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> Traditional incandescent bulbs have a ‘colour rendering index’ rating of 100, because they match the hue of objects seen in natural daylight. > Previously re

> Traditional incandescent bulbs have a ‘colour rendering index’ rating of 100, because they match the hue of objects seen in natural daylight. > Previously researchers have warned that the blue light emitted by modern bulbs could be stopping people from getting to sleep at night These two sentences do not go together. Daylight contains LOTS of blue light. 5 seconds of research into CRI says that the first sentence is false. CRI compares a light source to an ideal black body, not necessarily daylight.

flubert 10y ago
>CRI compares a light source to an ideal black body, not necessarily daylight. Isn't the sun a pretty-close-to-ideal black body emitter? Is there something specific you are thinking of that makes daylight deviate significantly from black-body radiation? (Rayleigh scattering in the upper atmosphere?)
- aardvark179 10y ago
  The sun provides a spectrum with a temperature of roughly 6500K, domestic lightbulbs produce something more like 2700K up to 3000K. The biggest difference between incandescent and CF/LED lights is that the spectrum from an incandescent bulb is quite smooth, whereas other lights tend to have a much spikier spectrum meaning you may see some odd colour effects from them and certain materials.
- lutorm 10y ago
  Indeed it is, but that doesn't mean anything illuminated by a blackbody "match the hue of objects seen in natural daylight." CRI has much more to do with the ability to discriminate colors. The absolute hue is a strong function of the color temperature of the illumination, but the eye/brain is also very good at normalizing that away. This is precisely why I don't think people complaining about "nasty cool light" are based in fact. The color of the environment around you will quickly be normalized to be neutral by your brain, and it will be impossible for you to tell whether you are illuminated by a 3000K or 5500K light. You can really only tell color differences accurately.
lutorm 10y ago
I was going to say the same thing. People are confusing "continuous spectrum" with "solar spectrum". Try comparing a "daylight" bulb with a normal incandescent. The color temperature of the sun is ~5500K. The daylight one will look insanely blue, very much like a "cool white" LED or fluorescent. The people that are claiming that incandescent light is "natural" are out to lunch, imho. Maybe it appeals to the cave man inside them, because it's closer to the color of fire?
- cmurf 10y ago
  Yes, the spectral power distribution is smooth for any approximate black body radiator. That low temperature (2700K) incandescent and high temperature (5000K-6500K) daylight have a range of "color temperatures" doesn't negate the smoothness of the distribution. Human chromatic adaptation accounts for this difference automatically very nicely. I guarantee you it's very straightforward to reproduce color mismatches with 5000K "daylight" fluorescents that have CRI 90 and higher, compared to actual daylight. The CRI is just short of complete utter nonsense. It's very useful in specific comparison contexts, but requires qualification. It's almost like having your kid come up with a report card that says B+ and you think, yeah OK not bad kid! But then realist they got A's in everything except they got a D in history. Oops.
- robbrown451 10y ago
  Our eyes can adapt pretty readily to differences in color temperature. What is harder to adapt to (or maybe theoretically impossible) is the non-continuous spectrum. Even if some things look "natural" under such lighting, other things won't, it will shift colors in weird ways. It depends on the pigment etc.
- deleted 10y ago
  [deleted]
LgWoodenBadger 10y ago
Most photographers understand the color temperature differences between incandescent/tungsten light and daylight, and have to account for them by setting their camera's white-balance (manually, or automatically). So it comes as a shock to me that a traditional incandescent bulb's coloring matches that of natural daylight. http://lowel.tiffen.com/edu/color_temperature_and_rendering_demystified.html http://lowel.tiffen.com/edu/color_temperature_and_rendering_...
- agrover 10y ago
  bad reporting.
- tigeba 10y ago
  I think this is a difficult concept for people because our brains do such a good job compensating for mixed lighting. Our built in auto-white balance is too good. One example I use to explain this is the classic Hollywood 'moonlight' trick, which is achieved by using a daylight balanced source like a large HMI, and then using film or a camera that is balanced for tungsten. Looks like daytime to the eye, but on camera it looks like moonlight. There are even special gels just for correcting various light sources CTO (color temp orange) CTB (color temp blue) and minus green (correct gross flo lights). The rest are usually regarded as 'party colors' since they are for non-technical corrections.
- mark-r 10y ago
  You're conflating two concepts, color temperature and CRI. Together they roughly describe the spectrum output; color temperature tells you where the peak output is along the black-body temperature line, and CRI tells you how lumpy the response is. A low CRI can lead to metameric failure[1]. [1] https://en.wikipedia.org/wiki/Metamerism_(color)#Metameric_failure https://en.wikipedia.org/wiki/Metamerism_(color)#Metameric_f...
cmurf 10y ago
CRI is next to b.s. by itself, without further qualification. This is how we get craptastic lights where socks mismatch under a CRI 90+ light but not under daylight. The whole point of CRI is to try to turn a complex evaluation into a simple one, and encourages ignoring the dirty filthy truth about certain kinds of light sources, i.e. its emission lines. If you compare the spectral power distribution of incandescent and daylight (sun light on earth filtered through the atmosphere) they don't look anything alike except that both are very smooth spectra. Whereas LED and fluorescent have very spikey spectra. We tend to not notice these spikes, but sometimes, depending on their location and depending on the materials being viewed under such a light source, they can have a pronounced effect that isn't predicted by CRI. CRI has been a pretty hot potato for some time with a lot of scientists trying to fix it, butting up against a lighting industry that doesn't give a flying crap about accurate color reproduction, they just want a high number CRI so they can sell their shitty lights.
tigeba 10y ago
I think the author has somewhat conflated the concept of CRI and color temperature in the article. An incandescent bulb or a candle has 100 CRI because they are almost by definition close to the ideal. That said a typical incandescent bulb is going to be somewhere in the 2500-3500K color temp. Lots of cheap flo bulbs tend to be both relatively low CRI and have a color temp in the 5000-6000K range which is more like 'daylight without benefits'. They tend to have lots of blue and greens and nothing else. Lots/most LED lights fall in this range as well. My personal opinion is that lighting products should be required to list CRI and color temp, just like nutrition information on food. :)
- me2i81 10y ago
  Yeah, there are fluorescent lights with very high CRIs (for example those in professional light booths) but they cost more because of the phosphor sets.
munificent 10y ago
> Daylight contains LOTS of blue light. Yes, but the sun automatically goes down at night. Most people don't turn off their lights at sunset. I believe what the author is saying that if you have a lot of artificial light after sunset giving off a lot of blue light, it can interfere with your sleep.
- cmurf 10y ago
  There's insufficient evidence the problem results from blue light specifically, rather than the absolute amount of light. I would not be surprised any amount of light that results in mesopic, let alone photopic, adaptation would be a sleep inhibitor. The human visual system is very adaptive, and we're not nocturnal animals, so pretty much anything brighter than moon light pretty much I'd expect would be a potential trigger for "time to be awake".
  - kale 10y ago
    It's the scientific concensus (unless you reject all of the evidence that's out there for the past 15 years). We have multiple receptors in our eyes to do signalling, it's likely that only the S cone cell (low wavelength receptor) suppresses melatonin. This study found no melatonin suppression for higher wavelength light: http://www.ncbi.nlm.nih.gov/pubmed/14962066 http://www.ncbi.nlm.nih.gov/pubmed/14962066 This study also showed the wavelength effect (may be the first big publication on the topic?): http://www.ncbi.nlm.nih.gov/pubmed/11763987 http://www.ncbi.nlm.nih.gov/pubmed/11763987 In addition, not only is it an observed effect, but it can be harnessed. This study showed increase in salivary melatonin by using glasses that filtered lower wavelengths of light: http://www.ncbi.nlm.nih.gov/pubmed/15713707 http://www.ncbi.nlm.nih.gov/pubmed/15713707 The effect is such a strong one that it was discovered despite not being one of the measurements in an unrelated experiment on breast cancer. And throughout antiquity, the only light at night we're exposed to has been that of fire, which is a higher wavelength source.
    - cmurf 10y ago
      Melanopsin retinal ganglion, hmm. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831986/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831986/
mark-r 10y ago
Daylight has a CRI of 100 because the sun is as close to an ideal black body as we're going to get. Perhaps absorption and reflection within the atmosphere lowers it a bit, but I doubt it's significant. As for daylight containing lots of blue, I think that's the point - our bodies have adapted to recognizing blue as the defining characteristic of daylight, and keep us awake for it.
wlesieutre 10y ago
> 5 seconds of research into CRI says that the first sentence is false. CRI compares a light source to an ideal black body, not necessarily daylight. I'll clarify this a bit further: At color temperatures below 5000K (warm/neutral whites), it's compared against an ideal black body. For 5000K and up (cool whites) it's compared against CIE Standard Illuminant D[1], representing a daylight spectrum. Two interesting notes on CRI: 1) This makes CRI discontinuous at 5000K. Two bulbs with very similar color spectrums at 4995K and 5005K can have significantly different CRI scores. 2) CRI of 100 doesn't mean it's "perfect", it means it's the same as a black body emitter (or illuminant D for cool whites). There's some recent research suggesting that people prefer oversaturated reds relative to the black body emitter, but if you put more red in the spectrum it actually lowers your CRI. As far as the two quotes you pulled from the article > Traditional incandescent bulbs have a ‘colour rendering index’ rating of 100, because they match the hue of objects seen in natural daylight. Yep, totally wrong. A tungsten filament bulb is effectively a black body radiator. Being well below 5000K color temperature, it's gauged against the black body spectrum. It's the same spectrum as the reference! Of course it scores well! > Previously researchers have warned that the blue light emitted by modern bulbs could be stopping people from getting to sleep at night This one's a more reasonable statement. Daylight doesn't keep you up at night because there's no daylight at night. The fact that you're running a blue pumped phosphor LED at 11 PM is the potential issue. They have a giant spike of blue in the emission spectrum[2]. Exactly how that affects melatonin levels or your circadian clock is out of my expertise, but it's definitely a real concern that we need to investigate and get a better handle on. [1] https://en.wikipedia.org/wiki/Standard_illuminant#Illuminant_series_D https://en.wikipedia.org/wiki/Standard_illuminant#Illuminant... [2] http://technologyfront.com/journalism/all-pics/true-colors-1.gif http://technologyfront.com/journalism/all-pics/true-colors-1...

flubert 10y ago

>CRI compares a light source to an ideal black body, not necessarily daylight. Isn't the sun a pretty-close-to-ideal black body emitter? Is there something specific you are thinking of that makes daylight deviate significantly from black-body radiation? (Rayleigh scattering in the upper atmosphere?)

aardvark179 10y ago
The sun provides a spectrum with a temperature of roughly 6500K, domestic lightbulbs produce something more like 2700K up to 3000K. The biggest difference between incandescent and CF/LED lights is that the spectrum from an incandescent bulb is quite smooth, whereas other lights tend to have a much spikier spectrum meaning you may see some odd colour effects from them and certain materials.
lutorm 10y ago
Indeed it is, but that doesn't mean anything illuminated by a blackbody "match the hue of objects seen in natural daylight." CRI has much more to do with the ability to discriminate colors. The absolute hue is a strong function of the color temperature of the illumination, but the eye/brain is also very good at normalizing that away. This is precisely why I don't think people complaining about "nasty cool light" are based in fact. The color of the environment around you will quickly be normalized to be neutral by your brain, and it will be impossible for you to tell whether you are illuminated by a 3000K or 5500K light. You can really only tell color differences accurately.

lutorm 10y ago

I was going to say the same thing. People are confusing "continuous spectrum" with "solar spectrum". Try comparing a "daylight" bulb with a normal incandescent. The color temperature of the sun is ~5500K. The daylight one will look insanely blue, very much like a "cool white" LED or fluorescent. The people that are claiming that incandescent light is "natural" are out to lunch, imho. Maybe it appeals to the cave man inside them, because it's closer to the color of fire?

cmurf 10y ago
Yes, the spectral power distribution is smooth for any approximate black body radiator. That low temperature (2700K) incandescent and high temperature (5000K-6500K) daylight have a range of "color temperatures" doesn't negate the smoothness of the distribution. Human chromatic adaptation accounts for this difference automatically very nicely. I guarantee you it's very straightforward to reproduce color mismatches with 5000K "daylight" fluorescents that have CRI 90 and higher, compared to actual daylight. The CRI is just short of complete utter nonsense. It's very useful in specific comparison contexts, but requires qualification. It's almost like having your kid come up with a report card that says B+ and you think, yeah OK not bad kid! But then realist they got A's in everything except they got a D in history. Oops.
robbrown451 10y ago
Our eyes can adapt pretty readily to differences in color temperature. What is harder to adapt to (or maybe theoretically impossible) is the non-continuous spectrum. Even if some things look "natural" under such lighting, other things won't, it will shift colors in weird ways. It depends on the pigment etc.
deleted 10y ago
[deleted]

LgWoodenBadger 10y ago

Most photographers understand the color temperature differences between incandescent/tungsten light and daylight, and have to account for them by setting their camera's white-balance (manually, or automatically). So it comes as a shock to me that a traditional incandescent bulb's coloring matches that of natural daylight. http://lowel.tiffen.com/edu/color_temperature_and_rendering_demystified.html http://lowel.tiffen.com/edu/color_temperature_and_rendering_...

agrover 10y ago
bad reporting.
tigeba 10y ago
I think this is a difficult concept for people because our brains do such a good job compensating for mixed lighting. Our built in auto-white balance is too good. One example I use to explain this is the classic Hollywood 'moonlight' trick, which is achieved by using a daylight balanced source like a large HMI, and then using film or a camera that is balanced for tungsten. Looks like daytime to the eye, but on camera it looks like moonlight. There are even special gels just for correcting various light sources CTO (color temp orange) CTB (color temp blue) and minus green (correct gross flo lights). The rest are usually regarded as 'party colors' since they are for non-technical corrections.
mark-r 10y ago
You're conflating two concepts, color temperature and CRI. Together they roughly describe the spectrum output; color temperature tells you where the peak output is along the black-body temperature line, and CRI tells you how lumpy the response is. A low CRI can lead to metameric failure[1]. [1] https://en.wikipedia.org/wiki/Metamerism_(color)#Metameric_failure https://en.wikipedia.org/wiki/Metamerism_(color)#Metameric_f...

cmurf 10y ago

CRI is next to b.s. by itself, without further qualification. This is how we get craptastic lights where socks mismatch under a CRI 90+ light but not under daylight. The whole point of CRI is to try to turn a complex evaluation into a simple one, and encourages ignoring the dirty filthy truth about certain kinds of light sources, i.e. its emission lines. If you compare the spectral power distribution of incandescent and daylight (sun light on earth filtered through the atmosphere) they don't look anything alike except that both are very smooth spectra. Whereas LED and fluorescent have very spikey spectra. We tend to not notice these spikes, but sometimes, depending on their location and depending on the materials being viewed under such a light source, they can have a pronounced effect that isn't predicted by CRI. CRI has been a pretty hot potato for some time with a lot of scientists trying to fix it, butting up against a lighting industry that doesn't give a flying crap about accurate color reproduction, they just want a high number CRI so they can sell their shitty lights.

tigeba 10y ago

I think the author has somewhat conflated the concept of CRI and color temperature in the article. An incandescent bulb or a candle has 100 CRI because they are almost by definition close to the ideal. That said a typical incandescent bulb is going to be somewhere in the 2500-3500K color temp. Lots of cheap flo bulbs tend to be both relatively low CRI and have a color temp in the 5000-6000K range which is more like 'daylight without benefits'. They tend to have lots of blue and greens and nothing else. Lots/most LED lights fall in this range as well. My personal opinion is that lighting products should be required to list CRI and color temp, just like nutrition information on food. :)

me2i81 10y ago
Yeah, there are fluorescent lights with very high CRIs (for example those in professional light booths) but they cost more because of the phosphor sets.

munificent 10y ago

> Daylight contains LOTS of blue light. Yes, but the sun automatically goes down at night. Most people don't turn off their lights at sunset. I believe what the author is saying that if you have a lot of artificial light after sunset giving off a lot of blue light, it can interfere with your sleep.

cmurf 10y ago
There's insufficient evidence the problem results from blue light specifically, rather than the absolute amount of light. I would not be surprised any amount of light that results in mesopic, let alone photopic, adaptation would be a sleep inhibitor. The human visual system is very adaptive, and we're not nocturnal animals, so pretty much anything brighter than moon light pretty much I'd expect would be a potential trigger for "time to be awake".
- kale 10y ago
  It's the scientific concensus (unless you reject all of the evidence that's out there for the past 15 years). We have multiple receptors in our eyes to do signalling, it's likely that only the S cone cell (low wavelength receptor) suppresses melatonin. This study found no melatonin suppression for higher wavelength light: http://www.ncbi.nlm.nih.gov/pubmed/14962066 http://www.ncbi.nlm.nih.gov/pubmed/14962066 This study also showed the wavelength effect (may be the first big publication on the topic?): http://www.ncbi.nlm.nih.gov/pubmed/11763987 http://www.ncbi.nlm.nih.gov/pubmed/11763987 In addition, not only is it an observed effect, but it can be harnessed. This study showed increase in salivary melatonin by using glasses that filtered lower wavelengths of light: http://www.ncbi.nlm.nih.gov/pubmed/15713707 http://www.ncbi.nlm.nih.gov/pubmed/15713707 The effect is such a strong one that it was discovered despite not being one of the measurements in an unrelated experiment on breast cancer. And throughout antiquity, the only light at night we're exposed to has been that of fire, which is a higher wavelength source.
  - cmurf 10y ago
    Melanopsin retinal ganglion, hmm. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831986/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831986/

mark-r 10y ago

Daylight has a CRI of 100 because the sun is as close to an ideal black body as we're going to get. Perhaps absorption and reflection within the atmosphere lowers it a bit, but I doubt it's significant. As for daylight containing lots of blue, I think that's the point - our bodies have adapted to recognizing blue as the defining characteristic of daylight, and keep us awake for it.

wlesieutre 10y ago

> 5 seconds of research into CRI says that the first sentence is false. CRI compares a light source to an ideal black body, not necessarily daylight. I'll clarify this a bit further: At color temperatures below 5000K (warm/neutral whites), it's compared against an ideal black body. For 5000K and up (cool whites) it's compared against CIE Standard Illuminant D[1], representing a daylight spectrum. Two interesting notes on CRI: 1) This makes CRI discontinuous at 5000K. Two bulbs with very similar color spectrums at 4995K and 5005K can have significantly different CRI scores. 2) CRI of 100 doesn't mean it's "perfect", it means it's the same as a black body emitter (or illuminant D for cool whites). There's some recent research suggesting that people prefer oversaturated reds relative to the black body emitter, but if you put more red in the spectrum it actually lowers your CRI. As far as the two quotes you pulled from the article > Traditional incandescent bulbs have a ‘colour rendering index’ rating of 100, because they match the hue of objects seen in natural daylight. Yep, totally wrong. A tungsten filament bulb is effectively a black body radiator. Being well below 5000K color temperature, it's gauged against the black body spectrum. It's the same spectrum as the reference! Of course it scores well! > Previously researchers have warned that the blue light emitted by modern bulbs could be stopping people from getting to sleep at night This one's a more reasonable statement. Daylight doesn't keep you up at night because there's no daylight at night. The fact that you're running a blue pumped phosphor LED at 11 PM is the potential issue. They have a giant spike of blue in the emission spectrum[2]. Exactly how that affects melatonin levels or your circadian clock is out of my expertise, but it's definitely a real concern that we need to investigate and get a better handle on. [1] https://en.wikipedia.org/wiki/Standard_illuminant#Illuminant_series_D https://en.wikipedia.org/wiki/Standard_illuminant#Illuminant... [2] http://technologyfront.com/journalism/all-pics/true-colors-1.gif http://technologyfront.com/journalism/all-pics/true-colors-1...