# What colour temperature is subjectively closest to "pure white"?



## Twinbee (Aug 15, 2010)

My question falls more into the realms of subjectivity, but it should be possible to get a consensus on what most people would consider the most 'white'.

Standard incandescents have been around for ages, and I'm sure 99% of people wouldn't consider them nearly close.

A few years ago, I thought 6400k would be the closest to pure white. But I'm beginning to wonder if this hue is slightly veering towards blue after all. I remember reading a not-strictly-scientifically-controlled study done by someone who showed a range of hues to students and they said that temperatures around 4000-5000k were closest to what they perceived as true white.

I also came across this page, which also suggests 5000k is true white. Other sources will vary from anything between 4000 and maybe 7000 for their definition.

I bet you guys may know better though. Sources appreciated too.


----------



## StarHalo (Aug 15, 2010)

*Re: What colour temperature is subjectively "pure white"?*

There is no pure white; you're always going to bias one light source against another, so if you're been in 4300K lighting and move to 6500K, it'll look cold, if you've been in 8000K lighting and move to 6500K, it'll look warm, etc.

The manufacturer that for me personally has always gotten closest to an all-around usually-looks-white is Jetbeam, but they don't list what the color temp of their emitters is (it's probably somewhere around 5000K), but again, it'll look warm or cool depending on what you've been viewing before..


----------



## ElectronGuru (Aug 15, 2010)

*Re: What colour temperature is subjectively "pure white"?*

My testing shows 4300K to be the mark, but 4200-4600 is close enough in most applications. 5000K is still pretty blue. 3000K is quite yellow. 

One of the issues is that this scale is designed from the use of a single technology (glowing hot metal). So a non-glowing-metal source (LEDs for example) can be (measure at exactly) 4300K and still be tinted with a color not on the color temp scale, like green.


----------



## Twinbee (Aug 15, 2010)

> There is no pure white; you're always going to bias one light source against another, so if yoau're been in 4300K lighting and move to 6500K, it'll look cold



Yes, but that's just the sensory contrast of going from one situation to another. If you stick in one enviroment, then there should be a colour temperature that's closest to what most people would consider pure white (as you imply yourself afterwards).



> My testing shows 4300K to be the mark, but 4200-4600 is close enough in most applications.


Interesting, and it does seem to tally up. I'll read that page more closely soon, but in a nutshell how did you arrive at that figure? Intuitively, it would seem that only testing what people would consider closest to white (and then averaging the results) would be the only way, but I could be mistaken.



> So a non-glowing-metal source (LEDs for example) can be (measure at exactly) 4300K and still be tinted with a color not on the color temp scale, like green.


Yes good point.


----------



## StarHalo (Aug 15, 2010)

Twinbee said:


> Yes, but that's just the sensory contrast of going from one situation to another. If you stick in one enviroment, then there should be a colour temperature that's closest to what most people would consider pure white (as you imply yourself afterwards).



Right, if you're in a 3000K room, a 4500K light will look pure white. The problem is, once you move to a 6500K room, that same light will now look warm.


----------



## Twinbee (Aug 15, 2010)

> The problem is, once you move to a 6500K room, that same light will now look warm.


...until you get accustomed to it. Let's assume you're going to be in the same room for at least say, 5-10 minutes.

Or let's assume that I fill my house with the same colour temperature bulbs. Going from one room to another now won't produce any difference. Question is, for a true white hue, do I go filling my house full of 3500k bulbs, 7000k bulbs, or something in between.


----------



## StarHalo (Aug 15, 2010)

Twinbee said:


> ...until you get accustomed to it. Let's assume you're going to be in the same room for at least say, 5-10 minutes.
> 
> Or let's assume that I fill my house with the same colour temperature bulbs. Going from one room to another now won't produce any difference. Question is, for a true white hue, do I go filling my house full of 3500k bulbs, 7000k bulbs, or something in between.



I should complete the sentence as follows: "Right, if you're in a 3000K room, a 4500K light will look pure white. The problem is, once you move to a 6500K room, that same 4500K light will now look warm." So there is no one color temp you can make a flashlight that will look white even a majority of the time, because the environment you're using it in is always changing.

As for lighting your house, you have to be careful with how cool you get, otherwise it just looks like you're lighting your living room with garage worklights; there needs to be a bit of warmth to house lighting to prevent it from looking too sterile. I find ~3500K works nicely in office and bathroom lighting, and ~3000K is about right for bedrooms and living rooms.


----------



## TedTheLed (Aug 16, 2010)

I'd say since we've been walking the earth for the past 250,000 years or so the light we are most used to seeing things in has been the sun shining in the morning and the afternoon.

the sun is whitest at noon, directly overhead, at 5500K.. a little before and after noon the sun is a bit warmer, or yellower, the way we see it most of the time..

so I'd say light your house at 4800K or so for the most 'normal' / slightly warm appearance of everything.


----------



## X Racer (Aug 19, 2010)

4500k to 5000k


----------



## Twinbee (Aug 19, 2010)

> So there is no one color temp you can make a flashlight that will look white even a majority of the time


.
Oh I see. I was talking though about just room lighting, rather than flashlights. You're right about how 3000k may make the house look warmer. However, I've often thought instead of making the light warmer, have it as neutral, and simply make the furniture colours warmer. That way, other things can be seen with all colours (even blues), whilst the general surrounding will always be 'warm'.



> I'd say since we've been walking the earth for the past 250,000 years or so the light we are most used to seeing things in has been the sun shining in the morning and the afternoon.


I've sometimes thought along similar lines, but I'd be wary, especially as the colour temperature varies throughout the day. So we can't really get an exact figure that way.


----------



## StarHalo (Aug 19, 2010)

Twinbee said:


> I've often thought instead of making the light warmer, have it as neutral, and simply make the furniture colours warmer.



I've used this trick in office lighting before, but it's really more to do with paint than furniture; the trick is to use a warm wall color (anything with a touch of red, which is a broad range of colors), then any accents that are white, replace with an off-white, like a bone or light cream shade. It makes the workspace stand out, but so do skins tones and clothing colors, so I still don't recommend the technique for family/gathering places..


----------



## jtr1962 (Aug 19, 2010)

Humans have a built-in color balance in their brains. As a result, a fairly wide range of color temperatures look "white" once you get used to them. The real question should be what color temperature looks white to us without this automatic color balance? Speaking from experience, this is likely to be the most pleasant color temperature to live under because our brains won't be constantly trying to correct for white.

The answer is it varies from person to person, but it is a given that nobody can auto color balance at the extremes of the scale. Because of this, they are to be avoided. Generally CCTs less than 3500K, or more than about 7000K, fall outside the range. I personally find that I get headaches when under incandescent or similar yellowish light for prolonged periods precisely because my brain is trying ( and failing ) to correct for white balance. Same thing for very bluish LEDs. Probably right around the middle of the scale, 4500K to 5500K, is where things look "white" without your brain doing any correction. And this makes sense from a biological perspective, because this falls within the range which sunlight has during most of the day. Confounding things a bit is the Kruitoff Curve. Lower light levels can skew the midpoint CCT down. Under typical room lighting conditions, ~4000K might look white, while 5000K looks slightly blue.

I personally have standardized on 5000K everywhere. It hardly makes things look clinical to me. Rather, it helps me see as well as possible, and that's really the point of lighting. If creating an "ambience" by using low CCT lighting means vision ends up being compromised, then it's not a good idea. That's why I generally don't understand the use of 2700K or 3000K in the home. The end result looks like you put a sodium vapor streetlight indoors. All lighting should seek to mimic the sun. That's what humans see best under. If you want to have accent lights here or there to give a hint of warmth, that's fine, but they shouldn't be the primary light source. Better yet, just use warm colors if a warm appearance is what you're after. Honestly though, I'm not a big fan of warm tones anywhere, especially after this heat wave.


----------



## StarHalo (Aug 19, 2010)

It makes sense to our man-logic that you should fill a room as amply as possible with scientifically-approved photography-studio-ready light that is ideal for reading and working. But if you think back to those spaces you remember best, such as areas in a museum, restaurant spaces that really stood out, etc, you'll find they pretty much all had warm lighting. I would agree with the above posters that mankind is accustomed to outdoor ambient sky lighting, but I would also submit that wherever man gathered in the evening, there was always warm light; first from the open fire and then from the lantern. The cozy and welcoming soft light offered the safety and camaraderie that our ancestors sought out, and is still instinctively linked in our minds to the above notions like "welcoming" and "soft". 

Not every space needs to be a lit like a laboratory..


----------



## jtr1962 (Aug 20, 2010)

Well, she would look good no matter what light she was under. :thumbsup:

I've heard that warmer lighting flatters skin tones. If you're talking about relatively pale northern Europeans who might look almost pasty white under sunlight, then probably true. If you're talking Asian and/or Mediterranean people, then not at all. Especially Asians since some have a yellowish tone to their skin to start with. When that's the case, yellowish lighting ends up making them looking orange. Mediterraneans with olive skin don't look much better under yellowish light either.

Climate also has something to do with it. Hotter regions tend to like cooler lighting and vice versa. Last thing I need when it's 90 degrees out is to come into a room where the lighting reminds me of being near a fire.


----------



## blasterman (Aug 22, 2010)

Years ago I did a lot of very color intensive video analysis, and after about a year I learned to differentiate down to about 1cc if I was relaxed enough. So critical was our work that any slight deviation in my color correction resulted in the rest of production being off and it being obvious. I needed to keep 'zeroed' at all costs, and I quickly learned what things caused me to drift off. Even going to lunch and spending time in the bright sun for 45minutes screwed me up. Or, wearing colored sunglasses for more than a few minutes. Even ambient room light causes your reference point to move. 

The problem with using artifical lighting as a CCT reference is other than the sun, or maybe Xenon, other common sources like fluorescent tubes or halides or increasingly LEDs do not have flat spectrums. These light sources are typically blue-green generators with just enough yellow and red to qualify for a CRI stamping. 

Given a typical artifical light source, like a LED or fluorescent tube, if you lined 10 different color temps up and put them in a room with any type of ambient I'm pretty sure a random sampling of people would pick light sources around 4100k as being neutral white. If you upped the CRI to 95 I'd would bet that picked sample would start to creep up towards 5000k. 

We often refer to 4100k as being unofficial white, but I think this has less to do with a technical index than the fact that common color spikes in artifical light sources skew what we think is white. Get rid of the spikes and our preference would move up towards the CCT of natural sunlight.


----------



## Twinbee (Aug 22, 2010)

Interesting posts again - I thought this could be the best forum to post under 

I tend to think one can 'get used' to a near-white hue as being more or less white, but that still it would have a subconscious 'off-white' hue to it, without that person really even knowing consciously. Could be wrong though. When a shade is so close to white it's hard to distinguish, then that's half the problem anyway.

jtr1962, I tend to think that 4-5k light is 'best overall' for similar reasons to you. Perhaps some people think 4500k+ light is 'clinical' because of the poor CRI / green (and maybe other) spectrum spikes - is that a possibility? In any case, it's nice to have a variety sometimes (I was even thinking of using 2-4 different colour temperatures in one room to create more interesting lighting - This pic shows what that might look like despite the strange object matter).

blasterman, very interesting again, and pretty close to ElectronGuru's estimate. Curious also the way you say it'll creep up to 5000k with a higher CRI. Would the lack of the spectrum spikes really do that?

I think at the end, I'm a little surprised scientists haven't actually performed this experiment on the public because it's pretty trivial to test for. It would also stand as a reference point to what monitors should use for white. Okay, that almost sounds naive. They surely "must have" done this experiment to set a standard reference white for the world to use (or more likely, some other more accurate metric than colour temperature I guess, but then one can always convert to colour temperature afterwards...).


----------



## Twinbee (Aug 23, 2010)

Just to add this to the confusion. Apparently, most standards use 6500k as a white/grey level, despite the other evidence that hues closer to 4-5000k are seen as more white-ish generally. I wonder what gives...

Here's some quotes from:
http://en.wikipedia.org/wiki/Color_temperature

"The NTSC and PAL TV norms call for a compliant TV screen to display an electrically black and white signal (minimal color saturation) at a color temperature of 6,500 K"

"Digital cameras, web graphics, DVDs, etc. are normally designed for a 6,500 K color temperature. The sRGB standard commonly used for images on the internet stipulates (among other things) a 6,500 K display whitepoint."


----------



## lyyyghtmaster (Aug 23, 2010)

Yes, I've wondered this too about display screen lighting- it seems a screen at 6500K looks warmer than a room at 6500K, even if using the same light source (triphosphor or white LED for example). Could it be because the screen is a large, diffuse source similar to viewing something outdoors against a bluish sky?

I tend to use 6500K indoors in all spaces (living and work) for working, etc but I also have warmer sources in all the living spaces for use when I want to set a mood or it gets late and I want to wind down. Or I could use a CCT-controllable LED fixture to do this, but I haven't actually done so yet.:shakehead

I can't stand 6500K CFLs with a green tint! And most (all?) manufacturers make them that way. TCP used to make a beautiful 6500K product that looked slightly lavender compared to other manuf. products but was closest to sunlight in terms of having no color tint. Then they went to the typical greenish-tint-phosphor fare.:fail: Probably because this has slightly higher lumens due to green looking brighter. And/Or maybe the greenish-tint phosphor blend is cheaper???

I think that the tendency of most artificial sources to need to be warmer than continuous-spectrum sources (which I've noticed myself too!) is due largely to the lack of red, and particularly deep red, that correctly renders skin/wood tones. To try to compensate for this, we use warmer CFLs, LEDs, and metal halides than we otherwise might, in a fruitless attempt to correct for the lack of deeper red so wonderfully prevalent in hotwire sources and sunlight. High-CRI "natural white" LEDs are noticeably better at this, as are true "full-spectrum" fluorescents. Grocers often use high-CRI sources to display meat under.

It's too bad the CRI index is so incomplete, taking only 8 color comparisons for the basis of it's calculations of CRI. And deep red ain't one of them:mecry: Luckily it seems that higher-CRI sources also tend to have more deep red anyway!

Or notice this: even in the early morning, before the sun rises, the skylight does a surprisingly good job of rendering wood tones, even compared to our "neutral" artificial sources! And golly, that skylight has to be 20 000 K or more! Sure the spectral power distribution is skewed heavily towards the blue. But since it's coming from a mostly-continuous-spectrum incandescent source, the deeper red is still present in significant amounts!

I recognize that adding deep red makes the source efficacy lower since the red is harder to see, for the same power level, than that orangey drivel that passes for red in a CFL. But in some cases definitely worth the tradeoff!!!

I've noticed that normal-CRI phosphor-converted white LEDs, of all color temps, tend to render non-fluorescent orange objects as yellower than they are under most other sources. Of course this is also due to the preponderance of yellow over red in the spectrum. This can also be observed on varnished wood.

The Kruithof curve results may be due to the fact that in nature higher-CCT sources tend to be brighter (the sun) than lower ones so our brains "expect" that.


----------



## ElectronGuru (Aug 24, 2010)

lyyyghtmaster said:


> It's too bad the CRI index is so incomplete, taking only 8 color comparisons for the basis of it's calculations of CRI.



The sources I've found indicate that CRI compares the test light against an incan light source:

"Test Method: The CRI is calculated by comparing the color rendering of the test source to that of a "perfect" source which is a *black body radiator* for sources with correlated color temperatures under 5000 K"


----------



## blasterman (Aug 25, 2010)

> Probably because this has slightly higher lumens due to green looking brighter


 
+100 

A lot of 4100k 'Office lights' I've seen cheat a bit and add some extra red in the mix to give the bulb a slightly rosy cast. This tends to make it aethestically more pleasing than a perfectly neutral bulb. 

You have the same issue with LEDs. When you take out the excessive green of cool-whites and balance it with more amber/orange/red the efficiency plummets. Many of the high efficient neutral LEDs I've recently seen are very sterile in this respect. They trim down as much as the spectrum as posssible to get the minimum CRI and 4100k CCT.


----------



## fyrstormer (Aug 26, 2010)

StarHalo said:


> Not every space needs to be a lit like a laboratory.


Nice example. 

"Pure white" is in the vicinity of 6000K, but as StarHalo pointed out, not every situation calls for pure white light. Personally I prefer to stay in the range of 4500K-7500K (which is roughly the range from late-afternoon sunlight to rainy-day "cloudlight") because going outside of that range hurts my eyes if the light is being used for general illumination. Needless to say, I was not a big fan of the first generation of HID headlights, but fortunately they've gotten a lot better since then.

In situations where the ambient lighting is going to be dim, it's generally a good idea for the tint to be towards the cooler end of the spectrum, because the human eye isn't really designed to work with small amounts of yellow light and nothing else -- it _is_ designed to work with small amounts of blue light and nothing else, but not the other way around. I've actually been in restaurants before where the lighting was so "intimate" (i.e. illuminated with nite-lite bulbs, or close to it) that I got a headache just trying to read the menu and I couldn't wait to leave. Those places were overdoing the "warm intimate lighting" effect, but within a reasonable range of brightness, warmer light is definitely more "cozy" even if not as chromatically accurate.


----------



## fyrstormer (Aug 26, 2010)

StarHalo said:


> Right, if you're in a 3000K room, a 4500K light will look pure white. The problem is, once you move to a 6500K room, that same light will now look warm.


That's why it's better (for the purposes of the OP's question) to evaluate _ambient_ lighting itself, instead of spot-lighting inside an otherwise ambient-lit space. And in that context, 6000K is going to look like pure white, because that's what noon sunlight is, and I think we all can agree that the Sun is the ultimate ambient light source.

I have a couple flashlights with 4500K emitters in them and they always make plants look dead and wilted when I shine it on them at night. The factoid about warm-tinted LEDs neglecting the green component explains that pretty well; I'm looking forward to my forthcoming batch of Hi-CRI emitters so I can see how they look by comparison.


----------



## fyrstormer (Aug 26, 2010)

jtr1962 said:


> Humans have a built-in color balance in their brains. As a result, a fairly wide range of color temperatures look "white" once you get used to them. The real question should be what color temperature looks white to us without this automatic color balance? Speaking from experience, this is likely to be the most pleasant color temperature to live under because our brains won't be constantly trying to correct for white.


Yes, and if you pay close attention to what you're seeing, you can tell when you're compensating for the off-whiteness of the ambient lighting. I have a halogen lamp next to my desk that looks very warm compared to the fluorescents overhead, but when I look at a piece of paper on my desk that's being lit by the fluorescents, it's still apparent to me that the reflected light is somewhat warmer than "pure white". It's close enough that I can choose to ignore the difference if I want to, but I can perceive the difference nonetheless.


----------



## Twinbee (Aug 30, 2010)

> And in that context, 6000K is going to look like pure white, because that's what noon sunlight is,


I'd be wary about using the sun as a yardstick for white for a few reasons (colour temp changes throughout the day, the rest of the sky to consider, and because what we perceive as nearest true white may not be completely based on the sky/sun anyway).

I think it would be safer (though still dangerous) to base 'true white' off all visible wavelengths consisting of equal amplitude. I wonder what colour temperature that would be closest to...


----------



## fyrstormer (Aug 31, 2010)

What other yardstick could you possibly use? The Sun has been providing illumination for us since before we figured out how to build campfires.

The color temperature of _direct_ sunlight does change throughout the day, hence why I specified _noon_ sunlight, but the overall color temperature of direct+indirect sunlight doesn't change until the sun is low enough that some of the light gets scattered back into space from the low angle of incidence.


----------



## Twinbee (Aug 31, 2010)

Well, I've given two already. In summary:

1: Acclimatize test subjects to pitch black for about 10 minutes to an hour. Then let them control a wheel which adjusts the colour temperature of a light and ask them to pick what they think is nearest to true white. Get them to look at the light (dim it as appropriate). Average the results of many people and call that 'white'. I think this is the safest way.

2: Produce a light which has equal amounts of power across the whole of the visible spectrum, and call that white. This is an interesting approach, but also dangerous. It would be interesting to see if the colour temp matches (1).


----------



## jtr1962 (Aug 31, 2010)

Twinbee said:


> I think it would be safer (though still dangerous) to base 'true white' off all visible wavelengths consisting of equal amplitude. I wonder what colour temperature that would be closest to...


That would be equal energy white, or illuminant E, and it has a CCT of ~5455K ( note that illuminant E is off the Planckian locus ).


----------



## Twinbee (Aug 31, 2010)

Interesting thanks. Yes, Illuminant E is slightly more magenta/purplish than anything an incandescent light source could produce.

Another idea of representing 'true white' is the level at which the three eye cone types are equally stimulated. As far as I know, light which stimulates the eye's 'blue' colour cone also stimulates the 'red' colour cone slightly, so there may be some compensation needed.

However, even then I'd still prefer to class 'true white' as Illuminant E, and say that we all have faulty eyes


----------



## Lawliet (Aug 31, 2010)

Coming from a different angle:
Photography has the discharge of a flash tube as a de facto standard. You'd be hard pressed to find a flash in working condition thats more than 100-150k from 5600k.
To keep logistics at bay daylight films where balanced for just this color temp, the same goes for conversion filters. 
Go a step further, those flashes are the light source that was used to take all the pictures in catalogs and ads, telling us how the product is supposed to look.

Maybe not exactly scientific, but working practice.


----------



## Twinbee (Aug 31, 2010)

Interesting too. I wonder what the CRI of that flash is and how close it is to a flat spectrum.


----------



## Lawliet (Sep 1, 2010)

They are about half black body radiation, half a blend of red, green and blue spectral lines that get smeared because of the high pressure/temperature.

I haven't seen CRI measurements, but the only time someone makes a fuss about lighting selection is when some pigments are UV active.:thumbsup: Thats from people who complain if you use incans of different age in one lighting setup.


----------



## Kinnza (Oct 29, 2011)

The problem with this question is each person has a different expectation about what "true white" should be. So the first consensus about it is that there is no universal "true white", neither from an objective of subjective viewpoint.

Color perception varies from person to person, although fortunately it follows some universal paths. But the main complication is color is a multi dimensional concept. Should be "true white" about hue? In this case, a pure white should fall on the planckian locus or very close to it, say no more than 3 step McAdam ellipse and preferably, for definition, into a 1 step one (Duv<0,0007) so no any hue ("tint") is noticeable. I think in this point most people agrees. And between 3500 and 7000K.

But color has many more dimensions, and agreeing which of them is more important is way more subjective. It depends of personal preference and somewhat on the culture you have grown in. Should "true white" render colors as more similar as possible as sunlight? If so, what sunlight phase? Morning, noon, afternoon? Cloudy or clear sky? In general, most consensus along the color scientific community has been to choose sunlight like light sources, the most prominent the Illuminant D65, in which is based CIELAB, the main official (CIE) color space. But many people feels 6507K as too "cold".

It seems most people favor other dimension of color and light: its effect on our mood. Almost perfect white sources, as D65, but with a high percentage of blue white may be perfect for many people on a working space or when they want a feeling of cleanliness, but too "active" for a living room, where people prefer warmer tones so they feel more relaxed.

Another dimension of lighting is the level of light itself. This parameter is often overlooked, but it is very important. A same color of light has different effect on our mood and render colors differently as luminance level varies. Although our brain usually compensates for changes and contrast when luminance varies, it is not the same a D50 at 5 cd/m2 than at 100 cd/m2. Actually, I think many people that identifies incandescent lamps as the most pleasant white would be surprised if tries a colder tone, as 4500K but at lower luminance.

Should "true white" be pleasant or reliable on color rendering? I think the point most difficult to reach a consensus is this. Should it make scenes appear "natural" (whatever it means) or vivid, with enhanced color?

In my personal preference, I think a true white is somewhere between 4000 and 5000K, very close to planckian locus and providing a luminance matched to each application.


----------



## smarkum (May 28, 2012)

Reviving a sleepy thread. . . this caught my interest as I spend 8-10 hours a day in an office lit by 3 lamps. Initially I just put the reg. bulbs in there that were "full spectrum" 40 or 60 watt. The result was flickering . . . I work in a big office buliding so checking for the power flow to the outlets is out. So, I then tried those low watt cfl bulbs that were rated "warm". The flickering was much better , but still there. I'm VERY aware of such flickerings, a sad thing for sure! Finally I have in there two LED bulbs that use 6 watts or something like that. I'm at home now, so I cannot confim what temp the bulbs are , but I know they are warm. My goal in my office was to create warm ambiance. . . and soft lighting. I did accomplish the soft lighting part, but after reading this thread, I think I've gone overboard on the warmth scale. And, I do get headaches nearly everyday at work (I thought it was due to the nature of my work). And, I find that at certain times it seems as though the room is "foggy". I know that probably doesn't make sense, but that is how it seems by the end of the day and when my eyes and ears are REALLY tired. So I think I will get some bulbs today that are in the 4500 - 5500 range and see what diff. that makes. This has been an expensive experiment. And, considering the LED are the way I must go for less flickering, it will be even more expensive after the new bulb purchase. If anyone has any thoughts on my approach, I'd love to hear them. And, thanks for this most informative thread!


----------



## fyrstormer (May 29, 2012)

Use a halogen desk lamp. The rest of the office can be lit by flickery fluorescent bulbs and it won't matter as long as the light near your workspace is steady.


----------



## smarkum (May 30, 2012)

good info to have . . . thanks fyrstormer!


----------



## felixnauta (Feb 23, 2014)

*Re: What colour temperature is subjectively "pure white"?*



ElectronGuru said:


> My testing shows 4300K to be the mark, but 4200-4600 is close enough in most applications. 5000K is still pretty blue. 3000K is quite yellow.
> 
> One of the issues is that this scale is designed from the use of a single technology (glowing hot metal). So a non-glowing-metal source (LEDs for example) can be (measure at exactly) 4300K and still be tinted with a color not on the color temp scale, like green.



I agree with you because the question in the thread's title says: "subjectively".

And by the other hand we must to remember that "daylight" in really fact means a narrow but variety range of tone colors: at the morning tends a bit to blue; and in the evenings turns a bit to the yellow.

But the word is: "pure white" I am waiting for the arrival of some cfl's; then I will test for myself; some facts about some labels in the lamps.


----------



## markr6 (Feb 24, 2014)

*Re: What colour temperature is subjectively "pure white"?*

What really confuses me is that the 4100K T8 fluorescents in my home closets are nice and white, (but I would say too cool for living spaces). But my Zebralight neutrals 4200K and 4400K lights are completely different. If my closet lights are really 4100K, the zebralights have to be below 3000K. I couldn't imagine the tolerance to be so high.

My Fenix PD32UE torches are also very close to pure white, I'm guessing 5000K. But still a little bluish.

L10s w/ Nichia 219, PURE white (high CRI or not)


----------



## ElectronGuru (Feb 24, 2014)

*Re: What colour temperature is subjectively "pure white"?*



markr6 said:


> What really confuses me is that the 4100K T8 fluorescents...



The problem is the scale itself. Color temp is linear, 1 dimension like a long thin road. Designed to measure incan sources, its like stating your location in a small town based solely on how far along a central railroad track you are standing. 

Modern light sources are 2 dimensional, having multiple colors and other variations. A given LED or fluorescent light source can be so far away from that center, as to be meaningless. They K value is simply how close you can get to actual, on that railroad track. Distance from the track is completely ignored.


----------



## markr6 (Feb 25, 2014)

*Re: What colour temperature is subjectively "pure white"?*



ElectronGuru said:


> The problem is the scale itself. Color temp is linear, 1 dimension like a long thin road. Designed to measure incan sources, its like stating your location in a small town based solely on how far along a central railroad track you are standing.
> 
> Modern light sources are 2 dimensional, having multiple colors and other variations. A given LED or fluorescent light source can be so far away from that center, as to be meaningless. They K value is simply how close you can get to actual, on that railroad track. Distance from the track is completely ignored.



:twothumbs Got it...thanks!


----------



## fyrstormer (Feb 27, 2014)

*Re: What colour temperature is subjectively "pure white"?*

The distance away from the actual blackbody radiation line-graph isn't ignored, it's expressed as Color Rendering Index. 100% CRI means the light contains the exact radiation spectrum indicated by the color-temperature it is associated with. I don't know if 0% CRI exists, but I suppose it would mean the light has the same tint as the color-temperature it's associated with, but it's all the way at the edge of the visible-color gamut, far away from the blackbody radiation line-graph.

One example would be cyan light, which is a single color, but it *could* be labeled as 40000K with 0% CRI -- at a casual glance the overall tint of the light source might look the same, but the cyan light would be completely incapable of rendering any colors except cyan, unlike true 40000K light, which can render all visible colors, albeit with a strong bluish tint.

On the other hand, a deep red light would also be single-color, but could be labeled as 1000K with 100% CRI. That's because the dimmest blackbody radiation that people can see only consists of a narrow range of deep red light, mixed with a bunch of infra-red that we can't see, so a single-color deep red light would have the same rendering capability as true 1000K light.

If there's a problem with using blackbody radiation to rate the quality of light, it's mostly that people don't actually know what makes good light anyway, so they use hot glowing things as a benchmark, because they can instinctively relate to it.


----------



## thedoc007 (Aug 29, 2014)

*Re: What colour temperature is subjectively "pure white"?*

Subjectively, I much prefer cooler tints. Anything below 5000k looks off to me...a white sheet of paper doesn't look white any more, it is that simple. I don't care how it "feels", I just want white to look white. As phrased, it is a silly question (though it has generated some interesting comments), because to know what the subjective "pure white" color is, all you have to do is some testing on your own. No one else can tell you what your preference will be, or what color temperature you will perceive as "pure white". For me, 5500-6500k is ideal. I originally bought into the idea that it wasn't good for home lighting, but after buying several different color bulbs, and trying them out, I have changed my mind. My ideal setup is similar to how saabluster designed the Rev Captor...a couple bright 6500k bulbs, and one dimmer 3700k bulb to boost the CRI.


----------



## TEEJ (Aug 29, 2014)

There is no "color" label that is actually meaningful other than as a range.

What we CALL red, or blue or green, etc, is simply a concept, not an exact value.

For example, real colors are actually infinitely varied, and the wavelength rather than the "temperature" would be a more accurate way to describe what we CALL "color".

There are a range of wavelengths that we might consider to be be "red" for example. Which is the "real red"?

They ALL are, but, based upon our societal influences, each of us will CONSIDER a particular wavelength RANGE to be "the most red", etc.


For example, we might look at a color, and describe it as sort of a yellowish green. Why do we not have a NAME for that color, the way we have for yellow, or green? Its because we just happened to name only a few colors, and could have just as easily labelled yellowish green as yellow, or green, or blue, or ishcabible, etc.

In Greek times for example, violet was how they described some people's hair, as they had fewer names for colors, so, black hair was called violet. This makes sense, as when you look at a color chart, violet DOES tail off to what we might call black....but they didn't have black as a color label yet...it was violet. IE: Black was violet. If we asked "what's the "true violet", what would they have said? The color of a Greek maiden's hair?







We have arbitrarily labeled part of the spectrum as being "a color". We even talk about "how many colors" are in a rainbow, etc. ALL the colors are in a rainbow, but, we artificially made up "break points" that divide the infinite number of colors into groups. 

These groups do not actually exist in any physical sense of the word, other than by human consensus...and, different groups of humans have broken them down differently, so there are "colors" that people from different regions, etc, can argue about.....but, its all about the labels they each ascribed to parts of the spectrum.

To FURTHER attempt to use a color TEMPERATURE scale to describe a COLOR is going to be even more vague, as its not really about color as much as about the color at a particular time of the day for instance.


IE: There is no "color temperature" that = "pure white".


----------



## markr6 (Aug 29, 2014)

*Re: What colour temperature is subjectively "pure white"?*

I like the displays at home depot. I think they use CFLs which I don't use, but still gives you a good general idea.


----------



## AnAppleSnail (Aug 29, 2014)

Twinbee said:


> Yes, but that's just the sensory contrast of going from one situation to another. If you stick in one enviroment, then there should be a colour temperature that's closest to what most people would consider pure white (as you imply yourself afterwards).



Millennia of experience deny a constant environment. Sunlight ranges from 3000 to 7000K CCT, depending on conditions (Sunset, overcast, noonday, etc). You're looking for something that's not possible.

Look for a light source between 3000K and 5000K (Higher CCT for work-like tasks, lower for relaxing tasks), with good color perception card results. R9 is a weak point for LEDs and arc lamps - It's a delicious red. The blues are weak for hot filaments.


----------



## SemiMan (Aug 30, 2014)

Lots of conjecture on this thread but the LRC did a study and found within the study group that almost without exception people picked 4000k as white +/- a few hundred k after adaptation.


----------



## ElectronGuru (Aug 31, 2014)

I did my own study and found it to be 4300, within the range above:

http://www.candlepowerforums.com/vb/showthread.php?232038-Flashlight-Tint-Color-Reference


----------



## fyrstormer (Sep 1, 2014)

4300K is significantly warmer than pure white to my eyes. 6000K is pure white to me, but I prefer 5000K because I like just a teensy bit more yellow in my light.


----------



## recDNA (Sep 1, 2014)

fyrstormer said:


> 4300K is significantly warmer than pure white to my eyes. 6000K is pure white to me, but I prefer 5000K because I like just a teensy bit more yellow in my light.


That's my preference as well. I don't enjoy brownish yellow light. Some people clearly do. Ideally you want a complete spectrum but led's cannot do that as I understand it. One thing I know. I find greenish light intolerable but I'm told some hunters prefer it.


----------



## SemiMan (Sep 1, 2014)

The study was not about preference but about what light when dark adapted looked most "white".

In terms of preference under the black body ... Was the preferred color point at all CCTs in another study.


----------



## markr6 (Sep 2, 2014)

fyrstormer said:


> 4300K is significantly warmer than pure white to my eyes. 6000K is pure white to me, but I prefer 5000K because I like just a teensy bit more yellow in my light.



Can't believe what I'm hearing?!?! :hairpull: It's amazing how different everyone is on this subject. Also can't believe peoples eyes can be so different from another.

But consider just my own eyes. When look out of just my left eye, it's like looking thru a warming filter. Just my right eye is like cooling filter. Very strange. This is more apparent when outside looking at landscapes, trees, sky, the road, etc. The difference is even more exaggeated with sunglasses on.


----------



## Bullzeyebill (Sep 3, 2014)

markr6;4502When look out of just my left eye said:


> Have you considered a cataract issue with one eye? I recently had cataract surgery on L eye, and now everything is brighter.
> 
> Bill


----------



## fyrstormer (Sep 3, 2014)

markr6 said:


> Can't believe what I'm hearing?!?! :hairpull: It's amazing how different everyone is on this subject. Also can't believe peoples eyes can be so different from another.
> 
> But consider just my own eyes. When look out of just my left eye, it's like looking thru a warming filter. Just my right eye is like cooling filter. Very strange. This is more apparent when outside looking at landscapes, trees, sky, the road, etc. The difference is even more exaggeated with sunglasses on.


Oh, but they are. Everyone's retinas have different densities of red, green, and blue cones, and everyone's brains are more or less sensitive to inputs on those three channels. Some women have four-color vision, too, because they have two types of green cones, each one coded-for on one of their two X chromosomes.


----------



## SemiMan (Sep 3, 2014)

-----


----------



## markr6 (Sep 3, 2014)

Bullzeyebill said:


> Have you considered a cataract issue with one eye? I recently had cataract surgery on L eye, and now everything is brighter.
> 
> Bill



No, but I did have a thorough exam just 2 weeks ago and everything was fine. I vaguely remember doing the standard test optomologists do when I was a kid, looking thru a book with "hidden" numbers in various colors. I think he said there was a very slight issue distinguishing certain colors, but haven't had a problem. Could have something to do with color temperatures...who knows.


----------



## KITROBASKIN (Sep 3, 2014)

*Re: What colour temperature is subjectively "pure white"?*

Thanks to felixnauta for bringing this thread to the present.

The word 'subjective' allows some flexibility here. I used to consider the white-is-white standard to be the be-all-end-all of tint preference. Now I use another subjective metric:

Going outside when the light of the sun has the most pleasing cast (for me it is about 1/2 to 1 1/2 hours after sunrise) and finding an area of exposed dirt on the ground that is in partial shade (but one can also use the shadow made from your body). Now, shine your lights on the shadowed part of the dirt near dirt that is lit by the sun. Green plants and other objects don't look quite so 'off' as the medium brown dirt we have here, under the light of a flashlight.

Cool white looks washed out and dull. Warm white and 'neutral' XML2's look yellow. The SkyLumen SL-1 XML2 dedomed neutral looks kind of bluish green. The ZebraLight SC62d is close to the sun's tint but a little grey with maybe a tiny smidge of green. What looks the closest to early morning sun? For me it is the MBI HF Nichia 219A. 

At night, it is the dirt around where I live that is the most distractingly off color under the light of a flashlight, and the Nichia makes the dirt look darker and 'richer'. But the sunlight test really shows how nice the Nichia is. I'm wondering how the 219B ~5000K looks?


----------



## markr6 (Sep 3, 2014)

*Re: What colour temperature is subjectively "pure white"?*



KITROBASKIN said:


> I'm wondering how the 219B ~5000K looks?



I like the 219B in my L10C. It's on the cool side though. While I think it makes colors more accurate, I prefer the warmness (slight red tint) of the 219A. And I would say the 218B is pretty close to the SC62d.


----------



## fyrstormer (Sep 3, 2014)

SemiMan said:


> Yet anytime testing is done except for the obvious outliers most people test surprisingly similar.


If you really believe that, you need to look up the definition of "confirmation bias". Even scientists are susceptible to it, but when common people like us get our hands on the data, confirmation bias basically bulldozes anything resembling an accurate interpretation of the data. I don't know how many times I've seen someone start a thread on CPF about an article that "proves" their own personal preference is the default for humanity, whether it's warm-tinted white light or red night-vision light or whatever. The arguments ALWAYS go something like this: "I just read an article stating that humans are 'programmed'/'adapted'/'designed' to prefer a certain type of light. Don't argue with me, it's totally true! Look, I have numbers! Do you have numbers? No? Well, that proves my preference is based on fact and other people's preferences are based on opinions." Arguments like that aren't even logical enough to be wrong.

Thank you and goodnight.


----------



## SemiMan (Sep 3, 2014)

-----


----------



## thedoc007 (Sep 3, 2014)

SemiMan said:


> Scientific studies can only result in confirmation bias if the outcome is one that is generally known or accepted. That absolutely is not the case in this study.
> 
> People also like to keep believing what they believe even proven not true.
> 
> ...



The whole idea of a study to figure out what is "subjectively" pure white is a joke. Even if most people think it is 4300k (I haven't read the study and can't say either way) that doesn't really mean anything. It isn't like someone else's opinion is a predictor of your own opinion...you can't generalize to a population at all, since it is by definition an individual perception. If you want to know what is subjectively pure white, just announcing your own opinion has exactly the same scientific value, i.e., none.


----------



## SemiMan (Sep 3, 2014)

[-----


----------



## thedoc007 (Sep 4, 2014)

SemiMan said:


> The study was not about preference but about what light when dark adapted looked most "white".
> 
> In terms of preference under the black body ... Was the preferred color point at all CCTs in another study.





SemiMan said:


> And here we go, yet another person clueless about the study making a conclusion on it. Your point is what?



Care to provide a link to the studies you are talking about? I just read the thread again, and the only reference to a specific study was to one by the "LRC". Don't know what that is...the link in the OP to a page about HID and "pure white" perception was not a study at all, as far as I can tell. And nothing was listed about the methods they used...

Maybe we are just talking about two different things...I've just been responding to what has been linked to and discussed in the thread...if you have an actual scientific study to reference, that link is long overdue.

My point is simply that you cannot assume that just because one study finds "pure white" (a nebulous term, at best) to be a certain temperature, doesn't mean that you can assume other people will agree. As many posts have already discussed, changing any of a number of parameters in the test can dramatically skew results. And given that it is a matter of opinion anyway, a study cannot PROVE something that is subjective. 

If you have a reference, I would definitely be interested, perhaps it will change my mind on the matter. But just repeating yourself, and saying people are ignorant or clueless, is not really adding much to the discussion.


----------



## Bullzeyebill (Sep 4, 2014)

thedoc007 said:


> Care to provide a link to the studies you are talking about? I just read the thread again, and the only reference to a specific study was to one by the "LRC". Don't know what that is...the link in the OP to a page about HID and "pure white" perception was not a study at all, as far as I can tell. And nothing was listed about the methods they used...
> 
> Maybe we are just talking about two different things...I've just been responding to what has been linked to and discussed in the thread...if you have an actual scientific study to reference, that link is long overdue.
> 
> ...



I concur, please keep the conversation polite.

Bill


----------



## fyrstormer (Sep 4, 2014)

So, I just noticed this thread is 4 years old. Probably time to retire it.


----------



## Bullzeyebill (Sep 5, 2014)

fyrstormer said:


> So, I just noticed this thread is 4 years old. Probably time to retire it.



No

Bill


----------



## donjoe (Sep 5, 2014)

lyyyghtmaster said:


> Or notice this: even in the early morning, before the sun rises, the skylight does a surprisingly good job of rendering wood tones, even compared to our "neutral" artificial sources! And golly, that skylight has to be 20 000 K or more! Sure the spectral power distribution is skewed heavily towards the blue. But since it's coming from a mostly-continuous-spectrum incandescent source, the deeper red is still present in significant amounts!


I would submit rather that the reds are well represented because 20 kK is well into the violet section of the spectrum, where it's nearing red again.


----------



## SemiMan (Sep 5, 2014)

-----


----------



## donjoe (Sep 6, 2014)

SemiMan said:


> I would submit that it is probably no where near 20K CCT. That only occurs under heavily clouded skies.


I don't know about that. There's an undeniable presence of violet frequencies in the early morning twilight that's inconsistent with low color temperatures.
http://www.superhqwallpapers.com/2560x1600-high-quality-wallpapers/twilight-morning-2560x1600/


----------



## Twinbee (Dec 10, 2014)

Wow, plenty of posts since I've been away!

Thanks Bill for not closing the thread. I doubt I could get as much insight and enthusiasm about the topic anywhere else, no matter how hard I looked, and a definitive conclusion is still somewhat out of sight.

The question "What do people consider the most 'white'?" is different than what they consider the most 'pleasant' for everyday lighting which is also a very interesting question. Perhaps someone else can start that other question.



> As phrased, it is a silly question (though it has generated some interesting comments), because to know what the subjective "pure white" color is, all you have to do is some testing on your own.



I know colour 'experiencía' will differ slightly from person to person, but we can still get an average for everyone. And testing for yourself won't yield an accurate answer since people find it difficult to test for these sort of things. It's like asking how heavy a particular bag of rice is, or how many lumens a particular bulb produces. We can get close, but significant error is possible, especially if you've just exited a previous room and entered a new room with a different white where the contrast itself produces bias. The shade of wallpaper, carpet and furniture produces further bias so you have to be extremely careful.



> Even if most people think it is 4300k (I haven't read the study and can't say either way) that doesn't really mean anything.



The reason why it's useful is because offices and shared spaces can set the lighting to the 'averaged' hue. Also monitor displays can use the hue as default white. It not only means something, but is extremely practical too.



> For example, real colors are actually infinitely varied, and the wavelength rather than the "temperature" would be a more accurate way to describe what we CALL "color".



Well if you want to go down that route, even the spectrum won't yield the colour magenta which is a mix of red and blue.

Without going into mega-complicated 3D models of colour, a representation using RGB (red, green and blue) would suffice for 99% of people. Just a pity that monitor displays don't standardize on this, and white appears different on my laptop than my 26" monitor or 32" TV.



> Lots of conjecture on this thread but the LRC did a study and found within the study group that almost without exception people picked 4000k as white +/- a few hundred k after adaptation.



Excellent - just what I wanted! Like thedoc007 said, can you give me a link?


----------



## Noctiluco (Dec 10, 2014)

3800-4000k is very good white


----------



## SemiMan (Dec 10, 2014)

No need for either conversation ... Both have been researched


----------



## Twinbee (Dec 10, 2014)

Link us up then


----------



## thedoc007 (Dec 10, 2014)

SemiMan said:


> No need for either conversation ... Both have been researched



If you have actual studies and research, please share it. I asked three months ago for you to provide some documentation, or even a starting place so I can look for myself. But still nothing...


----------



## markr6 (Dec 11, 2014)

I still say visit a Home Depot and look at their display for a good general idea. Keep in mind some stores may vary, but can't say for sure. They also used some CFLs, so CRI aside...

*Soft White- 2700K | Bright White - 3500K | Natural Daylight - 5000K*

The soft white is very close to the incandescent. I find it hard to believe anyone would argue against the 3500K being the most neutral. And there's nothing "natural" about the natural daylight 5000K in reality. Maybe in some sophisticated computer model, though.


----------



## SemiMan (Dec 11, 2014)

-----


----------



## SemiMan (Dec 11, 2014)

-----


----------



## Twinbee (Dec 11, 2014)

Semiman, can you not find the study? Me and maybe thedoc will continue to bug you until you link it or at least until you give up searching for it =p

So you say it's 4000K for the the 'subjectively whitest' light right? What is it for the subjectively most pleasant white?


----------



## markr6 (Dec 11, 2014)

SemiMan said:


> Can't review bulbs in a store. You eyes are adjusted to store light, not the light you will be installing. Rough idea is what you get which is better than nothing.



No I did just fine. That's like saying you can't choose a bulb inside your home since your eyes are adjusted to the sunlight, sunset, TV, glow from smartphone, etc. I guess technically you may be right, but that's splitting hairs. I looked at the bulbs in HD, and decided 3500 was the perfect temp for me. It didn't change when I got home.

It also helps they are isolated in those little boxes, not just plugged into a wall somewhere.


----------



## thedoc007 (Dec 11, 2014)

SemiMan said:


> Can't review bulbs in a store. You eyes are adjusted to store light, not the light you will be installing. Rough idea is what you get which is better than nothing.



On this point I concur with SemiMan. Certainly you can get some idea...but the store lighting does give you a baseline which COULD skew your preference pretty badly, especially if you were unaware of it. 

I know that if I have been using a cool source for a while, warm tints look extremely yellow. But that exact same tint can look fairly neutral white if you have been accustomed to it. That's why I think the "pure white" phrase is problematic. Depending on how you set up the experiment, you could quite easily get whatever results you want. And someone else using another method could find a very different result. Since no one is forthcoming with any actual studies, though, it may be a moot point.


----------



## Twinbee (Dec 12, 2014)

> That's why I think the "pure white" phrase is problematic.



I agree with the difficulties in removing sources of bias.

However, you can adjust for these kind of things. For example, you can stay in a dark room for an hour before seeing the light.

Bear in mind that no matter how long I stay in a room with say a 2000K or 12000K light, I'll (and I bet you) would always see a orange/red (former) and blue/violet (latter) light. Less so with 4000K and say 7000K, but still noticeable.


----------



## thedoc007 (Dec 27, 2014)

Bump. Still waiting for a link or source for ANY scientific research on the subject.


----------



## brickbat (Dec 28, 2014)

thedoc007 said:


> Care to provide a link to the studies you are talking about? ...
> 
> If you have a reference, I would definitely be interested, perhaps it will change my mind on the matter. But just repeating yourself, and saying people are ignorant or clueless, is not really adding much to the discussion.



Yes. If a poster is relying on a scientific study, please share it with the rest of us...


----------



## Anders Hoveland (Mar 5, 2015)

*Re: What colour temperature is subjectively "pure white"?*



ElectronGuru said:


> My testing shows 4300K to be the mark, 5000K is still pretty blue.



I agree. I believe moonlight is about 4200K. 
4500K is a good cool neutral white. 



StarHalo said:


> There is no pure white; you're always going to bias one light source against another, so if you're been in 4300K lighting and move to 6500K, it'll look cold, if you've been in 8000K lighting and move to 6500K, it'll look warm, etc.


It is certainly true that your eyes adjust, and it's easy to forget that you are viewing things under 2800K orange-tinted light. But I believe a person can still tell the difference, if they step back and take a moment to think about what color the light source actually is. Color bias is mostly a subconscious thing. The color of the light will definitely seem different, but I think it is still possible to know and see it for what it is.


----------



## thedoc007 (Mar 5, 2015)

*Re: What colour temperature is subjectively "pure white"?*



Anders Hoveland said:


> But I believe a person can still tell the difference, if they step back and take a moment to think about what color the light source actually is. Color bias is mostly a subconscious thing. The color of the light will definitely seem different, but I think it is still possible to know and see it for what it is.



The science would suggest that you can't always (often?) see what is...there are multiple layers of perception/interpretation. 

http://www.ted.com/talks/beau_lotto_optical_illusions_show_how_we_see


----------



## NoNotAgain (Mar 5, 2015)

*Re: What colour temperature is subjectively "pure white"?*

I've seen numerous postings stating that 5500 Kelvin is cool white. Cool white is above 6500 Kelvin.

In the photographic world, 5600 Kelvin is day light full sun temperature. This chart is from one of the major photographic filter manufacturers, Lowel/Tiffen. http://lowel.tiffen.com/edu/color_temperature_and_rendering_demystified.html


----------



## SemiMan (Mar 8, 2015)

*Re: What colour temperature is subjectively "pure white"?*



NoNotAgain said:


> I've seen numerous postings stating that 5500 Kelvin is cool white. Cool white is above 6500 Kelvin.



As there is no standard, your's is just an opinion much like anyone else.

As we are talking lighting, the concept of warm/cool came from fluorescent lighting as it was the first light source that had tailorable white. The first "cool white" was 4000k, and 5500 daylight with some variant on the daylight name for 6500 and 3000K as warm white.

As LED people were not often lighting people they adopted the readily understood warm for 2700-3000, but when they only had 5500-6500K ish at the top end, they called that cool white. Later when they came out with 4000, they adopted neutral white which was pretty a new term in lighting at that point though may be some other references.


----------



## Anders Hoveland (Mar 17, 2015)

*Re: What colour temperature is subjectively "pure white"?*



NoNotAgain said:


> I've seen numerous postings stating that 5500 Kelvin is cool white. Cool white is above 6500 Kelvin.


I do not see how anyone can think 5000K is not cool white, but everyone is different apparently.



NoNotAgain said:


> 5600 Kelvin is day light full sun temperature.


It's important to recognise the distinction between "sunlight" and "daylight". Sunlight is the light coming directly from the sun, after being attenuated through the atmosphere. Daylight also includes the background light from the sky, the addition of which substantially alters the correlated color temperature.


----------



## chenrazee (May 8, 2017)

StarHalo said:


> I should complete the sentence as follows: "Right, if you're in a 3000K room, a 4500K light will look pure white. The problem is, once you move to a 6500K room, that same 4500K light will now look warm." So there is no one color temp you can make a flashlight that will look white even a majority of the time, because the environment you're using it in is always changing.
> 
> As for lighting your house, you have to be careful with how cool you get, otherwise it just looks like you're lighting your living room with garage worklights; there needs to be a bit of warmth to house lighting to prevent it from looking too sterile. I find ~3500K works nicely in office and bathroom lighting, and ~3000K is about right for bedrooms and living rooms.



FWIW, the Twilight app on android defines 1000K-3500K as Relaxing and 4000K-5000K as Energizing. This fits with the concept of warmer colours in places we relax in (bedroom, lounge, dining room) and cooler colours in places we work in (kitchen, study/home office, garage/shed).


----------



## wus (Jan 12, 2020)

For me it's white when I come from the sunlit outdoors into a house and the light there matches the outside light. 

When the tungsten halogen bulb in the entrance to our house failed (a couple years ago) I looked for a bright LED source with high CRI and daylight color. The closest I found (and wanted to afford) was specified with 5000K. This still shines a little bit warmer than the direct sunlight out the door, so I conclude the "precise" white must have a somewhat higher color temperature. This also conforms to school book knowledge, that says a neutral white is around 5500K or 5600K.


----------



## twistedraven (May 6, 2020)

If you were to take into consideration spectral balance from an ideal black body source, then 5400k would have the most balanced spectral response-- being objectively closest to a pure neutral white.

However in artificial lighting like LEDs, there's always dips in cyans, deep reds, and spikes in blues. 

Now with the objectivity out of the way, it's literally impossible to specify a pure neutral to human perception, because we are by nature, subjective to a core. There will always be relations at play, there will always be 'light a is cooler or warmer than light b', or 'light c is in between a and b in temperature.'


----------



## DayofReckoning (May 6, 2020)

I guess one's own perception can play a pretty big role. I have noticed how my own perception of color temperature can change a lot once I use a certain light for a bit, then swap over to another.

For example, when only using my incandescent A2, it's 3350K beam appears almost pure white to me. However, after switching over to a 5000K LED light for a bit, then swapping back to the A2, the A2 will now appear yellowish in color to me. 

I don't know what the answer to the OP's question is, but from an LED, 4500K to 5000K appears closest to pure white _*to me. *_


----------



## maxx44 (Jun 11, 2020)

> I still say visit a Home Depot and look at their display for a good general idea. Keep in mind some stores may vary, but can't say for sure. They also used some CFLs, so CRI aside...
> 
> 
> Soft White- 2700K | Bright White - 3500K | Natural Daylight - 5000K
> ...



That's true, 3500K is the most optimal and neutral brightness level. Temperature adjustments is a great and useful thing in such situations, when you're using your thermal binoculars as well. I've recently purchased model AGM Explorator TB75-384, from here ( resource: https://www.agmglobalvision.com/thermal-imaging/thermal-binoculars ), and my basic knowledge about temperature levels helped me a lot with adjustments.


----------

