[web2312]

Hello

First of all, sorry for my bad english since I’m Taiwanese.

There are some discussions in chinese monitor forum concerned about the sharp blue spike in the spectrum of W-LED backlights.

Compared to CCFL.

Could WLED-backlit monitors with the blue spike centered at 450mm cause more harm to eyes than CCFL backlighting monitors?

Some users in our forum claimed that LED-backlit monitors can lead to serious eye strain and raise the possibility of cataract eye surgery after long term using.

Therefore, they often suggest CCFL monitors to people who ask for an eye-caring monitor. Is this true?

Thanks for reading!

[PCM2]

Hi Eric,

A good question.

In short, the peak of blue spectral energy for standard W-LED backlights is nothing to be concerned about. It’s worth remembering that whilst the level of blue energy emitted by a standard W-LED backlight is indeed higher (as those spectrum graphs show), monitors filter this light to produce various colours. Even when displaying pure white a W-LED monitor often uses a blue filter bias to help compensate for this spike. When displaying colours other than blue the levels of blue light drop further. As mentioned in the article the filter isn’t 100% efficient and there will still be some spectral differences even after any such filtering. Even so, the difference in HEVL (High Energy Visible Light) energy in the blue region you’re actually exposed to is nothing I’d be concerned about.

And I wouldn’t be concerned about this light anyway. There is some research which I believe was done on post-op cataract patients and others without cataracts in their age group. The studies looked at their lifestyle and sun exposure. There was a relationship between the amount of time spent outside on bright days without any eye protection (sunglasses) and the occurrences of cataracts. This highlights the importance of wearing sunglasses on bright days and days when radiation in general (UV levels) are high during the summer. It seems to have caused some misunderstanding and paranoia to spread in the monitor world, unfortunately. The amount of ‘blue energy’ emitted by even your standard blue-diode W-LED is absolutely miniscule compared to the levels of ‘blue energy’ you would be exposed to simply by going outside (even on a relatively dull day). Blue light is actually one of the signals our body uses to know when it is daytime and to keep us alert during such times (a circadian rhythm cue). It’s why some people suffer from S.A.D (Seasonal Affective Disorder) during bleak winter days and why they can benefit from special lamps that emit very strong blue-spectrum light. This is much stronger than you’d see on any W-LED monitor – and you’d never see a doctor advising patients with S.A.D to stare at their LED-backlit PC monitor for relief.

Having said this I would still advise that users of any monitor use a sensible brightness (200 cd/m² should be more than enough for most situations) and try to take breaks where possible. I would also advise the use of a program such as F.lux to lower the levels of blue light during the night time. None of this is really specifically to avoid any health-scare related occular effects but simply to help reduce eyestrain and aid a restful night’s sleep.

Hope this clears some things up.

[SteveR]

Interesting question, impeccably answered as always by PCM no matter which direction the topic strays.   Do you have a science background Adam?

[PCM2]

Good to see another person who appreciates the topic! I actually initially responded to this topic by email as ‘web2312’ wanted some information to post on Chinese forums. I do have a scientific background (in biological sciences) which is why this sort of thing interests me so much. 🙂

[Retardate]

IMO there is no such light source like display we stare on many hours a day,maybe it’s not that safe for long term use.

The UV leakage and violet light from CCFL also should be compare with blue light of w-led.

Many kind of visual function decrease are not easily detectable and can be accumulate and be irreversible.

Some studies:

Blocking the blue

Eye damage control by reduced blue illumination

Blue light induced apoptosis in rat retina

Age-related maculopathy and the impact of blue light hazard

Blue Light Induces A2E Oxidation in Rat’s Eyes

Blue Light’s Effects on Rhodopsin: Photoreversal of Bleaching in Living Rat Eyes

[PCM2]

There is a lot of sound scientific literature surrounding the subject of HEVL (particularly blue light) and its effect on aging of the eye (in particular macular degeneration). None of those studies, including the ones you listed, actually provide any strong reasons to fear the effect of exposure to light from your average W-LED monitor. It is one thing to be able to demonstrate that irradiating a rat or Rhesus monkey eye (with the former being only loosely comparable to the human eye) with extreme levels of blue light (HEVL) can cause photochemical and photo-receptive damage in the retina. It is quite another to suggest that being exposed to blue light from a monitor could cause any appreciable damage, short or long term, that wouldn’t be caused if that person was simply exposed to the outside world instead.

It is important to remember some of the basics partially covered in my first post. A standard W-LED backlight emits light from a blue diode. The light passes through a yellow (or red mix) scintillating phosphor, reducing some of its energy. It is then filtered by the LCD matrix. The matrix is already configured to place an innate blue filter bias to re-balance the relative strength of the blue channel from the source diode. Further filtering occurs if you are displaying any colour other than white or pure blue.

Under any brightness levels the amount of HEVL emitted from a W-LED backlit monitor is simply nowhere near that you’d be exposed to on a reasonably bright day. Of course it isn’t just W-LED backlights that would emit HEVL. OLED technology and any direct emission backlightless technology also has a blue subpixel component that would emit HEVL. The intensity of this when displaying a mixed image is really not worth worrying about, though. As a point of comparison a monitor’s brightness will typically range from 50-400cd/m² for white. The outside world will typically expose you to HEVL-rich light of between 5,000 cd/m² and 50,000 cd/m² simply through reflection. If the sun is actually beating down onto you then the level of HEVL is increased even more.

Regardless of the diminished intensity of HEVL it is still there, that can’t be disputed. The ‘natural’ alternative to staring at that computer screen throughout the daytime may be to do something outside instead, exposing oneself to a far more intense source of HEVL and of course varying levels of UV. Using a theoretical example of somebody who works outside and then uses various W-LED backlit devices at night – they will be exposing themselves to the highest levels of HEVL. If they were wanting to minimise the effects of this they would be far better off ensuring decent eye protection is worn when outside than cutting off their computer/backlit device use during the night. It’s all about moderation and I would certainly advise sensible brightness and the use of a program like F.lux at night. Again, not specifically to reduce HEVL, but that is certainly achieved as well.

[SteveR]

I agree.  It seems particularly excessive to worry about the health affects of LED monitors.  People forget that before LCD monitors became commonplace we all used to use CRTs which subjected us to ionizing radiation like x-rays from their electron guns!   I’d wager that from a health standpoint, trading ionizing radiation for small amounts of HEVL is a big improvement.

[Retardate]

thanks for your replys guys.

 

I have no science background,just a normal user.

 

I doubt light especially HEVL can effectually reflect through normal outside enviroment like soil trees rocks and get into eyes.When stay outside  there is kind of 5,000 cd/m2 light get into eyes after reflection?really?Cant believe soil or concrate walls can do that.Normally sunlight not get into eyes directly,or retina will burned.

 

I remember a study used few mw blue light (not laser) shine into rhesus eyes 300 sec,after 30min damage has been observed,control group used green light observed nothing.After 48 hours group use green light also observed change,but not obvious like blue light group. The article also have pictures to describe the retina condition.Now I cant find the link.I’ll post link when I find it.

[PCM2]

No problem. The brightness of reflections was just an example. Dark objects such as soil don’t reflect that much light, but lighter objects (especially white) and anything reflective will. And it isn’t so much reflected light that is an issue, it’s the light that enters your eyes directly. It is much more intense than anything a monitor will produce – take a standard glossy monitor or laptop outside on a bright day and you’ll find the screen very difficult to read. Certainly more difficult than if it were inside. In simple terms it is being ‘out competed’ by a much stronger light source, the sun. Even after this energy has been attenuated by the atmosphere and reaches our eye it is several orders of magnitude more intense than a monitor backlight. This is easy to measure with a decent light meter. Press it against the monitor and then take the same light meter outside. The difference is staggering.

Naked blue diodes such as those used to show biochemical effects are much stronger than a monitor backlight, are placed very close to the specimen’s eyes and specifically give off blue light without any sort of filtering. They are good for demonstrating the potential HEVL has to damage, but again are a poor comparison with a monitor’s backlight. There is a particularly interesting study, a collaborative effort between retinal biologists, meteorologists, ophthalmologists and physicists. It is currently a subscription-based read available here. I wouldn’t recommend paying for it, necessarily. It just shows that there are many ‘great minds’ that have studied this particular issue and have really come to the same conclusions. It isn’t something to be concerned about, especially not on something that gives off as little HEVL as a monitor.

[Retardate]

Light-emitting diodes (LED) for domestic lighting: any risks for the eye?

 

11. Conclusions and future directions

Animal models commonly used to evaluate light-induced

degeneration allow mechanisms analysis but are not relevant for

human pathology. Rodents are mostly nocturnal and have rod rich

retina without macula. Limited epidemiologic studies have correlated sun exposure to age-related macular changes, while other

have not. On the other hand, light pollution is increasing exponentially in industrialized countries, with more sophisticated light

sources, with specific spectra and high intensities.

LEDs will most probably become the main light sources. Beside

blue LEDs that are used commonly for decorative purposes, white

LEDs provide retinal exposures to violet, indigo and blue light at

much higher levels than in previous light sources. This is the first

time that the population will be exposed to such substantial blue

light. Whether such retinal exposure will induce increased macular

degeneration? Aggravation of glaucoma neuropathy? Perturbations

of circadian cycles? Nobody can say today, but when analyzing all

the knowledge that has been accumulating on blue-light hazards,

we cannot rule out a yet undiscovered risk for chronic day-long,

life-time exposure since photochemical damages may not induce

any visible changes but cumulatively induce photoreceptors loss.

There is an urgent need for a better evaluation of potential light

toxicity, depending on the different artificial light sources available,

and upon chronic exposure of different populations to define clear

guidelines for domestic light manufacturers.

[PCM2]

Daylight temperature (cool white) domestic lighting is a bit of a grey (or indeed, more of a blue) area. The brightness of your typical LED household light is considerably higher than on a monitor and there is no filtering in place. You don’t generally look directly towards the light, but you are still exposed to HEVL. A large proportion of the French study was actually dedicated to highlighting just how bright some of these LED household lights are. There was also some decent discussion on how intense the sun’s own light can be. The sort of mid-section ‘take home messages’ (particularly ‘Table 9’ and accompanying paragraphs) actually concluded that LED arrays or multiple-die LEDw (your typical household LED lights) which emit warm-white light (2600K-3400K) were no to very low risk (RG/Risk Group 0-1).

The levels of HEVL that you’re exposed to is considerably greater for ‘cool blue’ LEDs, but again we’re talking about light sources which can have a luminance of hundreds of thousands of cd/m². Further research is certainly needed (that’s a common conclusion in academic papers) on these. There was also concern raised that things would get even brighter as LED efficiency improves. There are more recent studies looking at these risk groups and a range of common household light sources as well. Some of these are also, pardon the pun, quite illuminating reads – and draw the extremely important comparison with the much more intense light of the outside world.

Specifically regarding monitor backlights, which give off light that is several orders of magnitude less intense than a household LED light (and is also filtered), things are firmly ‘RG 0’. Improved efficiency will not force brightness up, this will always be something set by the user. It would have been nice if these studies had specifically highlighted this and drawn this comparison, but they are mostly interested in the daemons of the light world. Those cool-blue diodes which sometimes pump out ridiculous luminance. But even then they’re no match for the sun.

[Umbral]

This is their marketing video about blue light on their newest models (EW40 series) :
http://www.youtube.com/watch?v=B8JrVESRcJk#t=31

It may not be only scaremongering. They probably want to emphasize more their monitors functionality compared to other competitors.

[PCM2]

This thread has detailed discussion on this topic. It’s really nothing to worry about and furthermore this ‘Low Blue Light’ (LBL) mode does nothing you couldn’t achieve on most other monitors with manual OSD adjustments. It’s nice to have these modes simply for more relaxing evening viewing, a time where blue light really isn’t your friend. When our EW2740L review is published shortly you’ll see more about the LBL mode.

[cosminignea]

Hi there!
I am wondering if the WLED and RGB LED backlit monitors emits the same amount of blue light.
From what I understand from these graphics it seems to be differences only in green / red light, not on the blue light.

WLED

RGB LED

Thank you!

[PCM2]

Before answering your question, I would like to point out the correct source for this material, which is our article here – https://pcmonitors.info/articles/the-evolution-of-led-backlights/. It is also showing a GB-LED backlight, which is not an RGB-LED backlight.

The Y-axis scale in this case is ‘Relative intensity’, measured in a.u. (arbitrary units). It is important to understand that the graph does not show the total energy or light output for a given wavelength. What the graph is therefore showing is that the energy peak of blue light has a similar relative intensity to green and to a lesser extent red for the GB-LED backlight, but is the sole peak of light energy for the W-LED design. The fact that the end spectrum of the GB-LED backlight contains greater energy in the green and red region than the standard W-LED design does not mean that it contains more or less blue energy.

As explained in the article and hinted at by the name, GB-LED backlights have both a green and blue diode. It is these diodes that control the light output, following interaction with the phosphor coating. The W-LED backlight is outputting predominantly blue light, as it only has blue diodes. The GB-LED design has a more balanced mixture of light output due to the fact it uses green diodes as well. But LCDs filter this light, which complicates matters. The amount of blue light emitted with either backlight design would depend on how the colour channels are set and the brightness of the monitor. Blue light output for a given brightness and colour temperature is going to be largely comparable.

[PCM2]

I’d like to resurface this thread given renewed interest in the topic. This has been partly prompted by this Twitter conversation. A number of monitors have now been certified as ‘Eyesafe’ by TÜV Rheinland. This means they include patented Low Blue Light (LBL) technology to reduce the most energetic wavelengths of HEVL. In implementations I’ve come across, the blue peak is shifted from the typical ~450nm to ~460nm whilst the amplitude of the peak is also reduced. There’s also a subsequent reduction in even more energetic wavelengths such as 435 – 440nm which have the highest ‘harm potential’ for the human visual system. Whilst my overall stance on blue light exposure from monitors remains the same as it always has been in this thread. And I haven’t seen compelling evidence to suggest this is misguided. I still very much welcome what Eyesafe is doing here.

The company did actually say in the linked Twitter conversation that their lawyers advised them not to use the word “harmful” in the context of blue light produced by a monitor. It’s a strong word to use and the balance of evidence suggests it’s a misleading one. I still maintain that you’re exposed to a much lower level of HEVL from monitors than from outside light sources. But I don’t think reducing exposure some of this is a bad thing. There are also some conditions that would increase HEVL exposure from a monitor. If you like to use a high brightness (including spending a lot of time using HDR or simply using SDR at elevated brightness), you like to sit particularly close to the monitor or you’re more interested in spending time with your monitor than sleeping then you’ll increase your HEVL exposure. Having that extra barrier of reduced blue light output for the most energetic wavelengths is very welcome in my view. Even casting long-term aspects aside, for sensitive users the reduction in the most energetic blue light wavelengths can reduce eye fatigue and enhance viewing comfort. As highlighted in that article, though, there are many facets to viewing comfort and this is just one of them.

Another thing worth pointing out if that I strongly advocate reducing exposure to HEVL in the hours leading up to bed. Your body is not naturally supposed to be exposed to blue light at such times. It’s an alertness signal that stimulates the body in ways that are disruptive to sleep, suppressing melatonin. Cutting out the highest energy blue light as Eyesafe technology does is useful here, but it’s best to cut out blue light of all wavelengths. A reduction in monitor brightness can certainly help with this, but I’d also advise using more traditional Low Blue Light (LBL) settings. The Eyesafe certified monitors I’ve used and most I’m aware of include this functionality at the OSD level. So thankfully it seems manufacturers understand that the Eyesafe filtering technology isn’t designed to replace these LBL approaches. But it can certainly complement them as an ‘always on’ solution, useful throughout the day and without impacting colour balance in the way traditional LBL settings do.

[uncia]

That is an interesting concept. I’d be curious to know what high-refresh panels like the VAs out there meet this rating. As I’ve noted before with VA monitors, the far-end of blue edging on violet gives a strange dullness to colors until dialed in. I wonder if this can be improved. I know CCFL that were coated to reduce blue light and produce truer colors as a backlight like with S-PVA models Samsung and Dell came out with were easier on the eyes. Though there is also a definite blue-green tinge that can’t quite be calibrated out. I think that’s just part of being Adobe RGB though.

For cellphone use, I leave mine on blue-light filtering mode most of the time just because the Pixel 4A 5G is far too blue in standard mode. It’s harsh, and the same overly blue note I’ve mentioned with VAs is present here, dulling the colors. The Pixel doesn’t allow you to manually change color.

Viewing comfort of the Asus VG34VQL1B seems fine now that I’ve got colors dialed in. It’s very neutral in color production now, good for creative purposes but perhaps less vibrant than people might wish for. I prefer it after a few weeks of use though. Overly vibrant colors are also hard on the eyes. They’re over-saturated, so it’s not utilizing the color gamut correctly anyway. Accurately mapped 10-bit color to fully utilize this color space would not have the same issues, I don’t believe.

[PCM2]

Yeah, it will be interesting to see Eyesafe expanded. I’m sure there’s broader interest in the technology, but so far the models using this technology have all been based on Innolux AAS (IPS-type) panels and possibly a few BOE IPS-ADS panels mixed in. I don’t see a technical reason it couldn’t be applied to VA panels in the future, but the panel manufacturers will specifically have to work with Eyesafe to have the technology integrated into their displays.

Glad you’re finding the ASUS comfortable following your colour adjustments, though.

[PCM2]

A very interesting issue of the BBC’s “Sliced Bread” program reinforces a lot of the thoughts I’ve shared in this thread. The program originally aired on BBC Radio 4, apologies if this content is region-locked or becomes unavailable some time in the future when people see this post and try to listen to it. You can also listen to it on Apple Podcasts and via Spotify. The section with Professor John O’Hagan (~5:30 onwards) aims to dispel a lot of the unfounded fears surrounding actual long-term damage to the eyes from screen blue light exposure.

The program also delves into its effects on circadian rhythms, where they speak to ‘sleep expert’ Professor Russell Foster (~10:30 onwards). He doesn’t agree that there’s a compelling link between blue light exposure from screens and a significant impact on melatonin levels. Or that the screens would emit sufficient blue light to have such a ‘sleep-disruptive effect’ on melatonin. Though he does concede that the use of Low Blue Light (LBL) ‘filters’ on screens could create a more relaxing viewing experience which would be helpful in itself to aid restful sleep. I certainly find LBL settings beneficial for myself in the evening and have no doubt they improve the quality of my own sleep. I know many others would share these feelings, even if the exact reason for this could be open to question.

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