Discussion:
Preferred lighting colour temperatures in South Europe and Asia
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Ingo Thies
2014-04-11 11:48:24 UTC
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Dear all,

maybe this topic has been discussed here earlier (and in times where
this groups had been more 'alive'): What is the reason for the
preference of higher colour temperatures (CCT) in the southern Europe or
Asia relative to Central or Nothern Europe?

The naive but probably wrong answer sometimes given in the web (without
any reference, though) is, that higher CCT look "cooler" and thus makes
people sweat less at subtropical or tropical temperatures while lower
CCTs make people feel "warmer" in cooler countries.

In my opinion, this explanation doesn't hold water. First, it could not
be reproduced in own experiments and is also not plausible anyway since
it mixes up two completely different effects: the
psychological/synesthetic effect of colour on the one hand, and physical
excess heat the body needs to get rid off on the other. Consequently,
using blueish white light in summer doesn't replace sweating or air
conditioning (or swimming :)) but rather has no noticeable effect on the
subjective warmth. Physically, I would expect just the contrary effect:
Blueish light suppresses melatonin and rises the blood pressure like
coffee, which might be a disadvantage in a hot climate. But in polar
regions, high CCT colour in the morning and during the day may partly
replace the under-abundant sunlight.

Moreover, the preference of neutral or daylight CCTs is found in entire
Asia, even in the cooler climates there, so the "warmth" argument
doesn't apply there.

My suspicion is rather that in southern countries as well as in Asia
fluorescent light has been adopted much earlier than in northern or
central Europe or the U.S. where incandescent light has long been
standard. Since low CCTs weren't widely available for fluorescents at
that time people simple got used to white light.

Are there any independent studies on this topic?

Ingo
Andrew Gabriel
2014-04-12 10:33:04 UTC
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Post by Ingo Thies
Dear all,
maybe this topic has been discussed here earlier (and in times where
this groups had been more 'alive'): What is the reason for the
preference of higher colour temperatures (CCT) in the southern Europe or
Asia relative to Central or Nothern Europe?
The naive but probably wrong answer sometimes given in the web (without
any reference, though) is, that higher CCT look "cooler" and thus makes
people sweat less at subtropical or tropical temperatures while lower
CCTs make people feel "warmer" in cooler countries.
In my opinion, this explanation doesn't hold water. First, it could not
be reproduced in own experiments and is also not plausible anyway since
it mixes up two completely different effects: the
psychological/synesthetic effect of colour on the one hand, and physical
excess heat the body needs to get rid off on the other. Consequently,
using blueish white light in summer doesn't replace sweating or air
conditioning (or swimming :)) but rather has no noticeable effect on the
Blueish light suppresses melatonin and rises the blood pressure like
coffee, which might be a disadvantage in a hot climate. But in polar
regions, high CCT colour in the morning and during the day may partly
replace the under-abundant sunlight.
Moreover, the preference of neutral or daylight CCTs is found in entire
Asia, even in the cooler climates there, so the "warmth" argument
doesn't apply there.
My suspicion is rather that in southern countries as well as in Asia
fluorescent light has been adopted much earlier than in northern or
central Europe or the U.S. where incandescent light has long been
standard. Since low CCTs weren't widely available for fluorescents at
that time people simple got used to white light.
Are there any independent studies on this topic?
In the parts of Europe I've visited, I do not recall seeing the trend
you are suggesting. I generally find that the CCT is matched to the
lux levels roughly guided by the Kruithof curve. In homes, lighting
levels tend to be low, possibly unconsiously set at levels where the
2700K filament lamps matched the Kruithof curve, and home CFL's
follow this, both because it still feels right and because it matches
filament lamps still in use. Where higher lux levels are used such as
offices and circumstances where you are supplementing natural daylight,
then higher CCT is used, again roughly matching Kruithof curve, but
probably also because a 2700K source mixed with natural daylight would
look a bit strange.

I doubt that the lux level from most artificial lighting is sufficient
to significantly impact melatonin, unless you are sitting a couple of
feet from a SAD light, where I thought it had been shown that the high
CCT "specially expensive" tubes had no advantages over any other tubes.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
Ingo Thies
2014-04-12 11:58:29 UTC
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Post by Andrew Gabriel
In the parts of Europe I've visited, I do not recall seeing the trend
you are suggesting.
I haven't yet visited private homes in South Europe, but I have talked
to people coming from Asia (e.g. from China) who confirmed that not only
white light (4000-6500 K) is preferred there but also the relation of
yellowish light being "warm" and blueish being "cold" seems to be
unknown there.

But even after long searches with Google and other search engines I
couldn't find any useful scientific study on this topic. Not even the
widespread color-warmth relation seems to be explained scientifically;
the classical interpretation of reddish warm fire vs. blueish cool water
does not seem to hold water since the color-warmth-relation of sunlight
is just the opposite (the stark white noon sunlight is perceived as
being much hotter than the reddish light of the rising or the setting
sun), so 2700 K should referred as "cool evening light" while >5000 K
being called "warm noon light" and 6000+ K "tropical light".
Post by Andrew Gabriel
I generally find that the CCT is matched to the
lux levels roughly guided by the Kruithof curve. In homes, lighting
levels tend to be low, possibly unconsiously set at levels where the
2700K filament lamps matched the Kruithof curve, and home CFL's
I doubt that the old Kruithof relation is still valid today. I have read
some articles about that (I can try to retrieve them again) where the
Kruithof curve could not be reproduced.

In today's lighting market there is essentially no degree of freedom to
the consumer to make any adaption since retail stores in Germany only
offer 2700 or even 2500 K CFL and LEDs. Sometimes you might still get
one with 3000 K, but for higher CCT you need to search the online stores
for something fitting.

In other words: The typical consumer market, where most peoble buy their
bulbs, does not offer any variety but only "warm white" monoculture.
This prevents people from getting used to other color temperatures than
incandescent/halogen and thus rules out any unconscient preference.

A possible explanation for Kruithof's relation could be the apparent
blue shift of human vision in lower light levels. At broad daylight
(several 1000 to 100,000 lux), neutral white is something around
6000-7000 K. For lux levels typical for residental homes (around 100
lux) the neutral white point shifts to about 3500-4000 K. The reason
might be a combination between the Purkinje shift (caused by the
lux-dependent different sensitivity curves of rods and cones) and some
evolutional "white balance algorithm" in the visual cortex.

I can conform this relation and therefore prefer 5000-7000 K as working
light or in the morning, but between 3000 and 4000 K in the evening,
both looking approx. "white". 2700 K, on the other hand, is never
perceived as white although we are still able to interpret surface
colors correctly (e.g. like identifying people's walk directions at the
train platform while you are sitting in a slowly movine train).
Post by Andrew Gabriel
I doubt that the lux level from most artificial lighting is sufficient
to significantly impact melatonin, unless you are sitting a couple of
feet from a SAD light, where I thought it had been shown that the high
CCT "specially expensive" tubes had no advantages over any other tubes.
To my knowledge, even light of 5 lux or more can cause sleep problems,
and recent studies presented on "Deutschlandfunk" radio suggests that
even the 0.2-0.3 lux of the full Moon could cause trouble to some
people. On the other hand, to fully suppress melatonin (and thus
treating SAD) you need several 1000 lux. There seems to be a wide range
from "too bright to sleep" to "too dim to feel happy".

But I agree that the impact of color temperature to sleep problems is
often exaggerated. A 6500 K LED or D65 has only about 2-3 times more
melatonin impact than a 2700 K Planckian, given recent melanopsin action
spectra while the lighting levels between the reading chair and the dim
far corner of the living room may differ by more than an order of magnitude.

Ingo
Sepp Ruf
2014-04-14 12:24:07 UTC
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Post by Ingo Thies
In today's lighting market there is essentially no degree of freedom to
the consumer to make any adaption since retail stores in Germany only
offer 2700 or even 2500 K CFL and LEDs. Sometimes you might still get
one with 3000 K, but for higher CCT you need to search the online stores
for something fitting.
Actually, looks like Ingo could simply take a walk, pick up one of nine
currently available 10W, 865 colored, Edison retrofits at Conrad's retail
location there at Bonn:
http://www.conrad.de/ce/en/product/396685
Simple beam geometry, though, and it's spectrum leaves room for improvement,
too:
<Loading Image...>
Post by Ingo Thies
To my knowledge, even light of 5 lux or more can cause sleep problems,
and recent studies presented on "Deutschlandfunk" radio suggests that
even the 0.2-0.3 lux of the full Moon could cause trouble to some
people.
Did not find your or other lux numbers there. The related study expressly
did not involve variably lit rooms:
<http://www.chronobiology.ch/wp-content/uploads/publications/cajochen_2013-06.pdf>
Ingo Thies
2014-04-14 13:22:40 UTC
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Post by Sepp Ruf
Actually, looks like Ingo could simply take a walk, pick up one of nine
currently available 10W, 865 colored, Edison retrofits at Conrad's retail
http://www.conrad.de/ce/en/product/396685
I am actually well equipped with LEDs mostly ordered online; and at
least recently Conrad in Bonn didn't have these available.

However, Conrad has quite few retail stores in Germany, and most other
stores only have 2500-3000 K stuff. Therefore, my statement that the
actual choice of lighting in most homes isn't representative but
strongly affected by the limited offered selection is not yet disproven.

Anyway, the original question, why higher CCT is preferred in other
countries remains unanswered. Given the lack of publications in the www
I guess that there isn't any scientifically reliable answer yet. But the
naive explanation that blueish light makes the hot climate feel "cooler"
does not make sense since the psychical color-warmth does not affect the
physical heat the body needs to cope with.
Post by Sepp Ruf
Did not find your or other lux numbers there. The related study expressly
<http://www.chronobiology.ch/wp-content/uploads/publications/cajochen_2013-06.pdf>
In brief, this paper suggests a kind of inner clock with a 29.5 day
period rather than the actual moonlight being responsible for
full-moon-related sleep disorder.

On the other hand, wake-up lights typically use light levels of no more
than several 100 lux (even of "warm white" light) to wake up people. Or
just turn on the light to wake up anyone sleeping in the room... So
there is indeed a significal effect even far below the intensity needed
to treat SAD. That's what I've said.

Ingo
Sepp Ruf
2014-04-14 18:25:01 UTC
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Post by Ingo Thies
Therefore, my statement that the
actual choice of lighting in most homes isn't representative but
strongly affected by the limited offered selection is not yet disproven.
And this is unlikely to ever get disproven. It also works the other way
around: People got rid of "hot, wasteful" halogens, bought cheap,
low-powered, low-output (usually some cool off-white) LED showerhead lamps
instead. Why? Likely because it's what was being offered at the same
discount retailers where, a few years earlier, they had gotten their
ill-designed halogen luminaires from.
e***@gmail.com
2014-05-19 20:40:20 UTC
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My theory: in hot countries people like to sit in the shade. Which is a cooler CCT.

In cool countries, people like to catch direct sunlight. And that has a somewhat higher CCT. In these countries the sun is also low on the horizon for a longer time every day, leading to very warm sunlight.
Ingo Thies
2014-05-20 08:09:01 UTC
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Post by e***@gmail.com
My theory: in hot countries people like to sit in the shade. Which is a cooler CCT.
The CCT in the shade is actually higher, not lower, since it is mostly
from the blue sky:

http://en.wikipedia.org/wiki/Color_temperature

Blue sky can have up to ~30000 K (and even higher, up to infinity,
according to measurements).

While "cool color" may be interpreted psychologically (i.e. more blue)
the term "cool temperature" is just a sloppy wording for "low temperature"
Post by e***@gmail.com
In cool countries, people like to catch direct sunlight. And that has
a somewhat higher CCT. In these countries the sun is also low on the
No, direct sunlight has a lower CCT, typically up to 5600 K at sea
level. Even lower than the CCT of overcast sky (typically 6000 to 7000
K). It just appears warmer due to its much higher intensity compared to
the shade/overcast sky. A hot bright star with the spectral type O
(e.g. the hottest stars in the Orion Trapezium Cluster), if seen from a
distance where its "disc" appears at the same size as the Sun's "disc",
would have about the same colour as blue sky on Earth, but its light
would be MUCH more intense and hotter. And even at the habitable
distance a brief glance at the star would permanently burn a hole into
your retina while viewing the blue sky (of the Earth, of course) even
for minutes is harmless.

For the same reason, high-CCT LEDs/CFLs may appear "cool": They are far
less intense than the CCT would make us expect. A 5000 K LED with 100
lumens and the apparent lighting intensity of moonlight cannot be
expected to provide the feeling of sunshine.
Post by e***@gmail.com
horizon for a longer time every day, leading to very warm sunlight.
?? Sunlight from the low sun is actually cooler (i.e. less powerful).
Just try: Go out just after sunrise, at noon, and just before sunset on
the same sunny summer day ;-) The colour-psychological "warmth" is
effectively unimportant for sunlight which is dominated by the actual
physical heat. It might be misleading to judge the "warmth" from
photographs since these don't reproduce the actual sweaty effect of noon
sunlight (or the chilling effect of low sunlight, respectively) ;-)

But nevertheless: Exactly this low, weak and reddish sunlight would
rather make people to prefer more bluish artificial (fluorescent/LED)
light in the morning and during the day to compensate for the lack of
sunlight at high latitudes. Only in the evening/night very-low-CCT light
is preferable here to keep the circadian contrast between bright day and
dark night in order to prevent sleep disorder.

But maybe the colour preferences go back to times where only
incandescents were available/widespread, and thus only the night
lighting dominated these preferences. This leads back to the hypothesis
that the colour preferences are simply due to Asian/Mediterranean people
getting used to CCT at times where only "cool" whites were widely
available while northern countries continued to use incans.


Ingo
1***@gmail.com
2014-09-29 10:57:50 UTC
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In Australia (a sunny island continent) the "warm white" seems to outsell
the "cool daylight" bulbs.
The warm white should be renamed as dingy yellow, it is horrible.
Jeff Jonas
2014-11-02 08:59:13 UTC
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Post by 1***@gmail.com
In Australia (a sunny island continent)
the "warm white" seems to outsell the "cool daylight" bulbs.
The warm white should be renamed as dingy yellow, it is horrible.
Interesting color names.
For as long as I remember (from the 60s),
the common tubular fluorescent lamps were
"daylight" (blueish) or "cool white".
Reputable makers (General Electric, Philips)
were very consistent with colors,
so old and new tubes played well together.

A few decades ago, low-end Chinese compact fluorescent lamps
appeared in "dollar shops" in awful colors,
probably too cheap to mix proper phosphors
despite China's monopoly on the "rare earth" metals required.
What was IN the package rarely matched the package.
I wonder if you're suffering that?

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