So I like the interface of the 4 Pro better.

 

[kerneldrop]

SFT40 is another low-CRI white that is really white and nice looking.