Why warm tint is more preferred in flashlight, scientific explanation

[h=1]Kruithof curve[/h]

Named after the Dutch physicist Arie Andries Kruithof,[2]​ the Kruithof curve relates the illuminance and colour temperature of visually pleasing light sources. Lighting conditions lying inside the bounded region were empirically assessed as being pleasing, whereas conditions outside the region were displeasing.
The colour sensation of a given light mixture may vary with absolute luminosity, because both rods and cones are active at once in the eye, with each having different colour curves, and rods taking over gradually from cones as the brightness of the scene is reduced. This means, for example, that light with a colour temperature of 6000 K may appear white under highluminance, but appear bluish under low luminance. Under the same low luminance conditions, the colour temperature may need to be adjusted to, say, 4700 K, to appear white. This effect leads to a change in colour rendition with absolute illumination levels that can be summarised in the empirical Kruithof curve.[3]​
As the brightness of the scene decreases, the brightness of red colours decreases more rapidly than those of blue colours, this being the Purkinje effect.




[url]http://en.wikipedia.org/wiki/Kruithof_curve


http://en.wikipedia.org/wiki/Purkinje_effect[/URL]

You are making an erroneous assumption that people DO prefer warm tints. I know many who do not...

shane45_1911 said:

You are making an erroneous assumption that people DO prefer warm tints. I know many who do not...

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+1 on your quote.I bought a warm tinted light after hearing great things about them on CPF,try as i might i just can't get away with the tint & i do
prefer a cool white tint over the warm tints.I know warm tints will be to the liking of a lot of people but for what i use my lights for i don't have any
advantage for them.I guess everyone is different though & it's up to everybody to choose what they spend there money on.happy christmas .

I do find that I don't like very cool lights in very dark conditions. I don't like really warm tints at all though. I bought an LED light bulb for my house rated 2700k and I really don't care for it.

I think between 3500k and 4500K is ideal for most artificial lighting

FYI warm does not mean high CRI

Named after the Dutch physicist Arie Andries Kruithof, the Kruithof curve relates the illuminance and colour temperature of visually pleasing light sources. Lighting conditions lying inside the bounded region were empirically assessed as being pleasing, whereas conditions outside the region were displeasing.

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It is impossible to form a scientific conclusion about opinions. For example: I don't like warm-tinted flashlights, therefore Mr. Kruithof's work is completely invalid. See? It's too easy to disprove a scientific conclusion based on opinions, because all I have to do is disagree.

Neutrals are a good compromise and keep people from both camps reasonably happy in a pinch if needed

The poster is not saying that is scientifically proven that people prefer warmer tints, but that their preference shift towards warmer tints as illluminance level decreases. And that is due the Purkinje effect, which is well proven.

Meaning that if you like a given tint at high illuminance (being warm or cool), usually people find more pleasant a warmer tint at lower illuminances. As flashlight often provides low illuminances, it mean usually people find warmer tints more pleasant, as compared to the tint they prefer at higher illumination levels (fixed lighting, usually). Of course, preference is subjective and analyzed by statistical tools, so it dont mean you will prefer a warmer tint under lower illuminance, but a majority of people does.

What is more objective is to say you need a larger saturation in the red as illuminance decreases in order to keep good contrast and discrimination ability. At the time of Kruithof that automatically mean a warmer light, but with LEDs it is not necessarily so, or it may be at way lower shift in CCT. Spiky spectrums may provide good contrast and color appearance without the need of moving all the spectrum to the red.

I would say that at the light of LEDs, actually the meaning of Purjinke effect is we need spectrums with a sharp peak in the red when using flashlights in order to keep similar discrimination ability under reduced illuminance. Of course blue is too required for contrast, but fraction of blue in the spectrum can be a little lower because our relative sensibility to blue increases under low illuminance.

BTW, when going below photopic conditions due low illuminance, brightness perception (lumens) change, as do color rendering, so color indexes, as CRI, becomes not meaningful.

fyrstormer said:

I don't like warm-tinted flashlights, therefore Mr. Kruithof's work is completely invalid.

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No. Mr. Kruithof never stated, that everyone without exception fits into his scheme. Only that the majority of people does.

From a functional standpoint I think Cool is somewhat better simply because it appears more aggressive and blinding and also seems to output a bit more.

The preference of Kelvin goes up with increased lux,
If you find your self liking a light with 3000K warm tint, it could be that light might not be bright enough.
On group average & not individual basis, the dimmer the flashlight, the more preference toward warm tint it will be.

I did a TINY bit of experimenting with light colors awhile back.

I found that my cooler light, made things seem sharper to MY eye, when viewing things around concrete.
Maybe it was the bluish grey of the concrete that worked well with the cooler light.
Who knows?!

Maybe there is a thing, where a particular colored light, renders analogous colored items, clearer.

But on reading the following, well, I think I'll try a few more things and see what pans out ---

ma_sha1 said:

The preference of Kelvin goes up with increased lux,
If you find your self liking a light with 3000K warm tint, it could be that light might not be bright enough.
On group average & not individual basis, the dimmer the flashlight, the more preference toward warm tint it will be.

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Spacemarine said:

No. Mr. Kruithof never stated, that everyone without exception fits into his scheme. Only that the majority of people does.

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I find that hard to believe he talked to the majority of people on the planet and got their preference on cool or warm lights in order to back up this hypothesis.

I can't say that the curve proves that warm tints are preferred since it's based on opinion. (Also, is a "pleasing" tint necessarily better?) However, I can say that it does probably show that for lower lighting levels, a slightly lower color temperature than one's preferred tint may be ideal.

(Also, I find that enough people don't like incans like a minimag 2aa with dying cells because it's too orange. Doesn't this go somewhat against what the curve suggests?)

Kinnza,

Thank you for that lucid explanation of the Kruithof phenomenon. It is commonly misbelieved that preference and opinion are the same thing. They are not. It is possible to formulate a theory that describes how things work from empirical investigations of preference. This is what the Kruithof and Purkinje phenomena speak to. For example in marketing research, psychology, vision and perception. Preference can reveal insights into underlying aspects of the organism and its function. Opinions can be either informed or unexamined evaluations of something.

In other words, opinions are like, well, you know, everybody's got one. Preference in this context, however, is related to aspects of typical functioning of the human visual system. That one can "learn" to like a warmer or a cooler tint is beside the point. It is a result of experience and exposure. What Kruithof and Purkinje speak to in this case is something fundamental to perception and processing, something in the hardware and how the wetware interacts with it.

Wilkey

This is an interesting article (is linked off the Wiki above):

Daylight: Is it in the eye of the beholder? by Kevin P. McGuire

http://www.soluxtli.com/edu13.htm

hoongern said:

(Also, I find that enough people don't like incans like a minimag 2aa with dying cells because it's too orange. Doesn't this go somewhat against what the curve suggests?)

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Part of the reason they don't like the orange color from a MiniMag is that they know from experience that darkness looms all too soon in that situation.

I find that warm tint leds look artificially brown, much prefer neutral tints.

I thought that I'd just add a reason why I don't think the Kruithof curve proves anything regarding warm tints being better - It's just a study of how a particular light source changes as the light intensity goes down: given a light source of given intensity and color temperature, if we are to lower its intensity, its CCT should also go down to look "the same".

This is simply a study of correlation between intensity level and CCT to produce similar looking lighting.

However, you can't say that the curve shows that warm tints are better than cool tints. If you wanted to say so, I could argue that the curve shows that cool tints are good, since above 450 lux (which more of our lights are) - the curve shows CCTs all the way to 7000K (VERY cool white) as being 'pleasing'. (I'm not saying this is the case, just showing that the Kruithof curve doesn't say warm is better than cool in any way, vice versa)

fyrstormer said:

It is impossible to form a scientific conclusion about opinions.

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Impossible to form conclusions, but still helpful in understanding psychological processes behind why some of us make certain choices which seem to change with additional external variations, and as such this thread is helpful, particularly because it doesn't suggest, as many seem to be assuming, that warmer is better, but just that there are certain scientific factors at work that many have not realized previously.

mikedeason said:

From a functional standpoint I think Cool is somewhat better *for me* simply because it appears more aggressive and blinding and also seems to output a bit more.

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I made a tiny addition to your post to improve it's accuracy, as there are many of us who don't prefer aggressively blinding lights. Your point is quite valid, but it's still not going to cover all of us.

ma_sha1 said:

The preference of Kelvin goes up with increased lux,
If you find your self liking a light with 3000K warm tint, it could be that light might not be bright enough.
On group average & not individual basis, the dimmer the flashlight, the more preference toward warm tint it will be.

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While I'm mostly in agreeance with you, I happen to also like cooler tints on lower levels if they are coming from a floody light with a smooth beam pattern.

I've been wondering about this for a while. I prefer a 5-6k light, but I'm red green color deficient. I wonder if that affects my preference.

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