# A Study Shows LED May Damage Human Eyes



## slebans (May 17, 2013)

http://www.ledinside.com/news/2013/5/led_damage_human_eyes_20130517


SNIP
Researchers said this is caused by the high levels of radiation in the 'blue band' , and is likely to become a global epidemic in the medium term given that computer, mobiles and TV screens, and even traffic and street lights, have been gradually replaced with LED. Experts are calling for the lights to have built-in filters to cut out the blue glare.


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## slebans (May 17, 2013)

Here's a link to the newspaper story:
http://www.thinkspain.com/news-spain/22749/led-lighting-damages-eyes-says-spanish-investigator

I will find and post a link to the published study if it is in English.


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## arek98 (May 17, 2013)

BS, CFL has more blue than cool white LED, warm LED in 3000K range (common for bulbs and atchitectural lighting) has even less blue.
You can damage an eye with any light if it is strong enough. Blue causes problems with sleeping because it messes with melatonin production but again other light sources have blue band too.


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## jtr1962 (May 17, 2013)

This study makes absolutely no sense. LED backlight computer screens already inherently filter out any blue spikes in order to arrive at the proper ratio of RGB to display colors. Even white won't suffer from the problem of excess blue because 6500K white is a certain ratio of red, green, and blue. As for general lighting, the trend is towards 5000K or less for most types of general lighting. Here the blue spike in LEDs is far less pronounced than it is at higher CCTs. Finally, as arek98 pointed out, CFL already has more blue than LED. Moreover, it has it at shorter wavelengths, along with UV spikes. Same with linear tubes. If people haven't suffered eye problems from fluorescent, it won't be an issue with LEDs. I'm really can't take any article seriously where the lead researcher says stuff like "LED lights are made up of rainbow longitude waves, and it is the blue part which causes the problem." What the heck is a rainbow longitude wave?


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## IMSabbel (May 17, 2013)

The fact that they use "LED rays" immediatly invalidates this story as bullshit (especially if coupled with no publication available).

And the claim would be SO fuzzy that anything would fullfill it. "Prolonged and continuous exposure" alright.


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## JohnR66 (May 17, 2013)

"LED lights are made up of rainbow longitude waves"

Whatever they're smoking. I don't want any.


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## SemiMan (May 17, 2013)

The researcher who published this is respected, and also very political AND has seems to have business relationships with companies that sell yellow filtered glasses and has some patents in this area.

Not use the study was actually done on humans but was tied into some other research that technically did not use LEDs but used a fluorescent source with shorter wavelengths (but not UV).

I could find no published paper and certainly nothing peer reviewed on direct human studies.

Semiman


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## slebans (May 17, 2013)

Here is Dr. Sanchez's company website(this is the English version):
http://www.altaeficaciatecnologia.com/en/areas-de-negocio/prevencion-ceguera-evitable/

I will read through the relevant patents to see if I can find a link to any published papers.


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## Norm (May 17, 2013)

Oh no, I've been looking at the Aussie Blue Sky for sixty years 

I'll just add I always wear UV protection, in the way of UV filtered spectacles.

Norm


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## slebans (May 17, 2013)

Here is a listing of her published research:
http://www.celiasanchezramos.com/index.php?p=23

Going to search for this paper:
Role of metalloproteases in Retinal Degeneration induced by Violet and blue light


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## slebans (May 17, 2013)

slebans said:


> Here is a listing of her published research:
> http://www.celiasanchezramos.com/index.php?p=23
> 
> Going to search for this paper:
> Role of metalloproteases in Retinal Degeneration induced by Violet and blue light



Damn, this paper seems to only be available in a pay per view format. The paper is dated Oct 2012 so perhaps there is a more recent article that is responsible for this mess.
http://onlinelibrary.wiley.com/doi/10.1111/j.1751-1097.2012.01237.x/full


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## AnAppleSnail (May 17, 2013)

In vitro studies are silly without power levels published. There are several non sequitors in the most verbose articles: ” Humans are meant to see with light, not look at it. Consumers (citation needed) are demanding yellow filters to reduce this dangerous radiation in our light.” I'd love to see the power levels. In vitro lets you go to arbitrary power levels (1W/cm sq for 6 hours in a sterilization paper I read recently).


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## SemiMan (May 17, 2013)

slebans said:


> Damn, this paper seems to only be available in a pay per view format. The paper is dated Oct 2012 so perhaps there is a more recent article that is responsible for this mess.
> http://onlinelibrary.wiley.com/doi/10.1111/j.1751-1097.2012.01237.x/full



It is shown that LED radiations decrease 75-99% cellular viability, and increase 66-89% cellular apoptosis. They also increase ROS production and DNA damage. Fluorescence intensity of apoptosis was 3.7% in nonirradiated cells and 88.8%, 86.1%, 83.9% and 65.5% in cells exposed to white, blue, green or red light, respectively. 

.... draw your own conclusions but it seems even red does damage and green a lot which pretty much tells me ANY light does damage.


This paper is 8 months old so I am not sure it is the actual study w.r.t. all the recent news reports.

Semiman


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## SemiMan (May 17, 2013)

http://www.mapfre.com/fundacion/html/revistas/seguridad/n128/docs/Article3.pdf


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## arek98 (May 17, 2013)

Wow, if she is respected then IMO she has an exceptional skills in feeding BS into people with power/money to fund BS researches. Good for her but we don't need to read that.
Staring 12h into any light (or into anything) would damage you eyes or brain, actually I think you would have to have a brain damaged already to do that 
Also it seems she is testing blue, green, and red LEDs. This is not how white LED works. Look for color spectrum graph for white LED. Total BS.


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## slebans (May 17, 2013)

AnAppleSnail said:


> I'd love to see the power levels. In vitro lets you go to arbitrary power levels (1W/cm sq for 6 hours in a sterilization paper I read recently).



Agreed. That's why I was trying to find the published paper. I want to know if she used radiant flux levels higher than we would be exposed to under direct sunlight.


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## SemiMan (May 17, 2013)

slebans said:


> Agreed. That's why I was trying to find the published paper. I want to know if she used radiant flux levels higher than we would be exposed to under direct sunlight.



They are in the link I posted.

Semiman


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## idleprocess (May 18, 2013)

slebans said:


> Damn, this paper seems to only be available in a pay per view format. The paper is dated Oct 2012 so perhaps there is a more recent article that is responsible for this mess.
> http://onlinelibrary.wiley.com/doi/10.1111/j.1751-1097.2012.01237.x/full



There is a small possibility that I could get access to it via one of the dozen-plus library databases at school sometime next week.


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## slebans (May 18, 2013)

SemiMan said:


> They are in the link I posted.
> Semiman




Thanks! I don't know how I missed that.
I still want the original published document as the link you posted is missing a lot of the details of the experiment. Two critical factors that greatly influence the level of damage cause by light are oxygen levels and temperature of the culture medium.
Finally, in vitro does not duplicate the actual environment that the retinal cells are exposed to.

Here is too much info on this subject but the first 25% is easy to read:
http://www.photobiology.info/Rozanowska.html


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## MikeAusC (May 19, 2013)

slebans said:


> and even traffic and street lights, .



Who has BLUE traffic lights in their area ???


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## SemiMan (May 19, 2013)

MikeAusC said:


> Who has BLUE traffic lights in their area ???



Calling into question some of these light sources is just ridiculous given the relative exposure to them versus even a few minutes of being outdoors on a bright day. As has been pointed out, in-vitro is not a great test other than perhaps some relative issues and in the study I linked, even red caused issues and green seem to almost as much as blue. Would be good to see the whole study.

Semiman


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## easilyled (May 22, 2013)

A new study has shown that Aging increases the likelihood of cell-damage and mutations, leading to irreversible changes.


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## inetdog (May 22, 2013)

easilyled said:


> A new study has shown that Aging increases the likelihood of cell-damage and mutations, leading to irreversible changes.



Even more disturbing, visual acuity degrades with frightening rapidity after death.


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## Norm (May 22, 2013)

inetdog said:


> Even more disturbing, visual acuity degrades with frightening rapidity after death.



:lolsign:


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## fyrstormer (May 22, 2013)

slebans said:


> Here is Dr. Sanchez's company website(this is the English version):
> http://www.altaeficaciatecnologia.com/en/areas-de-negocio/prevencion-ceguera-evitable/
> 
> I will read through the relevant patents to see if I can find a link to any published papers.


Looking at this website, it is immediately obvious the good doctor is engaged in producing research to help the sales of eye-protection equipment. You're not going to get welder's blindness from an LED light, at least not unless you stare directly into the emitter at point-blank range for hours.


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## fyrstormer (May 22, 2013)

MikeAusC said:


> Who has BLUE traffic lights in their area ???


When I was a little kid, I used to think the fourth light was a secret blue light for police only. I was very disappointed when I discovered they were green turn-arrows.


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## dc38 (May 22, 2013)

fyrstormer said:


> When I was a little kid, I used to think the fourth light was a secret blue light for police only. I was very disappointed when I discovered they were green turn-arrows.



+1


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## Frijid (Jul 6, 2013)

*Question about LED lightbulbs*

I was reading the warnings today on wikipedia about LED lightbulbs, This is where i became stumped on something

"According to research by Spanish scientists, like other artificial lighting, prolonged direct exposure to LED lights can cause serious damage to retina of the eye, which cannot regenerate. This is caused by high levels of radiation in the blue band"

I'm confused on the "direct exposure to led" part

When it says direct exposure, does that mean installing an LED bulb into the socket, turning it on, and stand a foot away from it and have a staring contest with the thing, 

or does it mean just being around it in general? Like say you install the bulbs, leave them on all day, and stay inside your room or house all day? like just have them on in general for long periods of time?


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## easilyled (Jul 6, 2013)

*Re: Question about LED lightbulbs*



Frijid said:


> I was reading the warnings today on wikipedia about LED lightbulbs, This is where i became stumped on something
> 
> "According to research by Spanish scientists, like other artificial lighting, prolonged direct exposure to LED lights can cause serious damage to retina of the eye, which cannot regenerate. This is caused by high levels of radiation in the blue band"
> 
> ...



Is it not the same argument as staring directly at the sun with its high UV emissions? (which are worse for the retina than blue emissions by the way)

If we intend to destroy our eyesight, we are guaranteed to succeed, but we can choose not to be idiots.


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## LEDninja (Jul 7, 2013)

slebans said:


> Experts are calling for the lights to have built-in filters to cut out the blue glare.


The experts do not know what they are talking about. The devices are RGB. Cut out the B and your screen is RG. The sky would appear black.

It would make more sense to use a lower CCT LED. Makes more sense to make use of the excess blue to produce more light than to waste it by filtering it out.


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## AnAppleSnail (Jul 7, 2013)

LEDninja said:


> The experts do not know what they are talking about. The devices are RGB. Cut out the B and your screen is RG. The sky would appear black.
> 
> It would make more sense to use a lower CCT LED. Makes more sense to make use of the excess blue to produce more light than to waste it by filtering it out.



The 'Experts' are in business selling selective-frequency filters that remove this 'excess' blue.


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## LEDninja (Jul 8, 2013)

I wonder if the researcher only used one type of LED.

This is too blue (probably what the researcher used):






This should be better (XRE Q2-5A neutral white):





High CRI with red LEDs (no wonder people complain about the pink):





Sunlight:





Incandescent bulb:


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## pepperdust (Jul 8, 2013)

cree themselves warn against blue led exposure..

need proof. here


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## idleprocess (Jul 9, 2013)

pepperdust said:


> cree themselves warn against blue led exposure..
> 
> need proof. here



Thankfully, context is provided in the summary:


Cree said:


> The results of this testing (explained below in further detail) show significant health risks from some of Cree’s visible light LED components *when viewed without diffusers or secondary optical devices*. These risks warrant an advisory notice to indicate the potential for eye injury caused by prolonged viewing of blue light from these devices.


Expose yourself to a bright point source _that hurts to view directly_ for a significant duration of time and there's risk to your eyesight - that's somewhat less than surprising.

Looking over the data table, only one product - X-RE Royal Blue - had a risk of injury with momentary exposure. The testing standard IEC 62471-2006 appears to live behind paywalls, so it's difficult to say what type of injury is likely at the 3 risk levels in the Cree document.


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## tobrien (Jul 10, 2013)

there are studies for everything, literally, for every side of it all 

plus, just because someone is a doctor doesn't mean they're not way out in left field and you have to take them seriously.


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## Anders Hoveland (Sep 28, 2013)

*LED lighting may not be good for eyes*

http://www.dailymail.co.uk/health/article-2324325/Do-environmentally-friendly-LED-lights-cause-BLINDNESS.html

This is not the first time a study has suggested that all the blue light in LEDs may not be good for you.

Another compounding factor here is that most LEDs use 455 nm wavelength (which is actually indigo, not blue). This is a shorter wavelength of blue than from other sources, and the photons are more energetic.

This would mostly apply to LED lighting, in spaces that are brightly illuminated where people spend a lot of time in. But it could also possibly apply to computer screens. Probably not the best thing to spend too many hours in front of the computer, regardless of what type of screen you have.
Obviously this would not be an issue for flashlights, no worries.

I found it amusing that the article suggested making the LEDs with built-in filters to “filter out the blue”. Some people obviously do not understand how LEDs work. You can't filter out the blue in LEDs, it is part of the spectrum. Without the blue frequency, the light would no longer be white! Lower correlated color temperature LED lamps have less blue in their spectrum, so if you are concerned about this, it may be best to go with those.
 (But I definitely _do _think CFLs should be built with a filter to filter out the UV radiation they leak out)  


I suppose one potential solution could be to use a regular 455nm chip for stimulating the phosphor, and then another smaller 470nm LED chip to actually provide the blue light in the spectrum. That might help, not sure. Although blue is within the visible range of frequencies, blue photons are rather energetic, they can induce chemical changes in certain instances.

And unless I am missing something, this "blue light hazard" is not unique to LEDs, fluorescent lighting also gives off a short wavelength violet frequency spike. In contrast, not only do incandescent bulbs not radiate a lot of blue, but most of the blue light that they do give off is a longer wavelength, more greenish-blue frequency.


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## Anders Hoveland (Sep 28, 2013)

Studies show blue light causes damage

In an early study conducted by Ham, Ruffolo, Mueller and Guerry, (1980) rhesus monkeys were exposed to high‑intensity blue light at 441nm for a duration of 1000 seconds. Two days later lesions were formed in the retinal pigmented epithelium (RPE.) These lesions consisted of an "inflammatory reaction accompanied with clumping of melanosomes and some macrophage invasion with engulfment of melanosomes which produce hypopigmentation of the RPE" (Ham et al., 1980, p.1110). Since melanin, a common pigment component present in the RPE, strongly absorbs blue light, there is reason to be concerned that the retina is subject to actinic injury from blue light. However, the lens strongly absorbs blue light as well but runs a high risk of possible opacification. In 1992, Chen, a researcher at St. Erik's Eye Hospital in Sweden, sought to explore the basis to explain why blue light reactions cause retinal degeneration. Drawing on the research of E. L. Paulter, Morika and Beenley (1989), who found that a chemical chemical called cytochrome oxidase is a key enzyme in the respiration of the retina in higher mammals, Chen decided to investigate this phenomenon in rats. Cytochrome oxidase is found in the RPE and in the inner segment of the photoreceptors. Paulter's in vitro studies of bovine REP tissue showed that blue‑light exposure destroyed cytochrome oxidase and inhibited cellular respiration. This inhibition was followed by retinal degeneration. Chen then performed a similar experiment upon rats in which he exposed them to 15 minutes of 404nm blue light which was not strong enough to cause thermal damage. He then killed some rats immediately, and one for each of the next three days. Upon examining their retinas, he found the blue light exposure had indeed inhibited the production of cytochrome oxidase. This was evident in his observation of the photoreceptor cells which had been destroyed. He concluded “inhibition of cytochrome oxidase by blue‑light exposure and the consequent suppression of the cellular metabolism is a potential cause of retinal degeneration” (1993, p. 422). 

 In 1980 the group of Sperling, Johnson and Harwerth irradiated the retinas of baboons and rhesus monkeys with blue light. The eye tissues of these primates are very similar to those of humans. In addition to color blindness in the blue‑to‑green range, Sperling et al. found  “extensive damage in the RPE resulting from absorption of energy by the melanin granules. It should be pointed out that the damage seen ... including macrophagic activity, disrupted cells and plaque formation, is characteristic of that seen by Ham et al. (1978), and others in what he calls the photochemical lesion.”

http://www.cclvi.org/contributions/effects1.htm




Norm said:


> Oh no, I've been looking at the Aussie Blue Sky for sixty years


 Pupils dilate/contract under different lighting conditions, letting in more light. It is not good to stare at the sky all day either, most people do not do that. Light is also more intense closer to the equator, different races evolved differently to deal with the glare, Asian eye folds for example. Unless you are an aborigine, not a good idea to be spending all day outside in Australia without sunglasses. Also, people can spend a large amount of time under artificial light sources, often more time than they spend outside.Being outside for too long can make my eyes ache if I amsurrounded by highly reflective surfaces, like on a flat of concrete or out on a lake, although this is probably from the UV, not the blue I suspect.


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## MattPete (Sep 28, 2013)

*Re: LED lighting may not be good for eyes*



Anders Hoveland said:


> http://www.dailymail.co.uk/health/article-2324325/Do-environmentally-friendly-LED-lights-cause-BLINDNESS.html
> 
> This is not the first time a study has suggested that all the blue light in LEDs may not be good for you.....




It's the exact same 'study', this time cited by The Daily Mail (which appears to be of the same quality as The National Enquirer).

The article is full of weasel words. "Some experts have called for the LED lights to have built-in filters..." is meaningless without naming those experts. I bet a case if CREE CR6s that "some experts" refers to Sánchez-Ramos and pretty much no one else.

-Matt

P.S. I am a vision scientist, and this does not pass the smell test.


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## mvyrmnd (Sep 28, 2013)

Yeah, red flags all over this one. A bit like the one recently that said that drinking water heated in a microwave will destroy your DNA.


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## dc38 (Sep 28, 2013)

mvyrmnd said:


> Yeah, red flags all over this one. A bit like the one recently that said that drinking water heated in a microwave will destroy your DNA.



Did you know that looking at ANY profanity deleted LIGHT SOURCE WILL DAMAGE YOUR EYES??? Some people don't think before posting stupid articles...it's like how sound makes us go deaf. Go figure -.-

it's probably much less harmful to walk around blindfolded and ear plugged at this point. What say ye, CPF?


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## Anders Hoveland (Sep 28, 2013)

dc38 said:


> Some people don't think before posting stupid articles...


Some people don't read all the posts in a thread before replying. Light sources with higher ratios of blue, especially shorter wavelength blue can potentially be damaging, as confirmed by several studies. Something to consider if people are going to be under brightly illuminated lighting for long periods of time. If you find the lighting to be a little "harsh", that's probably a sign that it's not the best for you.


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## mvyrmnd (Sep 28, 2013)

Anders Hoveland said:


> Some people don't read all the posts in a thread before replying. Light sources with higher ratios of blue, especially shorter wavelength blue can potentially be damaging, as confirmed by several studies. Something to consider if people are going to be under brightly illuminated lighting for long periods of time. If you find the lighting to be a little "harsh", that's probably a sign that it's not the best for you.



Anything can be 'potentially damaging' if you're exposed to it at high quantities for long periods of time. These 'studies' are written just to drive up fear and drive up/down sales of your/your competitors product. 

They help no one, especially those without any practise in critical thinking.

Show me the double-blind, randomised, controlled, peer-reviewed article on Google Scholar, then I'll start to care.


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## dc38 (Sep 28, 2013)

Anders Hoveland said:


> Some people don't read all the posts in a thread before replying. Light sources with higher ratios of blue, especially shorter wavelength blue can potentially be damaging, as confirmed by several studies. Something to consider if people are going to be under brightly illuminated lighting for long periods of time. If you find the lighting to be a little "harsh", that's probably a sign that it's not the best for you.



Thats it though. I did read all of it, but the way the article portrays led lighting in general is bad. Sunlight is harsh, but it is an essential part of our health. Fire light is harsh, but it is an essential part of our survival in the wilderness. LEDs produce harsh light, but they are an essential development in lighting technology. I'm sure we are all aware that any light going towards the ultraviolet spectrum is especially damaging. Even putting a blue filter on any light is damaging. The point is the same that the others have already posted about, it's not news that higher frequency lighting is bad for our eyeballs. 

@norm, thanks for the filter, because profanity is bad for us too. However, it has become an essential part in the expression of one's frustration. 

Also, might I mention that super intense light is, more than any single property of light, the most damaging of all? Here's an example: *RED* LASERS.
_
*any virtual frustration is directed towards studies by unspecified 'experts' of the obvious*_


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## idleprocess (Sep 28, 2013)

Anders Hoveland said:


> Some people don't read all the posts in a thread before replying. Light sources with higher ratios of blue, especially shorter wavelength blue can potentially be damaging, as confirmed by several studies. Something to consider if people are going to be under brightly illuminated lighting for long periods of time. If you find the lighting to be a little "harsh", that's probably a sign that it's not the best for you.



The posts with screwey text formatting that are wholly copy-pasted from other sources without so much as the courtesy to frame them in quote tags so the extent of your google-bombing becomes readily apparent? Why bother reading them? It _saves time_ to call BS first and see if you can manage anything substantial in the rebuttal.

Also, who hangs out under intense monochromatic blue for any length of time?


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## fyrstormer (Oct 2, 2013)

Besides people in nightclubs? Nobody.


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## AnAppleSnail (Oct 2, 2013)

idleprocess said:


> Also, who hangs out under intense monochromatic blue for any length of time?



People with SAD are sometimes advised to spend a lot of time under high-CCT lights. Some of them are then pushed to simulate this with normal lights + royal blue LEDs.


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## Norm (Oct 2, 2013)

idleprocess said:


> The posts with screwey text formatting that are wholly copy-pasted from other sources without so much as the courtesy to frame them in quote tags so the extent of your google-bombing becomes readily apparent?


Also a violation of rule #5 Articles from other sources are welcome. Links to other websites are welcome. Do NOT post the entire article on CPF! 9 times out of 10, this would be an infringement on copyright. Limit what you post to around 100 words and then post a link to the original source. Always post a link to the original source! 

Noorm


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## idleprocess (Oct 2, 2013)

AnAppleSnail said:


> People with SAD are sometimes advised to spend a lot of time under high-CCT lights. Some of them are then pushed to simulate this with normal lights + royal blue LEDs.


At or anywhere near the intensity levels mentioned in the decades-old study? I find that unlikely.


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## SemiMan (Oct 3, 2013)

AnAppleSnail said:


> People with SAD are sometimes advised to spend a lot of time under high-CCT lights. Some of them are then pushed to simulate this with normal lights + royal blue LEDs.



This is for circadian rhythm and regulating melatonin production. Peak stimulation wavelength should be around 470nm.

Semiman


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## bshanahan14rulz (Oct 3, 2013)

*Re: LED lighting may not be good for eyes*



Anders Hoveland said:


> http://www.dailymail.co.uk/health/article-2324325/Do-environmentally-friendly-LED-lights-cause-BLINDNESS.html
> 
> This is not the first time a study has suggested that all the blue light in LEDs may not be good for you.
> 
> Another compounding factor here is that most LEDs use 355 nm wavelength (which is actually indigo, not blue). This is a shorter wavelength of blue than from other sources, and the photons are more energetic.


355nm is not visible to humans. You may be thinking of ~445-455nm, aka royal blue in some places. This wavelength is present in most white light. 



Anders Hoveland said:


> This would mostly apply to LED lighting, in spaces that are brightly illuminated where people spend a lot of time in. But it could also possibly apply to computer screens. Probably not the best thing to spend too many hours in front of the computer, regardless of what type of screen you have.
> Obviously this would not be an issue for flashlights, no worries.


This I am in agreement with. An anecdote that does seem to agree with you: a coworker of mine spends ~10-12h a day directly in front of a monitor. Lately, he's been wearing computer glasses, which have a slight urine-colored tint to block out some of those shorter visible wavelengths, and he has noticed a distinct decline in headaches.

LED backlights are concerned with getting lots of bright, white light into the lightguide. Cooler end of neutral white gives a decent white while still being very bright, but does contain a bit more blue than the neutral and warm LEDs us tint snobs generally go for. 



Anders Hoveland said:


> I found it amusing that the article suggested making the LEDs with built-in filters to “filter out the blue”. Some people obviously do not understand how LEDs work. You can't filter out the blue in LEDs, it is part of the spectrum. Without the blue frequency, the light would no longer be white! Lower correlated color temperature LED lamps have less blue in their spectrum, so if you are concerned about this, it may be best to go with those.


Hit the nail on the head there! You might take a look at the wavelength graphs posted above, show good example of an older, warm white LED from Cree, compared to a typical cool white LED. You can see the higher counts of oranges and reds compared to the blue spike. Like you said, you can't simply get rid of that blue spike, or you end up with a red-orange LED ;-)



Anders Hoveland said:


> (But I definitely _do _think CFLs should be built with a filter to filter out the UV radiation they leak out)




Most manufacturers assume the glass tube is enough to filter out the shorter UV wavelengths, and that the longer UV waves, being less damaging, aren't as much of a concern. Perhaps someone should invent a frosted glass bulb that fits over CFLs to give them a more lightbulb-y look while also adding a bit more glass between our eyes and the light source. Would make it dimmer, but would also give someone a bit more peace of mind. Didn't you say previously that you are extremely sensitive to all lower wavelengths, even the longer wavelength UV? Might be a fun project for you to look into, a filter that you can retrofit over twisty bulbs.




Anders Hoveland said:


> I suppose one potential solution could be to use a regular 355nm chip for stimulating the phosphor, and then another smaller 370nm LED chip to actually provide the blue light in the spectrum. That might help, not sure. Although blue is within the visible range of frequencies, blue photons are rather energetic, they can induce chemical changes in certain instances.
> 
> And unless I am missing something, this "blue light hazard" is not unique to LEDs, fluorescent lighting also gives off a short wavelength blue frequency spike (it depends on the exact phosphor composition). In contrast, not only do incandescent bulbs not radiate a lot of blue, but most of the blue light that they do give off is a longer wavelength, more greenish-blue frequency.



The sun also gives off a decent amount of shortwave blue relative to other colors too. It is a bit more muted, but much more prominent than a light bulb. Just food for thought. Some folks may be designing to simulate current tech, some may be designing to simulate the color of the sun. We benefit from having such choices when we are making our own lighting devices


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## mvyrmnd (Oct 3, 2013)

"Anecdotal evidence" is a misnomer: anecdotes are not evidence.


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## bshanahan14rulz (Oct 3, 2013)

^dually noted (whatever that means) ;-)


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## SemiMan (Oct 4, 2013)

bshanahan14rulz said:


> ^dually noted (whatever that means) ;-)



Duly


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## bshanahan14rulz (Oct 4, 2013)

SemiMan said:


> Duly



I stand corrective! ;-)


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## mvyrmnd (Oct 4, 2013)

For all intensive purposes, I knew what he meant


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## idleprocess (Oct 4, 2013)

mvyrmnd said:


> For all intensive purposes, I knew what he meant



That was just uncalled for.


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## hank (Nov 14, 2013)

It sounds like a commercially funded paper meant to drive sales, just from reading the comments above. 

There is some real concern about blue light -- anyone who's had an eye exam from an opthalmologist (medical doctor, not an optometrist) has probably noticed they no longer use the very bright blue light after dilating your eyes to look at the retina -- at least where I go (a teaching hospital) for eye exams. Blue photons are are high energy photons compared to anything toward the red end of the visible spectrum -- energetic enough, I recall, to knock the occasional electron off a molecule. That's reason for caution.

'oogle Scholar, limited to 2013: http://scholar.google.com/scholar?as_ylo=2013&q=blue+light+eye+damage
Plenty of research going on about this (limited to 2013 just to reduce the total; the papers go way back if you don't limit the year searched).

My take on this kind of thing is that common sense is scarce enough that doctors do raise concerns -- and that industry generally is very eager to teach the controversy, fund wackos on both sides of any issue, and try to delay any action that affects sales of the products that might turn out to have some risk.

Statistical risk is what public health is all about -- at least when there aren't bodies stacked on the sidewalks, most of us never see anyone who's had any of the statistically risky results. I don't know anyone with lung cancer, right now; I don't know anyone with Thalidomide damage now either -- though I did when I was young. It's been a decade or more since I had a friend who got polio, back when that was fairly common.

Precautions are taken for relatively low risk problems like lung cancer, flipper-limbs, or infantile paralysis once the statistics add up.

Blue light damage seems likely, to me, to be in that same ballpark -- decades from now people will wonder how come nobody realized there were issues to take care of to reduce the small real risks. But at this point, you need a fairly big study, and a competent statistician, to show most of the effects.

Just speculation on my part -- but I do know people with macular degeneration, and I did when I was young know sailors and others who lived with bright sun and glare who did get macular damage, and even then the suspicion was that it was the blue light photons that did the damage, slowly over decades, to their retinas.

Time will tell, on this stuff. We should live so long ...

But it looks to me like the LED manufacturers -- at least Cree, who's come out with a very pure amber phosphor Rebel, among others -- have understood this.
The cheapjack manufacturers can make more money faster selling LEDs driven by the intense blue with a phosphor cover -- we know those leak enough blue light to definitely affect biological systems, of all sorts (look up "turtle safe" lighting, for an example with charismatic megafauna that the newspapers love -- or on the other end, look at how bug lights work and why we use them).;

LEDs driven by green primary emission also solve the problem -- drive the right mix of phosphors and you get perfectly acceptable color rendering, and no risk.

So it goes.

Well, heck, nobody's bothered to read all the stuff I already wrote, so I might as well do a little more. 

Looking back at the original post at the top, I'm going to try to find the paper. If someone else did, I missed seeing it. Pointer welcome.

I have verified that there is, for sure, a city named Madrid, and it's in Spain 

Starting with the newspaper text, I tried 
http://scholar.google.com/scholar?q="Dr+Celia+Sanchez+Ramos"+Madrid+"Complutense+University" -- found nothing.

But -- aha: "Dr" confused the Scholar search.
This finds the scientist and quite a few publications:

http://scholar.google.com/scholar?q="Celia+Sanchez+Ramos" 

I'm guessing the paper written about may be:

http://onlinelibrary.wiley.com/doi/10.1111/j.1751-1097.2012.01237.x/abstract

Effects of Light-emitting Diode Radiations on Human Retinal Pigment Epithelial Cells In Vitro

Eva Chamorro1,*, Cristina Bonnin-Arias1, María Jesús Pérez-Carrasco2,
Javier Muñoz de Luna3, Daniel Vázquez3, Celia Sánchez-Ramos1,2

Photochemistry and Photobiology
Volume 89, Issue 2, pages 468–473, March/April 2013
Article first published online: 9 OCT 2012
DOI: 10.1111/j.1751-1097.2012.01237.x

That looks (to my amateur self) to be a respectable journal; part of the American Society of Photobiology, which I've heard of for years, serious science.
Vision researchers here comment?

Funding for the paper is cited to www.fundacionmapfre.org, which looks respectable: they publish about highway safety, home fire prevention, and much else.
http://www.fundacionmapfre.org/fundacion/es_es/default.jsp


One last thought, for anyone who did manage to read this much --- you know that stuff about yellow filters?
It's real. The lens of the human eye slowly yellows over time as we get older.
That explains why old ladies used to come from beauty parlors with blue-white hair (and some still do).
The optical brighteners that fluoresce in sunlight get added to white-hair cleaning and setting stuff, just like they are added to many laundry products.
And for the same reason -- to brighten the blue end, which aging eyes don't see very well.

(And vice versa -- young children's lenses haven't yellowed at all, so they get a LOT more blue delivered to their retinas than adults -- which is how macular damage may start to accumulate)
(something to remember when giving kids LED lights, or computers, or phones -- they don't see what we see. They see much more blue)

I had a cataract replaced some years back -- the last year _before_ the standard replacement plastic lens began to be made with a far-blue-UV filter material.
Nowadays a cataract replacement lens transmits light about like what gets through a normal aging human lens.

But -- lacking that filter -- my operated eye through the clear plastic lens sees a much bluer world than I see with my normal eye's naturally yellowed, old lens.

And -- yo! I can see into the ultraviolet in the eye that has the cataract-replacement lens.
I can see a couple of spectral bands from fluorescent lights that normal people can't see at all.

That's a bug, not a feature. 
I have to be damn careful about protecting the _operated_ eye in sunlight, as the UV is a real risk to that retina.

But I can walk around at night, using that eye, with a well filtered ultraviolet flashlight that emits almost no light that normal people can see.

It's a stupid party trick. Or a superpower. Not sure which, yet.


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## hank (Nov 19, 2013)

Hm, not just LEDs; lots of papers summarized here: http://physics.fau.edu/observatory/lightpol-BrCa.html


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## idleprocess (Nov 19, 2013)

hank said:


> But it looks to me like the LED manufacturers -- at least Cree, who's come out with a very pure amber phosphor Rebel, among others -- have understood this.
> The cheapjack manufacturers can make more money faster selling LEDs driven by the intense blue with a phosphor cover -- we know those leak enough blue light to definitely affect biological systems, of all sorts (look up "turtle safe" lighting, for an example with charismatic megafauna that the newspapers love -- or on the other end, look at how bug lights work and why we use them).;


"cheapjack" as in _pretty much all LED manufacturers_. Far-more-energetic UV-pumped florescent sources have been around for decades - and we _know_ those leak - and there's no mass outcry over their effects.

As far as I know, there are but a handful of methods to achieve white using LED sources:

*Blue LED + yellow phosphor* : the most common due to the maturity of the concept, its relative economy (cost, energy efficiency), and the steady dividends R&D has yielded (performance, efficiency, color rendition, and cost)
*Discrete RGB die* : the oldest approach, suffers from a lack of economy and some color rendering issues that plague other sources using a handful of discrete color spikes to achieve white (floro, discharge lights). Most often seen in display technology where emitted rather than reflected light is the result.
*UV LED + florescent phosphors* : Works the same way as florescent tubes do, but suffers from rapid package degradation and the ones I heard about some time back had surprising color rendition problems. Available in small quantities a while back, have not heard anything since.
*ZnSe LED* : Of some interest 6+ years ago, I recall these had poor color rendering. Appear to be one or two suppliers of these niche curiosities - or at least some that still offer up datasheets.

While the most common white LED designs emits a good deal of the blue by design, it's desirable to spread that out via the phosphor to achieve good color rendition and even out the spectral distribution.



> LEDs driven by green primary emission also solve the problem -- drive the right mix of phosphors and you get perfectly acceptable color rendering, and no risk.


As far as I know, green is nowhere near as efficient as blue. Also curious how it will achieve lower-wavelength light since every phosphor application I'm aware of downshifts the input frequency into longer wavelengths to achieve a broad spectrum.

I recall seeing a demonstration some time back using a filter of some sort (I want to say it was an orange tint) that achieved a white of sorts, but I suspect that efficiency would be dismal and who knows what the color rendering would be like.


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## hank (Nov 20, 2013)

> green

Here's one example, just from 'oogling for a moment:
http://content.yudu.com/A2gqlk/comsemioct13/resources/36.htm

Here is a reminder of why this is being worked on -- it's to allow nighttime lighting without emission in the 400-500nm band that controls the circadian cycle in people (and animals, and algae -- it's a very old mechanism, showing up all over as people start looking for it).
https://www.google.com/search?q=AMA+health+melatonin+night+light

Why does it matter? 
Well, for any individual, it's probably no big deal. We take 1-in-100 risks comfortably enough.

For populations, where statistics shows up effects you don't always see in yourself or your personal friends, it's a big deal.
And like much else -- it's news. Science is very new in human activities. We're barely learning how to make use of what it can teach us.

So we got these advanced lights -- carbon arcs, HID lamps, and fluorescents (white LEDs are fluorescents).
All emit significant light in the color of the daytime blue sky.

And -- how does biology manage the circadian clock? Easy -- by detecting the color of the daytime sky.
Got that light frequency? Stay awake, stay alert.

No blue light? Countdown timer starts in the brain, and after about 2 hours, melatonin starts to increase, you get sleepy -- and other things happen.
Get a brief flash of white/blue light -- the timer resets because obviously it's still daytime, so your brain has to be kept alert.
Maybe you ducked into a cave briefly -- but it's still daytime, because blue light.

And what happens when we prolong the exposure to the 400-500nm blue band?
Melatonin secretion doesn't ramp up.

What happens as a result?

Turns out -- lots of things depend on having a nighttime circadian cycle with melatonin (and what else?) going up and down regularly.

Lose that and you get irregularities: 
http://www.ij-healthgeographics.com/content/12/1/23

The picture may be enough: http://www.ij-healthgeographics.com/content/12/1/23/figure/F1


A case-referent study: light at night and breast cancer risk in Georgia


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## jtr1962 (Nov 20, 2013)

hank said:


> The picture may be enough: http://www.ij-healthgeographics.com/content/12/1/23/figure/F1


You've heard the old adage correlation doesn't equal causation? What else is generally in areas which are brightly lit at night (i.e. cities and large towns)? Answer is motor vehicles. Lots and lots of motor vehicles. Motor vehicle exhaust is a known potent carcinogen. If we're looking the cause of breast cancers, we need look no further than that. In order to do a controlled study, you would need to compare areas with differing light exposure but equal exposure to other cancer-causing toxins. That's the problem with this entire theory-by definition it's impossible to do controlled studies.


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## rje58 (Nov 20, 2013)

NEWSBREAK! 

A new report has proved BEYOND A SHADOW OF A DOUBT, CONCLUSIVELY what the LEADING CAUSE of DEATH is for humans, pets and in actuality ALL FORMS OF LIFE! It's very shocking to let it sink in and truly realize that this is an indisputable fact. Most people are not aware of this, but once confronted with the facts, can scarcely disagree, even those who still continue to shake their heads and refuse to comprehend the meaning BEHIND those facts.

Yes, a startling new report states beyond all doubt that the leading cause of death is.......life.


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## Anders Hoveland (Dec 5, 2014)

*LED harshness*

Let us, for a moment, move away from whether LED light is _damaging_, and talk about eye strain and glare. 
Now when we are just talking about flashlights, this is not an issue. But when we are lighting a whole room, a room someone will spend a long period of time in, it becomes an issue.

LED light is a little harsh on the eyes, difficult to concentrate on. I do not think it is the _amount_ of blue light necessarily, but rather the specific wavelength. Most of the blue light in an incandescent, for example, is a longer wavelength of blue.

Now fluorescents are not the easiest on the eyes either, but I seem to notice that in terms of glare, LED lighting seems to be about 65% *worse* than fluorescent. This has nothing to do with flicker.

It is not just me who is has noticed this:

"Unfortunately, in September of 2012 my employer replaced the florescent lighting with the newest generation of ECO-friendly lighting most people have still yet to experience, overhead LED bay lighting. There is no description for the pain these lights cause me."*
http://lightsickness.com/


*Now, just as a disclaimer, I have every reason to want to see all the fluorescents converted over to new generation LED, because I have a skin sensitivity to fluorescent. So I am definitely not biased against LED, just bringing up an issue that needs to be discussed.

I am not exactly sure why LED seems to be more glaring. The spectrum of fluorescent contains a moderate 490nm cyan line, so maybe that has something to do with it. Or maybe (?) the violet, despite being a really short wavelength, could be so difficult for the eye to focus on that it becomes more "diffuse" and a little less harsh. 

In terms of color temperature and LED, there are two competing factors here. First, of course, lower color temperature LED has a lower ratio of blue. Second, on the other hand, green-shifted LED phosphor does emit some lesser amount of longer wavelength blue light, the additional presence of this could help counter the perceived harshness. However, typically it is higher color temperature LEDs that have a more green-shifted phosphor composition (there is also high CRI LEDs). I have observed outside LED lighting that had a more greenish tint than the typical purplish-blue tint of most LEDs. These are low CRI, high color temperature, "industrial type" lighting not really designed for indoor use. Obviously they were using a higher ratio of greenish phosphor, presumably to further increase efficiency. But this had the added effect of making the LED light less harsh– observably so– maybe by about 25% less (hard to say exactly, very subjective).

I have a theory that the perceived harshness of light has to do with the ratio of shorter wavelength blue to longer wavelength blue/cyan.

I actually prefer the _color_ of light from higher color temperatures. But just walking into a room and seeing a light source, versus being in that room for several hours, are two different things. 80CRI 2700K LED light has an ugly tinted color, and pretty much sucks the life out of any color in the room, but I would take that over 85CRI 4000K (which pretty much makes colors look okay) because my eyes are going to be squinting.

I have a Cree LS4 fluorescent-replacement tube LED fixture, TrueWhite 92CRI, 3500K. (I got it just for experimentation comparison purposes) While it noticeably adds more color into a room than a fluorescent (especially orange, yellows, and saturated blues ), the aura of light it gives off still has a feeling very reminiscent of fluorescent. Higher CRI does not necessarily mean less harsh.


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## easilyled (Dec 5, 2014)

*Re: LED harshness*

That is an extremely scientific critique ... a link to one person's opinion as well as your own opining and theorizing. Nothing else such as any main-stream research, double-blind studies or trials to offer in evidence.

Well done!


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## idleprocess (Dec 5, 2014)

*Re: LED harshness*



easilyled said:


> That is an extremely scientific critique ... a link to one person's opinion as well as your own opining and theorizing. Nothing else such as any main-stream research, double-blind studies or trials to offer in evidence.
> 
> Well done!



I think it's the 3+ font faces - reminds me of geocities websites circa 1998. Just need some awful background image, colored <hr> bars, and some clipart animated gif's to complete the throwback.


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## SemiMan (Dec 5, 2014)

Scientific my ***. Anders you have said many many times that sunlight does not really bother you so any reference to a blue issue is highly suspect. 

If there is anything of merit perhaps flicker sensitivity and is likely the issue with that person on the plane. Some plane lights have tremendous flicker when dimmed. Many home lights flicker too.

Hook up a DC lab supply with no flicker and then be completely honest in your feedback because right now it sounds like a solution looking for a problem and your credibility based on previous posts is low.


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## Anders Hoveland (Dec 6, 2014)

I am not saying that LED technology necessarily has to be harsh on the eyes (if anything LED technology opens options to engineers to design whatever type of spectrum they want), I am just saying that the _current type_ of LED technology being used is harsh. 

Although I have never actually gotten to experience it, I would imagine that the Xicato Artist series would not be so harsh on the eyes. Because it has much less of a dip in the azure blue and cyan part of the spectrum, it does not need as much of the shorter wavelength blue to get through.


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## Berneck1 (Dec 6, 2014)

Let's face it. Back in the day you could shine an incandescent flashlight at someone and not damage their eyes. Today these lights are exponentially brighter. I'm constantly telling my kids not to flash them into people's eyes. Some of these lights are like looking at the sun! I think I agree it's not LEDs per se, it's the massive amount of light they can produce, concentrated by the reflector. There's no doubt that could be damaging in some way. 


Sent from my iPhone using Candlepowerforums


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## Berneck1 (Dec 6, 2014)

Although, I should add. I do use LED light "bulbs" in my lamps at home. I found the earlier ones too be too harsh, not warm enough. They did bother my eyes a little, not unlike some fluorescent lights. The newer, warmer, lights are exactly the same to my eyes, as the old incandescents. 


Sent from my iPhone using Candlepowerforums


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## Anders Hoveland (Dec 6, 2014)

Berneck1 said:


> Some of these lights are like looking at the sun!


Some of these high power LED emitters are almost like laser diodes! The light is very concentrated, almost in a beam, towards one direction. Even giving it some distance, these emitters still seem incredibly bright when it is directed at you. Yes, I would not be surprised if there was a risk of eye damage from staring directly into the emitters.




Berneck1 said:


> I think I agree it's not LEDs per se, it's the massive amount of light they can produce, concentrated


When discussing LED and glare, I believe there are *two* separate issues. One of them is when a diffusor is not used, the bare exposed LED emitters can cause point-like glare. Especially because the emitted light is so oriented towards one direction.
The second issue, I believe (and this is a contentious topic) has to do with the unique spectrum of LED light. If one looks at a spectral graph, there is a big blue spike, typically centered around 440-460nm. Diffusors do not change the spectrum, obviously. This type of harshness is not something one notices immediately, but takes effect after a few minutes when the entire background is illuminated by LED lighting. A little hard to focus the eyes, at least for me. It is quite possible that some, or even the majority, of people do not perceive any harshness. And what might not be a big deal for outside lighting, could be become much more of an issue for office lighting, where people have to be continually under it for a good part of the day.


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## slebans (Dec 7, 2014)

Berneck1 said:


> Let's face it. Back in the day you could shine an incandescent flashlight at someone and not damage their eyes. Today these lights are exponentially brighter. I'm constantly telling my kids not to flash them into people's eyes. Some of these lights are like looking at the sun! I think I agree it's not LEDs per se, it's the massive amount of light they can produce, concentrated by the reflector. There's no doubt that could be damaging in some way.
> 
> Sent from my iPhone using Candlepowerforums



I would suggest you read:

http://www.candlepowerforums.com/vb...al-safety-material-degradation-etc&highlight=

and

http://www.illuminatedminds.eu/wordpress/the-truth-about-blue-light-and-cancer/


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## martinaee (Dec 12, 2014)

Problem solved.


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## zaidifaran90 (Jan 23, 2015)

*Blue Light Hazardous*

Thread Merge

We want cool white light but it has strong presence (high relative power) of blue light (wavelengths 420~450nm)
As we know blue light hazardous.
Lots of articles can be seen on internet regarding blue lights hazard but no one tells how much blue light is not hazardous (high relative power)
Can anyone tell me how much blue light (relative power) is acceptable or not hazardous?


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## Anders Hoveland (Jan 24, 2015)

*Re: Blue Light Hazardous*

It depends what you mean by "hazardous". Shorter wavelengths of light are more chemically active, and I suspect too much may not be good on the retina. 

Some will tell you that LED light has no more blue than natural daylight. Well, this may be true but it is not the best to have the eyes out in exposed daylight for too long either. Looking at objects in nature illuminated in a natural setting is not the same as looking at indoor objects under artificial lighting. There are several reasons why this is, and too complicated to get into, but just one example is that green plants absorb most of the shorter wavelengths, they are not reflected. Another effect is the ratio of pupil dilation relative the harmful wavelengths in question, pupil dilation being more sensitive to medium wavelengths, so it can really be a matter of ratio, or spectral distribution, rather than actual light intensity.


Longer wavelengths of blue light (485-490nm) may be less hazardous than shorter wavelengths of deep blue light (440-460nm). I strongly suspect this to be the case. It certainly feels softer on my eyes, in any case.


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## night.hoodie (Jan 24, 2015)

*Re: Blue Light Hazardous*

I can not think of anything interesting, insightful, or clever, to post to hide the fact I am merely subsribing to this thread. Ever really watch the color purple? That can make you blue. But if you are true blue, I wouldn't lend any credence to it. Let me know if I blew it.

























What is blue and smells like red paint?
ʇuıɐd ǝnןq​


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## Norm (Jan 24, 2015)

*Re: Blue Light Hazardous*



night.hoodie said:


> I can not think of anything to post to hide the fact I am merely subsribing to this thread.



You don't need to post to a thread to subscribe.

Norm


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## AnAppleSnail (Jan 24, 2015)

I thought "Do colors exist" was a nice primer on color perception. Next would be color spaces and what little we *know* about effects on humans.


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## Anders Hoveland (Jan 24, 2015)

I really do not think we fully realize what the long-term effects of artificial lighting on humans really are. The effects may be much greater on some individuals than others. Humans are more affected by light than most people think. It can lead to chemical changes in the body, either in the retina, the amount of melatonin circulating in the body at certain time periods, or even in some cases in the skin. The amount of UV entering your eyes over your lifetime can certainly affect your cornea in your eyes when you get older, as an example.

There are also likely psychological affects and affects on mental concentration—both conscious and subconscious. Different types of light sources have different spectra, or wavelength distributions in their spectrums. Just comparing the "amount of blue" fails to capture the whole picture I think.


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## night.hoodie (Jan 24, 2015)

Anders Hoveland said:


> I really do not think we fully realize what the long-term effects of artificial lighting on humans really are. The effects may be much greater on some individuals than others. Humans are more affected by light than most people think. It can lead to chemical changes in the body, either in the retina, the amount of melatonin circulating in the body at certain time periods, or even in some cases in the skin. The amount of UV entering your eyes over your lifetime can certainly affect your cornea in your eyes when you get older, as an example.
> 
> There are also likely psychological affects and affects on mental concentration—both conscious and subconscious. Different types of light sources have different spectra, or wavelength distributions in their spectrums. Just comparing the "amount of blue" fails to capture the whole picture I think.



With a handle light that, I can only assume you're closer to the Arctic Circle. What you say is true, concerning psych effects. The Sun regulates our mood. All our energy has our Sun as the penultimate source, all Earth's energy (except nuclear, which comes from supernova, originally, and geothermal, which is from the formation of our Solar System --if missing a source of energy here, please enlighten me).

OT? Light therapy works. Seek that before chemotherapy. Far less damaging to your liver, less disruptive to GI and other systems.


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## alektorophobic (Feb 6, 2015)

I was googling on the the effects of LED lights and thought I would share this research paper. http://ehp.niehs.nih.gov/1307294/


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## Julian Holtz (Feb 6, 2015)

An interesting paper, but nothing new, as blue light damage is known to happen to rats:

http://en.wikipedia.org/wiki/High-energy_visible_light



> *Blue-light hazard* is defined as the potential for a photochemical induced retinal injury resulting from electromagnetic radiation exposure at wavelengths primarily between 400–500 nm. This has not been shown to occur in humans, only inconclusively in some rodent, primate and in vitro studies.



As I read it, humans are not affected. this makes sense to me. Look at the spectrum of an LED:

http://www.advancedaquarist.com/2012/10/aafeature_album/image041.jpg

And sunlight:

http://heatisland.lbl.gov/sites/all/files/imagecache/image_lightbox/Solar Energy Spectrum.jpg

The 450nm range is equally powerful in both.

If LED light was dangerous, how did humans manage it to live for millions of years under the sun? Africans and australian natives hunted all day in the glaring sun, and europeans were farming and herding cattle all day.

Rats on the other had are primarily seen at night, and apes hang out in shadowy trees all the time. Makes sense to me that eyes adapt to the environment they are used in.


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## idleprocess (Feb 6, 2015)

I've looked at some of the conditions in the study and I too had some reservations about it. Rats are largely nocturnal creatures that shun prolonged exposure to sunlight, yet the study subjected them to 14 days of darkness, then subject to 28 days of light for 12 hours a day in small transparent enclosures with the light source a mere 20cm (~8") away. The CFL's and LED's were also unusually cold - (6500K) which would greatly concentrate the blue light - and the LED's were also custom-manufactured for the experiment from a producer I've never heard of.

The Discussion section of the article makes some effort to translate this to risks for humans and also admits that the study's results mostly suggest the need for more testing in order to make solid recommendations on the effects artificial lighting with heavy concentrations of blue light.


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## Anders Hoveland (Feb 7, 2015)

Julian Holtz said:


> If LED light was dangerous, how did humans manage it to live for millions of years under the sun? Africans and australian natives hunted all day in the glaring sun, and europeans were farming and herding cattle all day.


And yet an LED fixture illuminating a room still feels different on my eyes than sunlight through a window. Obviously we are missing something here.

I think we can agree that, just in terms of a direct comparison, sunlight has more of the short wavelengths than LED light, and shorter wavelengths are _typically_ the ones that are more damaging. Based on this reasoning, one would be inclined to think LED is no more damaging than natural sunlight illumination, but this could be ignoring more complex effects. The spectral output from LED may not be "dangerous", but it could be _problematic_, in other ways.

The 3500K LED fixture I have just feels harsh and a little uncomfortable on my eyes, even more so (and in a slightly different way) than fluorescent lighting. There is no discernible flicker, that is not the cause. It just feels a little difficult to focus and my eyes feel a little tired and strained after a few minutes. It's not terrible, but it is noticeable to me.

If you look at a spectral graph, sunlight has a substantially higher ratio of longer blue wavelengths to shorter blue wavelengths than LED, and I strongly believe this has something to do with it. 

The reason for this ratio in the spectrum of sunlight is Rayleigh scattering through the atmosphere, since scattering is dependent on the _fourth_ power of the specific wavelength. So for example, 440nm light would be scattered 53.8% more than 490nm light.




Julian Holtz said:


> Africans and australian natives hunted all day in the glaring sun, and europeans were farming and herding cattle all day.


It's really a separate topic, but there may well be some racial differences here. Not to get too controversial, but it is beyond dispute that some races have different adaptations for sun protection (Africans have higher melanin content in their skin and iris, Asians have increased keratin, and eye folds, etc.).


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## slebans (Feb 8, 2015)

idleprocess said:


> I've looked at some of the conditions in the study and I too had some reservations about it.



I certainly cannot comment on the actual testing and results - way above my pay grade. But the material and methods section, specifically in reference to the lighting components, is missing the necessary information that would be required to duplicate the experiment.

First of all, I am really glad that I am not a Sprague Dawley rat. When I went searching for the animal's physical characteristics I came across more than I ever wanted to know about the "testing" these animals are subject to. I cannot get the lumbar torsion device out of my head!

In honor of the rats sacrificed for this experiment - I thought I might make fun of the research scientists while detailing the issues as I see them.

Two scientists in a meeting.
(names withheld to protect the innocent)
Sci1: The boss wants a funding proposal to show that LED lights in normal home or work environments can cause damage to retinal tissue.
Sci2: But both Europe and USA governments have issued reports stating that LED lights under their intended usage do not cause photobiological damage.
Sci1: Isn't your contract up for renewal next year?
Sci2:Hmmm...I guess we could test using the bulbs that are most popular in Asia. A CCT of 5000K would yield a larger component of blue light than the 2700K variant more popular in Europe and the USA. 
Sci1: Now you're thinking - let's finish this and go see the boss.

10 minutes later:

Boss: Boys, you've got the right idea but I want you to push the envelope a bit.
Sci1: You're the boss!
Boss: Increase the lux by 50%.
Sci2: But the worldwide standard for photobiological testing of this nature is 500 lux!
Boss: LED bulbs are so efficient that people are over lighting their homes and offices. Let's move on.

Boss: Get some 6500K bulbs to replace those 5000K units.
Sci2: But very few people would use higher than 5000K in their homes!
Boss: Are 6500K bulbs available?
Sci1: Absolutely, Boss. Consider it done.
Sci2: (sad face)
Boss: Look Sci2, If it will make you feel any better, add in a 3000K CFL to the testing.
Sci1: Great! How about adding a 3000K LED bulb as well?
Boss: Sorry - too many light sources. Next.

Boss: I want you to add a Royal Blue LED source.
Sci2: But you just said we can't add any more light sources!
Sci1: (elbows Sci2) No problem, Boss. I'll look after it myself.
Sci2: But no company would produce a Royal Blue LED only light fixture!
Boss: (stern look towards Sci2) Do the majority of LED light bulbs employ a phosphor coating over a Royal Blue LED?
Sci2: (pause) Yes.
Boss: Does the phosphor degrade over time - allowing a larger component of blue light to pass through?
Sci2: Yes, but the degradation is minimal before the L70 duration is reached - that's a minimum of 50 thousand hours!
Boss: But it could happen...
Sci2: But..but...for a Royal Blue LED to reach 750 Lux would require more than 7 times the output compared to the other light sources. That's not a fair comparison!
Boss: Life's not fair - just ask the rats you will be using for this experiment.
Sci1: Hahahah - you're so funny, Boss!

Boss: Finally, I want you to use transparent rat cages built from polycarbonate.
Sci2: Why polycarbonate?
Sci1: Sorry, Boss. He's still young. 
Sci1: (turns to Sci2) Polycarbonate blocks light below 400nm. We don't want any unwanted light polluting the experiment.
Sci2: But that's not fair! CFLs do produce light below 400nm. We should include...
Boss: (glares at Sci2) It's not enough light to worry about.

Boss: Ok. Boys. We're done here. I'll let you know when I get the funding approved.
Sci1: Great meeting, Boss. The changes you made will definitely help the experiment. We'll let you get back to work.
Sci2: But...but...but...
Sci1: (drags Sci2 from the room)


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## hank (Jun 22, 2015)

Google Scholar is often helpful, you can look this sort of thing up and find thorough review articles.

Here, for example: http://www.photobiology.info/Rozanowska.html


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