I Making LED bulbs safer: Health and LEDs

[renault]

I am thinking about the health aspects of home led lighting and whether it is possible to filter out the shorter wavelength light. I am not sure what manufacturers do in order to produce their 'warm light' bulbs. They claim a lower colour temperature but how are they achieving that?

 

[berkeman]

Welcome to PF.

Are you thinking about eye strain from too much blue from some LED light fixtures? What health effects specifically are you concerned about? Can you provide some links to the reading you've been doing about this? Thanks.

 

[renault]

hi and thanks for your reply. My understanding is that the shorter wavelengths (350-450nm.) destroy melatonin which leads to poor sleep and can result in macular degeneration. The 'soft white' bulbs claim a colour temperature of 1800- 2000 °K. but I don't know if that is even correct - or how it is achieved.

I am thinking that the semiconductor producing the light continues to produce between 350 - 700 nm. so my difficulty is understanding how only the longer wavelengths emanate from the so called 'warm white' bulbs.

I can't believe that the semiconductor is changed, nor can I believe that the wavelength of light it emanates can be changed so what are the manufacturers doing to achieve this yellow light. Using some kind of phosphor I guess - but I don't understand the process.
cheers

 

[sophiecentaur]

so my difficulty is understanding how only the longer wavelengths emanate from the so called 'warm white' bulbs.

Something you need to realise about our perception of colour is that when we see a reddish or bluish colours (such as the sunset or a blue sky) the spectrum that we are seeing is actually broad band and contains all visible wavelengths with just a 'slope' over the spectral band. Blues and reds are seldom removed from any common light source - except for monochromatic sources and suitably driven TV displays.

Some while ago, I bought myself a small (pen-top size) spectroscope and I've been looking at the spectra of many light sources. The light from a good (i.e. convincing) domestic LED has a much more uniform spectrum than the sunlight we see because it's not affected buy the atmospheric absorption notches in the visible range. Same thing goes for a good tungsten filament. otoh, CFLs are totally disgusting and the spectrum looks unbelievably ridiculous.

 

[berkeman]

The light from a good (i.e. convincing) domestic LED has a much more uniform spectrum than the sunlight we see because it's not affected buy the atmospheric absorption notches in the visible range.

Could you post the spectra from a couple of your LED light bulbs in your home, along with their ratings (power, "warmth", etc.)? That would be interesting to see...

 

[renault]

yes indeed that would be interesting to see. I still don't have my question answered though - that is; the so called 'Edison' old style new LED bulbs clearly appear to show a yellowish light - and they claim a colour temperature of 1800°K. So how do you think they are doing this?

 

[sophiecentaur]

Could you post the spectra from a couple of your LED light bulbs in your home, along with their ratings (power, "warmth", etc.)? That would be interesting to see...

The device is very small and works well when you put your eye right next to it - very impressive in fact. But I never go round to fixing it securely enough to take a photo image.
First of all, I thought there were 'imperfections' in the way it shows the spectrum of the Sun (was it the glass in the window?? etc.) but my new lcds (warm, 3500k) show no such stripes / bands so I have to conclude that I'm actually looking through a good instrument.
I guess I should grasp the nettle and clamp my iPhone to it so that I can do a rough measurement of actual levels.
I seriously recommend you guys should all spend £30~ (eBay) and get one. Hours of fun!!

the so called 'Edison' old style new LED bulbs clearly appear to show a yellowish light - and they claim a colour temperature of 1800°K. So how do you think they are doing this?

Afaik, domestic lighting bulbs start with a UV source which passes through a mix of phosphors to produce any spectrum they want. If you're talking about the 'false filament' lamps then

If you look on the Wiki information about leds in general (plus loads of other sites) there is information about basic monochromatic leds and the history of development from the original red ones. There are systems with three colour sources which can be made to 'look' any colour you want but, unless the sources are broad band then the resulting light is not good as an illuminant; a continuous spectrum is needed for that. I'd imagine that those retro lamps are produced to look nice rather than as a good low temperature illuminant.

 

[pinball1970]

Could you post the spectra from a couple of your LED light bulbs in your home, along with their ratings (power, "warmth", etc.)? That would be interesting to see...

From work, this type of light is used in some UK department stores. This is one is 4000K so slightly orange. All the LED SPDs I have seen have this typical blue spike and characteristic shape.

 

[sophiecentaur]

This is one is 4000K so slightly orange.

Interesting. If you were to try to get good matches for two different 'strongly' coloured cyan fabrics (i.e. blues and greens reflected by the dye and a cyan dye for the other fabric) then you could risk seeing a mismatch when you get home or go outside where the illumination is uniform. Time was when people would take coloured clothes outside the shop to see what they would really look like. Those horrible flu tubes were very popular in department stored. Incredible spectra! I believe the M&S women staff used specially chosen makeup to make female customers feel inadequate and needing new clothes and makeup.

That spectrometer is a 'nice thing' to have at home but would cost a bit. I expect - I wonder; is the coloured bit of the display produced by a proper RGB screen or with printed mask with a monochrome display? Perhaps that's my age talking!

 

[f95toli]

yes indeed that would be interesting to see. I still don't have my question answered though - that is; the so called 'Edison' old style new LED bulbs clearly appear to show a yellowish light - and they claim a colour temperature of 1800°K. So how do you think they are doing this?

It is still not entirely clear what you are asking. Old style bulbs and LEDs have very different working principles.
That said, in both cases the light actually emitted will depend both on the "source of light" (the filament or the LEDs used) and the filters/coatings used.
Hence, there are many, many different ways to achieve a desired bulb temperature so I don't think there is one single answer to your question.
Note that there are also LED bulbs with tuneable temperature (from 1800-6500). Not sure how this is achieved, a best guess would be by using a combination of different LEDs

 

[sophiecentaur]

Old style bulbs

We are not talking about hot tungsten filaments. We are talking of the (used to be) fancy filament-look-alikes which have a string of leds with extras- see the link in the post above.

there are many, many different ways to achieve a desired bulb temperature

Not strictly true. The colour temperature achieved with a led device is artificial and a sort of match to a black body source. The low cost eastern manufacturers often think of a number ; a high number for blue-white and a low number for a warm white. In the old days, temperature meant temperature and was fairly easy to reproduce if you could rely on the voltage value.

I don't think there is one single answer to your question.

you are absolutely right. All you can do is use (full price) led bulbs from just one manufacturer throughout a room or house if you want consistency. If you are into Feng shui then you have to use oil lamps.

 

[pinball1970]

I am thinking about the health aspects of home led lighting and whether it is possible to filter out the shorter wavelength light. I am not sure what manufacturers do in order to produce their 'warm light' bulbs. They claim a lower colour temperature but how are they achieving that?

Worth reading this study.

https://www.ncbi.nlm.nih.gov/pmc/ar... exposure (especially,retinal cell damage [3].

In terms of kit some boxes come with Slightly opaque plastic covers to reduce intensity but the SPD I posted was with that filter.
I will post Lux info tomorrow.

Bottom line is that it is not a good idea to look directly into any bright light.

 

[Vanadium 50]

If you want to block UV, the usual material one uses is glass. So if you want your bulb to put out less UV - and this is mostly UV-A and the lowest energy half of that, so health impacts are at their smallest - the easiest and simplest thing to do is make the bulb thicker.

 

[sophiecentaur]

Theere's always the possibility of wearing tinted glasses in the evening. All levels of filtering are available and it could be cheaper than changing all bulbs in the home. It also can help with those loony blue headlamp bubs which everyone else seems to like.
I have some 'Cocoons' over-glasses for night driving and they are just the job.

 

[pinball1970]

If you want to block UV, the usual material one uses is glass. So if you want your bulb to put out less UV - and this is mostly UV-A and the lowest energy half of that, so health impacts are at their smallest - the easiest and simplest thing to do is make the bulb thicker.

Virtually no UV in the commercial LEDs I've looked at. You can see that in the SPD I posted.

 

[renault]

I am finding this thread very interesting. Thank you all for contributing. I think I would like to ask just two questions at this stage: 1) if it is possible to simply block out the lower wavelengths by 'just wear glasses at night' then why don't manufacturers envelop their bulbs with the same glass and stop the problem at source.?
2) If I understand correctly, manufacturers change the ratio of the elements which form the semiconductor in order that it produces light of a certain colour. So they can produce 'white' light. I guess then the question is how narrow a bandwidth of light can they achieve and can that be sufficient enough to eliminate all the lower wavelengths.

 

[renault]

Interesting. If you were to try to get good matches for two different 'strongly' coloured cyan fabrics (i.e. blues and greens reflected by the dye and a cyan dye for the other fabric) then you could risk seeing a mismatch when you get home or go outside where the illumination is uniform. Time was when people would take coloured clothes outside the shop to see what they would really look like. Those horrible flu tubes were very popular in department stored. Incredible spectra! I believe the M&S women staff used specially chosen makeup to make female customers feel inadequate and needing new clothes and makeup.

That spectrometer is a 'nice thing' to have at home but would cost a bit. I expect - I wonder; is the coloured bit of the display produced by a proper RGB screen or with printed mask with a monochrome display? Perhaps that's my age talking!

yes I remember being told that the meat counter in supermarket was illuminated with lower colour temperature bulbs in order to make the meat look more red. It is true - look down the isle of the supermarket

 

[pinball1970]

Interesting. If you were to try to get good matches for two different 'strongly' coloured cyan fabrics (i.e. blues and greens reflected by the dye and a cyan dye for the other fabric) then you could risk seeing a mismatch when you get home or go outside where the illumination is uniform. Time was when people would take coloured clothes outside the shop to see what they would really look like. Those horrible flu tubes were very popular in department stored. Incredible spectra! I believe the M&S women staff used specially chosen makeup to make female customers feel inadequate and needing new clothes and makeup.

That spectrometer is a 'nice thing' to have at home but would cost a bit. I expect - I wonder; is the coloured bit of the display produced by a proper RGB screen or with printed mask with a monochrome display? Perhaps that's my age talking!

This switch to LEDs is a huge energy benefit as we have discussed before. M&S used TL84 not sure if they still do CCT of 4000K.
The thinking was walking around the store you would like to feel like a home atmosphere, so an orange light, rather than a bright blue light like D65 (6500)

Problem with that is the chromophores in the dyes and pigments behave differently in both lights, especially neutral colours where one colourant is not dominant.

Hence ladies taking products to the window to see what the “real” colour is.It is referred to as colour constancy, not to be confused with metamerism which is two samples matching in one light source but looking different in another.

LEDs will pose the same problem, one of which is a lack of UV content (worse than TL84)

That is an issue because anything where you are trying to showcase a bright white, will end up looking a little yellow.

This is because the optical brightening agent used in paper and textile substrates are activated by UV, absorbing that wavelength then throwing out visible light at the blue end.

Remove the UV you remove the effect.

I have never used a commercial UV LED but I think the CIE are adding two one or two to their “standard” illuminant list.

 

[f95toli]

Also, sources of light that DO emit UV that could be dangerous are regulated (at least here in the UK), similar to the rules around lasers.
Not that this will stop people from buying UV diodes from China, but if you want to use a UV source in the workplace there are all sorts of H&S paperwork you need to do first (where I work we have dedicated courses for this).
Hence, as long as you buy from reputable suppliers there shouldn't be any health risks

 

[Vanadium 50]

stop the problem at source.

What problem?

The fact that the UV-A emission is non-zero? That was true with incandescent bulbs. It's true even with no bulb.

IMaybe the amount of UV-A is unsafe. OK, but then you need to tell us what a safe level is and that the amount that is being produced. Without both numbers, it's hard to take a serious look at this statement.

You are always free to put bulbs in ghlass globes. Got a few in my house. Mostly for decorative reasons, but they are there. Why is this a problem for you?

 

[sophiecentaur]

not to be confused with metamerism which is two samples matching in one light source but looking different in another.

Of course. You can make a 'white' illuminant that has massive holes in its spectrum which will match (metameric) a hot filament (black body). Narrow band pigments could appear almost black if they fall in the holes. It's important to distinguish between analysis of colours and synthesis.

the optical brightening agent used in paper and textile substrates

Haha - to add further confusion to the discussion. In the context of regular colourimetry, the illuminant is assumed to be a black body. When it's not we have a different can of worms. I imagine the mqarketing of 'high quality' lighting (as used in surgery and printing) could risk being like the HiFi trade)

 

[pinball1970]

Of course. You can make a 'white' illuminant that has massive holes in its spectrum which will match (metameric) a hot filament (black body). Narrow band pigments could appear almost black if they fall in the holes. It's important to distinguish between analysis of colours and synthesis.

Haha - to add further confusion to the discussion. In the context of regular colourimetry, the illuminant is assumed to be a black body. When it's not we have a different can of worms. I imagine the mqarketing of 'high quality' lighting (as used in surgery and printing) could risk being like the HiFi trade)

Yes we have had a discussion on this too and that's when you demonstrated, reflectance data on a surface is not the same as discussing a black body.
I have learned a little since then but no where near your level.
I'm trying though!

 

[Drakkith]

My understanding is that the shorter wavelengths (350-450nm.) destroy melatonin which leads to poor sleep and can result in macular degeneration.

As far as I am aware, there is no good evidence that blue and violet light has negative effects on people, including sleep disturbances and macular degeneration. There's an immense amount 'information' that gets tossed around when it comes to health, the vast majority of which is nonsense. Combine that with sensationalist news articles and people jumping on every new fad that pops up and you get an environment that highly susceptible to misinformation, fearmongering, and exaggeration.

1) if it is possible to simply block out the lower wavelengths by 'just wear glasses at night' then why don't manufacturers envelop their bulbs with the same glass and stop the problem at source.?

Because then they wouldn't have white lights. They would have orangish lights.

2) If I understand correctly, manufacturers change the ratio of the elements which form the semiconductor in order that it produces light of a certain colour. So they can produce 'white' light. I guess then the question is how narrow a bandwidth of light can they achieve and can that be sufficient enough to eliminate all the lower wavelengths.

You can't eliminate blue light if you want to achieve white light. You're going to need at least some.

 

[renault]

thanks for your reply drakkith. The oft quoted sentiment that 'there is no good evidence' is not one I support. One can find and quote 'evidence' in every field which supports ones own preferred narrative. I prefer to take the cautious approach and for the moment will accept that low frequency light is able to cause harmful effects and if possible, without causing me too much inconvenience, I would like to take steps to avoid this in my home. It is this stance which prompted me to start this thread. Your second two points say that it is not possible to have white light without blue light. Just to be clear (I am learning a lot here !) would that be the same as saying that it is not possible to achieve white light from a source whose intensity is from around 500nm. to 700nm.?
Finally, is there a direct correlation between colour temperature and wavelength. I can't find a graph showing that there is.
cheers

 

[Vanadium 50]

The oft quoted sentiment that 'there is no good evidence' is not one I support

That's your choice, but be aware that one can never prove the health effects are zero. If there were health effects for one person in a trillion, would we ever know? There aren't a trillion people. There have never been a trillion people.

And why near UV-A and/or blue light? Maybe its red light. Maybe it's green light. Maybe its light from incandescents. Maybe it only becomes safe if we chant the Ooga-Chocka introduction to Hooked on A Feeling. Once you detether your beliefs from the data, where does it stop?

 

[Drakkith]

thanks for your reply drakkith. The oft quoted sentiment that 'there is no good evidence' is not one I support. One can find and quote 'evidence' in every field which supports ones own preferred narrative. I prefer to take the cautious approach and for the moment will accept that low frequency light is able to cause harmful effects and if possible, without causing me too much inconvenience, I would like to take steps to avoid this in my home.

You are free to believe whatever you'd like and to take whatever steps you'd like. But if you come here to PF and ask what steps you can take to protect yourself, you have to accept that we can only give you advice that is based on mainstream literature (or at least our understanding of it). Since that literature doesn't appear to clearly support the idea that blue light is harmful, nor that some protective measures like blue-light blocking glasses are even effective, you cannot fault us for saying so.

Note that you can find a correlation between almost any two things, so the fact that some studies find correlations between blue light and health issues isn't surprising. What is much, much more difficult is finding actual causation between the two.

Your second two points say that it is not possible to have white light without blue light. Just to be clear (I am learning a lot here !) would that be the same as saying that it is not possible to achieve white light from a source whose intensity is from around 500nm. to 700nm.?

That's exactly right.

Finally, is there a direct correlation between colour temperature and wavelength. I can't find a graph showing that there is.

No, but there is one between color temperature and color. The reason there isn't one between color temp and wavelength is that, on the whole, many different combinations of wavelengths can generate the same color. This is why the red, green, and blue pixels on your computer of phone screen can generate yellow, orange, and other non RGB colors.

Note that color temperature is based on a black body, which is a hypothetical perfectly emissive object that emits a predictable spectrum at specific temperature. For example, a 6,000 K black body looks white because its spectrum closely matches that of the Sun, which is the light source our eyes evolved to use. A 4,000 K black body looks slightly yellowish, and as we lower the temperature the color of the object becomes more orange, then red, then disappears completely once the temperature is too low to emit enough visible light to even see.

Also note that the descriptions used in describing lights, such as "natural white", "cool white", "daylight white", and the like are nothing more than marketing words and have little to do with the actual color of the light.

If you'd like to see the spectrum emitted by a black body at some temperature, you can use the following link to make your own graphs: https://www.spectralcalc.com/blackbody_calculator/blackbody.php

 

[hutchphd]

Also note that the descriptions used in describing lights, such as "natural white", "cool white", "daylight white", and the like are nothing more than marketing words and have little to do with the actual color of the light.

They are indeed marketing descriptions but they are not without validity. The CIE ( "Commission Internationale de l'éclairage" ) color response curves are attempts made in 1933 and 1964 to characterize a standard human's vision and color response. Within that context, the meaning of color is pretty well defined. All humans may not percieve colors this way but the majority will, and the system provides a useful, but not unique, characterization. So I quibble with disnissing it out of hand......

 

[renault]

Thanks again for your reply - there is much to unpack there which I thank you for and will digest tomorrow. I must however take exception you your saying "You are free to believe whatever you'd like and to take whatever steps you'd like. But if you come here to PF and ask what steps you can take to protect yourself, you have to accept that we can only give you advice that is based on mainstream literature". This sounds like what the government has been telling us about the jab - 'that the science is settled and we must not be allowed to question it'. Perhaps there are people on this forum who might just not accept the consensus promulgated by 'mainstream literature'.

 

[Vanadium 50]

This sounds like what the government has been telling us

Aye, the beauty of conspiracy theories is that the best conspiracies leave no evidence.

 

[Drakkith]

They are indeed marketing descriptions but they are not without validity. The CIE ( "Commission Internationale de l'éclairage" ) color response curves are attempts made in 1933 and 1964 to characterize a standard human's vision and color response. Within that context, the meaning of color is pretty well defined. All humans may not percieve colors this way but the majority will, and the system provides a useful, but not unique, characterization. So I quibble with disnissing it out of hand......

Perhaps I was overly harsh on the descriptions.

This sounds like what the government has been telling us about the jab - 'that the science is settled and we must not be allowed to question it'. Perhaps there are people on this forum who might just not accept the consensus promulgated by 'mainstream literature'.

You have mistaken "there's no good evidence for this" with "everything is fine, stop questioning, you're being stupid". I don't care whether or not you continue to look into a topic. But I also know that health and safety information about any topic is almost always distorted and misunderstood by virtually everyone not professionally experienced with that topic. If I were to follow every piece of advice on every health topic I can find online I'd never eat red meat, never eat sugar, never eat fats, undercook my food, overcook my food, eat raw food, eat zero processed foods, not watch TV or use a computer, take only 'natural' medicine, get acupuncture or use healing crystals or something, not get vaccinated, not use sunscreen, not get an MRI or an X-Ray, drink non-fluorinated water, drink ionized water, not live near power lines, not use wi-fi or cell phones, use blue-light blockers... should I go on?

The only way people can function is:

1. Trust that mainstream science and medicine is generally correct.
or
2. Distrust mainstream science and medicine, but simply pick and choose what health issue they're going to get scared about and change in their lives since you literally cannot keep up with all the issues that crop up.

I choose to do number one and trust that modern medicine is generally correct and even when they are wrong they will tend to correct themselves over time.

 

[hutchphd]

We live the life of royalty, particularly in the USA and western Europe because our founding fathers embraced scientific method as fundamental truth and attempted to build a society on "self-evident truths" rather than superstitious fears. It has worked out pretty well for me so far, and I am apalled by any attempt to revert us to fearmongering. Those who would profit from it, in clerical robes or workaday garb, are far too sanguine in the attempt, and we need to be steadfast in understanding and demanding the level of proof dictated by scientific method. The balance is very tenuous and those who seed the wind will reap the whirlwind for us all.

 

[renault]

Perhaps I was overly harsh on the descriptions.

You have mistaken "there's no good evidence for this" with "everything is fine, stop questioning, you're being stupid". I don't care whether or not you continue to look into a topic. But I also know that health and safety information about any topic is almost always distorted and misunderstood by virtually everyone not professionally experienced with that topic. If I were to follow every piece of advice on every health topic I can find online I'd never eat red meat, never eat sugar, never eat fats, undercook my food, overcook my food, eat raw food, eat zero processed foods, not watch TV or use a computer, take only 'natural' medicine, get acupuncture or use healing crystals or something, not get vaccinated, not use sunscreen, not get an MRI or an X-Ray, drink non-fluorinated water, drink ionized water, not live near power lines, not use wi-fi or cell phones, use blue-light blockers... should I go on?

The only way people can function is:

1. Trust that mainstream science and medicine is generally correct.
or
2. Distrust mainstream science and medicine, but simply pick and choose what health issue they're going to get scared about and change in their lives since you literally cannot keep up with all the issues that crop up.

I choose to do number one and trust that modern medicine is generally correct and even when they are wrong they will tend to correct themselves over time.

in the interest of not boring others, I will simply say that I wish you well with taking your 'number 1' choices, personally I tend to take your number 2 option, being guided by the 'follow the money' principal and generally what I see around me. I will be happy to continue this line of discussion if you want to create another topic if you wish, but now I am gong to bring this thread back on the topic I started.

 

[pinball1970]

I tend to take your number 2 option, being guided by the 'follow the money' principal and generally what I see around me.

Fair enough but that is zero to do with how Science works and this is a scientific forum. I would read the Forum mission statement again.

"Our mission is to provide a place for people (whether students, professional scientists, or others interested in science) to learn and discuss science as it is currently generally understood and practiced by the professional scientific community."

 

[renault]

What problem?

The fact that the UV-A emission is non-zero? That was true with incandescent bulbs. It's true even with no bulb.

IMaybe the amount of UV-A is unsafe. OK, but then you need to tell us what a safe level is and that the amount that is being produced. Without both numbers, it's hard to take a serious look at this statement.

You are always free to put bulbs in ghlass globes. Got a few in my house. Mostly for decorative reasons, but they are there. Why is this a problem for you?

I am interested in your idea of putting bulbs in glass bowls. Just as an example, are you saying that if I put a jam jar over my bulb, the wavelengths of light emanating from the jam jar would change.?
I am also curious how the bulbs with variable colour temperature work. the claim variability between 2800 and 6000°K.

 

[Bystander]

https://www.edmundoptics.com/c/optical-filters/610/

 

[Vanadium 50]

are you saying that if I put a jam jar over my bulb, the wavelengths of light emanating from the jam jar would change.?

I am saying the wavelength distribution would change.

But how do you know that one jam jar is sufficient? Why not two? Why not ten? Why is the bulbe not sufficient? When you decided you were to believe what you want to believe and to heck with science, that's your choice, but part of that choice is that it opens up more questions.

 

[renault]

https://www.edmundoptics.com/c/optical-filters/610/

thanks, this is useful in that now I know that it is possible to produce a notch filter which can eliminate the 'blue spike' outputted from LED bulbs shown to us earlier in this thread (300-400nm.)
So manufacturers could produce bulbs which create this blue light spike at the semiconductor but do not output it from the filter glass enveloping the bulb - and I understand from another contributor to this thread that doing this would mean that we would not have white light but that it would be yellowish. Have I kinda got this right?

 

[f95toli]

Indeed, if your want your source of light to have approximately the same spectrum as daylight you will need quite a bit of blue light included.
Do note that you can't use your eyes to determine colour temperature directly; our eyes adapt based on the light (and surfaces) around us to make things look more or less as they would in daylight. This is why you need to set the colour temperature of your camera* to make the photo look like what you are seeing.

Also, I guess this goes without saying, but there is far, far more UV light in sunlight (with higher energy than in light from LEDs) . If you are worried about the UV in LED light bulbs, you should definitely never spend any time in the sun and at levels we are talking about here probably not even go outside during the day.

*These days most cameras will do an OK job of doing this automatically and the result will usually look similar to what you are perceiving.; but if you want do do it properly you need to calibrate using a grey card (or in the case of a film camera, use the right type of film).

 

[renault]

Indeed, if your want your source of light to have approximately the same spectrum as daylight you will need quite a bit of blue light included.
Do note that you can't use your eyes to determine colour temperature directly; our eyes adapt based on the light (and surfaces) around us to make things look more or less as they would in daylight. This is why you need to set the colour temperature of your camera* to make the photo look like what you are seeing.

Also, I guess this goes without saying, but there is far, far more UV light in sunlight (with higher energy than in light from LEDs) . If you are worried about the UV in LED light bulbs, you should definitely never spend any time in the sun and at levels we are talking about here probably not even go outside during the day.

*These days most cameras will do an OK job of doing this automatically and the result will usually look similar to what you are perceiving.; but if you want do do it properly you need to calibrate using a grey card (or in the case of a film camera, use the right type of film).

thanks, a nice summary. It is not so much that 'I am worried' but generally I take the precautionary principal and if some researchers suggest that current LED's used in the home may cause problems, then I want to consider it. Pinball who posted earlier showed a spectrum from an LED bulb which showed a large spike at around 300-440nm. which he says he has seen in all LED bulbs but it seems that the sun does not produce this spike although it produces 'white' light. I wonder if LED bulbs are unable to produce white light without the 'aid' of this blue spike? - and what the result would be if it were to be filtered out.
I suggest that sunlight is 'pleasant' to us and that the white LED lighting we see in industrial hangars etc leaves one feeling cold and is not a pleasant environment.

 

[hutchphd]

I wonder if LED bulbs are unable to produce white light without the 'aid' of this blue spike?

Google is your friend, unless you prefer to "wonder"....
They sort of mimic fluorescent lights in their optical design. No mercury required, however.

 

[JT Smith]

Pinball who posted earlier showed a spectrum from an LED bulb which showed a large spike at around 300-440nm. which he says he has seen in all LED bulbs but it seems that the sun does not produce this spike although it produces 'white' light.

I'm also mostly uneducated on this subject but what you are saying doesn't seem to be true, at least not in general. Look at these images found with a cursory web search. The first is from LEDs, the second from the sun. The spectrum from sunlight doesn't have a spike but the blue contribution looks to be of similar, if not greater, relative magnitude compared to the orange (at around 600nm).

 

[hutchphd]

They sort of mimic fluorescent lights in their optical design. No mercury required, however.

Is everybody incapable of doing research online?????
The standard "white" LED uses a narrow blue or near-UV LED to excite broadband phosphors which fluoresce to produce the lower energy energy part of the visible spectrum. They produce almost no "far" UV (<200nm): These are energies (>6.2 eV) present in sunlight capable of ionization and causing direct biological harm.
Absent actual good science, I will put my blue blocker glasses on the shelf next to my extensive collection of fashionable aluminum foil hats for indoor apparel.

 

[Drakkith]

The spectrum from sunlight doesn't have a spike but the blue contribution looks to be of similar, if not greater, relative magnitude compared to the orange (at around 600nm).

Indeed. For a 5800 K blackbody, which the Sun closely matches, the spectral radiance is as follows (taken from this website):

350 nm (deep violet): 1.89617e+07 W/m²/sr/µm
400 nm (violet): 2.36154e+07 W/m²/sr/µm
475 nm (blue): 2.6715e+07 W/m²/sr/µm
500 nm (blue-green, Peak emittance): 2.68831e+07 W/m²/sr/µm
550 nm (green): 2.63113e+07 W/m²/sr/µm
600 nm (orange-red): 2.49252e+07 W/m²/sr/µm
650 nm (red): 2.30994e+07 W/m²/sr/µm
700 nm (deep red): 2.1093e+07 W/m²/sr/µm

As you can see, the amount of blue light emitted is quite substantial, very close to the peak radiance. The 450-500 nm band, which is the range we commonly label as blue, would emit more radiation than the red band except that the red band is larger, going from 625-740 nm. The 'spike' in the LED spectrums appears to be necessary for the eye to view them as 'true white'. LED bulbs that are labeled as 'warm white' appear to have a very small or nonexistent spike in the blue region.

I wonder if LED bulbs are unable to produce white light without the 'aid' of this blue spike? - and what the result would be if it were to be filtered out.

They can. Those that lack the blue spike or have a reduced spike are labeled as 'warm white' or something similar and have a yellowish look because of the lack of blue light.

I suggest that sunlight is 'pleasant' to us and that the white LED lighting we see in industrial hangars etc leaves one feeling cold and is not a pleasant environment.

Which is odd, seeing as how a good LED bulb with a 'spike' of blue closely matches the color of the Sun and sunlight (which is white, not yellow or orange as commonly believed). Other than missing the IR light that literally helps warm us, there shouldn't be much difference in the two. Strange, eh?

 

[JT Smith]

Which is odd, seeing as how a good LED bulb with a 'spike' of blue closely matches the color of the Sun and sunlight (which is white, not yellow or orange as commonly believed). Other than missing the IR light that literally helps warm us, there shouldn't be much difference in the two. Strange, eh?

I don't understand how exactly we perceive light but maybe it's due to the missing part of the spectrum compared to the sun? Perhaps the OP should be worried about what's left out with LED lights instead?

We are slowly transitioning to LED lights in our house now that the better ones are close approximations to incandescent and are far better than fluorescent. Our undercounter LED lights are tuneable in color but it's sure not like sunlight; there's no confusing how the two look or make me feel.

 

[Drakkith]

Also remember that this is all subjective. My fiance prefers a 'true white' bulb compared to a 'warm white', as she doesn't like the yellowish lights that many other people do.

 

[JT Smith]

Of course. That's why they sell ones where you can change the color. I'm just saying that I can't set a color that looks natural to me. And significantly, none of the lights "feels" natural. There's a quality to natural light that, to me, just feels better. Maybe my brain is conflating the light with fresh air or open space but I think the light is different in an important way as well.

 

[Motore]

I have warm white and normal white LED bulbs. The normal white feels quite natural. Of course we have LED bulbs now for 5 years and I got used to them. The halogen bulb is just too yellow.
And in now way do LEDs pose any health concern.

 

[f95toli]

Pinball who posted earlier showed a spectrum from an LED bulb which showed a large spike at around 300-440nm. which he says he has seen in all LED bulbs but it seems that the sun does not produce this spike although it produces 'white' light.

And how is that relevant for health effects? A spectra show the distribution of wavelengths, it tells you nothing about intensity. The light outside on a sunny day is way, way more intense than what you get from say a 11W LED, meaning even if the relative amount of blue light is lower than in a LED; the amount of UV you will get exposed to by just being outside is much, much higher.

No one is saying that high energy UV is good for you , it is the main risk factor for skin cancer(use sunscreen and don't use sunbeds). But regular LED bulbs do not produce light at those wavelength, and -as I pointed out above- the intensity of blue light is so low that even if you for reason believe it is a risk factor (which as far as we know it is not); it will be completely negligible compared to just being outside.

 

[renault]

Is everybody incapable of doing research online?????
The standard "white" LED uses a narrow blue or near-UV LED to excite broadband phosphors which fluoresce to produce the lower energy energy part of the visible spectrum. They produce almost no "far" UV (<200nm): These are energies (>6.2 eV) present in sunlight capable of ionization and causing direct biological harm.
Absent actual good science, I will put my blue blocker glasses on the shelf next to my extensive collection of fashionable aluminum foil hats for indoor apparel.

asking questions to learned friendly people on this forum IS part of my research. Nobody is forced to respond.

 

[hutchphd]

Why ask someone to take the trouble to explain something easily understood by a cursory visit to Wikipedia? Seems presumptuous to me.
There actually are interesting questions.