Which is the best light troughout the day to stay in front of PC?



  • Hello,

    I'm here after listening to a podcast of Dr. Jack Kruse and I have contacted him with the following question:

    Hello,

    I have a question for you because I find it important that we have the information how to use our computer screen throughout the day? We can not al the time go outside in the sun when it is raining or when it is cloudy, freezing, ect...

    I follow you on podcasts but I get no real clear answer how to do this with our computer screens. I have here 3 full spectrum lights and I find this good to sit in it after waking up and when I'm on the pc throughout the day. You have glasses on in front of the screen but is this also necessary around 11h-16h when the sun is bright outside? So why is this a bad thing if we have out screens that emit blue light when outside it is the same? I thought that we need to adjust our screens throughout the day to mimic the light outside. Let say around 08.00h we set the screen to 2700K and around 11h 3500K and around 12-14h we have 5500K and we go down again after 14-16h. I think that this is good thing to do and why not make a program that automatic mimics this throughout the day, so we do not need to do this manual? Here is money to be made with such a program if this is a good idea and that I would ask Jack how he thinks about this and maybe his know someone that can made such a program. It would be better than f.lux or Iris because they do not do this throughout the day automatic. They only do this with day or night but not throughout the day.

    So my question in short is:
    what is now the best Kelvin setting for the computer throughout the day? Or are there several setting to be made from 08.00-16h?

    And his answer was:

    Your question is a problem. The human retina is not built to sustain this type of damage. Therefore when using a computer you should use glasses that block 400-500 nm light. Take breaks and go outside and allow the retina to get a mix of UV-A and IR- A to rebuild the retina you are destroying with the unopposed blue light.


    Does he have a point here that we can restore the eye by getting more in the sun and sitting too long for a screen is not good by the day, even though we use f.lux? And is a program like f-lux not ideal to block those 400-500nm? And how much Kelvin is actually ideal for watching throughout the day before the screen?

    So in short what is the best setting throughout the day?

    Sources:

    https://www.facebook.com/drjackkruse/
    http://www.ledsmagazine.com/articles/print/volume-12/issue-4/features/q-a/questions-abound-about-whether-a-blue-light-hazard-exists.html
    https://www.ncbi.nlm.nih.gov/pubmed/22364266
    https://www.ncbi.nlm.nih.gov/pubmed/22989198
    https://www.ncbi.nlm.nih.gov/pubmed/23898883



  • I think you may be over-thinking this and over-complicating it. The main thing is to make sure you are avoiding blue light for the last ~3 hours or so of your day because blue light interferes with melatonin production. It can suppress it and delay it, and blue light can also interrupt production after it has started. If it gets interrupted, it can take a couple of hours to get going again. So, blue light is "harmful" when you are roughly 3 hours away from going to sleep because you don't want to mess with the timing of your melatonin production. You want it to start when the body wants to start producing it. You don't want to mess with that or else you begin messing with your circadian rhythm. You also don't have to mimic or simulate the same color of daylight throughout the day. There's nothing wrong with leaving f.lux at 6500K all day. The main thing is to use f.lux to help you avoid blue light at night (provided you're already doing that with the type of indoor lighting you're using at night).

    Also, consistent light exposure each day is very important for your circadian rhythm. When you wake up, you should allow yourself to get as much daylight as possible for the first few hours of your day, at minimum. Think about what it would be like if you were living outdoors with no artificial light anywhere for hundreds of miles. What would your light exposure be like every single day? Cloudy or sunny, it doesn't matter. However, there's no good reason to mimic this with a computer monitor because the typical computer monitor is nowhere near bright enough to make enough of a difference (and it has a limited spectrum that it produces). What you need to worry about is doing what you can in the last few hours of your day to avoid blue light - and bright light,, but you should allow full bright blue light exposure as soon as you wake up - and keep allowing it for at least the first half of your day.

    So, f.lux is great for allowing a person to keep a consistent and healthy circadian rhythm because they don't have to worry that their computer will harm that rhythm by using the computer during the last few hours of their day. This is where f.lux comes in. Without f.lux, you wouldn't be able to use your computer at night because it would hurt your melatonin production and thus your circadian rhythm.

    Of course, lots of people have also discovered that, during the day, reducing the amount of blue light that your monitor is producing can help with eyestrain and fatigue due to prolonged computer use. That's why the setting in the beta version of f.lux called "Reduce Eyestrain" reduces the amount of blue light enough to be more comfortable without reducing the monitor's color accuracy too much (it does this in a special way that you cannot simply do by choosing a warmer color temperature).

    So, there are really no rules to this. You don't have to mimic the outdoor color temperature, and you really can't because of how limited a computer monitor is. There's nothing wrong with using 6500K during the day regardless of what it's like outside, just as long as you don't leave it at 6500K during the last few hours of your day. I would recommend the warmest color temperature that you can possibly stand. Of course, it doesn't end there: you should also use blue-free indoor lighting at night, and you might also want to avoid the T.V. unless they make T.V.s now that have a setting that significantly reduces the amount of blue light it emits.

    If you spend the entire day looking at your computer monitor, then maybe just find a color temperature that's more comfortable - or, use the "Reduce Eyestrain" setting. Just go by how you feel. Personally, I have no problem with 6500K all day. I just use a comfortable backlight brightness and that works very well for me because that way my color accuracy is unaffected, and I really enjoy having the best color accuracy possible even though I technically don't need any color accuracy at all. I mean, I'm just a casual user, I'm not doing anything that requires much color at all.

    I think a lot more can be said, but this post is already too long.



  • @TwoCables I'm not the only one has a problem with to much blue light in the day from the screens...

    So why does Dr. Mercola and Jack Kruse make a problem of it if there is no problem at all

    How to Make Digital Screens Healthier

    When it comes to computer screens, Wunsch suggests reducing the correlated color temperature down to 2,700 K — even during the day, not just at night. Many use f.lux to do this....

    With the OLEDs technology, I'm not sure if the color is really stable in every angle you can look at the display," Wunsch says. "But definitely, if you have the screen technology where black is really black, then you have less radiation coming into your eyes and the OLEDs technology is able to provide this.

    So the high contrasts between the black and white, all the black areas in the thin-film-transistor (TFT) screen or the standard screen are not really black. They are also emitting shortwave radiation. The OLED screen only emits where you see light, where there is black on the screen, there is no light. This might be preferable as long as you have no problems with the [viewing] angle.}

    Why I cannot get the link of the source here without getting spam errors! For the source just give in Google: How LED Lighting May Compromise Your Health - Dr. Mercola and then read the article of 23okt 2016.



  • Dr. Mercola likes to over-dramatize things so that he can sell his products. It's pretty much Scare Tactics 101 with him. It's not that he's necessarily wrong about things, but he goes too far and makes his readers think that they have a bunch of health problems to deal with even though they felt just fine before reading his articles. Even when he's not trying to sell one or more of his products, it's like he's one of those tin foil hat people. Y'know what I mean?

    I don't know who this Dr. Jack Kruse is, but I would bet he kinda does the same thing.

    I don't have any problems with leaving f.lux set to 6500K all day, and I literally LIVE at my computer (I spend all day at my computer, every single day). All you have to do is make sure your indoor lighting in your computer room is blended fairly well with the brightness of your monitor and vice versa. Oh, and of course, don't sit too close - like, you know, keep a distance between your monitor and your eyes of like say 2-3 feet or more.

    I don't know if you can see how paranoid these 2 "doctors' are making you be, but it seems to me they have taken away your ability to just relax and enjoy your computer and your life. Try to stop listening to them so much. You're not going to hurt your eyes by simply using a computer. I mean really, look at the rest of the world. Or, look at me. I've been living at my computer for YEARS but I don't have any problems.


  • f.lux team

    You know, there is a lot of basic physics missing from these discussions. A lot of the claims are off by a factor of 1000 or more. So I think you should ask, first, how BRIGHT a light needs to be to do damage.

    Retinal hazards happen because of a dose of energy that's too high, not only because of a particular wavelength.

    First, yes, people do get really upset that the "blue" in a white LED is nearly all at the same wavelength, so when you use a spectrometer it LOOKS like a spike that might poke out your eye. But this is just your imagination - it doesn't actually work like that.

    What actually matters is how much energy is absorbed by the retina, and we can measure energy in "joules" (which is watts times seconds - notice that duration matters!). And we also know that computer displays are just way too dim (hundreds of times dimmer) than light you see outdoors.

    So in hazardous blue light terms: walking to your car (spending a minute outside) gives you a larger dose of blue light than 12 hours of looking at a computer screen.

    But that's for an all-white screen. The same trouble (just more extreme) happens when people try to measure the spectrum of a black pixel. Again, it's 1000 times dimmer than a white screen, and your retina isn't going to notice this. At all.

    Screens with better contrast look better, and colors that match their surroundings also look a lot better. There is a lot of complexity to glare, but more of it is about intensity than it is spectrum for common white lights.


  • f.lux team

    Dr. Wunsch may deserve his own section. He has claimed that IR light has a restorative effect on the retina (and so he claims, this is what makes indoor LEDs bad, because they don't emit IR). I recall he also worries about flicker, which is documented to cause headaches with fluorescent lighting, so this really is a thing to fix.

    But the studies that show any effects like this (on rodents, which are dramatically more sensitive) are done at illuminance levels >100x brighter than indoor lighting.

    Another theme you'll find in the retinal hazard literature is that the most pronounced effects are on albino rodents, which (to oversimplify) will lose their eyesight if they are placed in bright office lighting for a couple days. They are enormously sensitive to light (and nocturnal), and the results do not generalize to humans.

    But again, I will say, before you can talk about spectrum, you MUST make the power similar. Our eyes are so good at hiding the effects of brightness from us - we go from outdoors to indoors (1000:1 in brightness sometimes) and don't really notice the difference. So this makes it very easy to talk about colors and spectra.

    For actual retinal harm, again, you must think about dose (power * time) as the first concern, and spectrum as the second.


  • f.lux team

    To answer the overall topic:

    Because I think "strong" circadian rhythms are very important to health, I think that we should work in places with more light, with brighter screens than we have today. And also, we should spend time before bed in much dimmer spaces.

    Remember that a blue sky can be 50,000K. Outdoors, 5500K is the warm sunlight light you see.

    With a lot of these topics, what we're colliding with is that the way we deliver artificial light (usually in small boxes attached to our ceilings) is not the right shape for the light, so just turning that light up doesn't always work or feel good. It creates new huge glare sources and feels uncomfortable. You don't go outside when the sky is blue and say "this has glare" even though that light is 50x brighter than what you just saw indoors.

    We need to build better ways to bring natural light indoors. I think this should be through a combination of better daylighting, and also with better indoor fixtures.




  • f.lux team

    There are a few false/misunderstood ideas here:

    • "Blue light causes myopia" No, it's quite the opposite, and we know that LACK of exposure to bright light during childhood is linked to myopia.

    • "ICNIRP...": yes, it specifies a hazard spectrum, and also specifies a power + dose that affects the eye. Basically if you are seeing a >10,000 cd/m2 surface for long enough, there may be some calculated retinal hazard by ICNIRP. But your computer display is only 200 cd/m2. Surfaces outdoors are frequently 2000-5000 cd/m2.

    • Humans have not been shown to experience Class 1 retinal harm ("Noell"): these experiments were done in albino rodents, and involve a rod system that continually sheds under moderate intensity light, which our rods do not seem to do.

    • The wavelengths that affect circadian rhythms are different (more green) than those that are implicated in blue light hazard spectra (more high energy blue).

    To demonstrate how the math looks here: in animal models, there is Class II harm (blue light hazard) in doses around 10 J/cm^2. So that is the number you want to exceed based on these standards. (Some of them allow a large safety margin, down to 2.2 J/cm^2).

    The brightest screen we have measured (Apple’s 27" Thunderbolt Display viewed from about 20" away) makes 0.0000125 W/cm2 of “blue light hazard” irradiance. To get from Watts to Joules, you just multiply by seconds, and that gives a number we can compare to the retinal hazard experiments:

    A 1-hour exposure to the very brightest screen we’ve measured is 0.045 J/cm2 at the cornea, a couple orders of magnitude below the threshold for damage.

    And a 12 hour exposure? Only 0.54 J/cm2. So these are really different categories of dose.


  • f.lux team

    Here is a link to the myopia research - this is now in the ophthalmology textbooks, so it's very well regarded research:

    http://www.cnn.com/2011/HEALTH/06/01/myopia.causes/

    Regarding focal comfort, people with presbyopia (those older than 45) will find it easier to focus at close distances with bluer colors - adjusting to a warmer color will make these people need to push the screen another inch or two away.

    It is true that blue light focuses closer, but for most people, it's a difference in intensity with the surroundings that causes eyestrain, not the focal accommodation.

    Again, the blue sky is very very blue, and we shouldn't be afraid of it.



  • You have me thinking differently about my lighting setup TwoCables and herf thanks for sharing, that was informative, even if I don't have a firm grasp of the physics behind it all.

    Do you have any suggestions for people like myself who do not own a spectrophotometer or other technical equipment to loosely gauge whether intensity and contrast between the monitor and indoor lighting are appropriate?

    Say I did buy a spectrometer or something, what then?

    Herf, is that to say we need larger light fixtures?

    I am fantasizing a DIY diffuse lighting system that covers the entire ceiling of a home with a material like soft light setups that photographers use.

    I wonder if rolls could be ordered made of that material.

    More importantly, I have yet to encounter a smart-bulb worth investing in mass quantities to make an array like I am imagining much less screw into the conventional wall/lamp sockets.

    Have you come across any bulbs that you're excited about?



  • @adamlogan said in Which is the best light troughout the day to stay in front of PC?:

    You have me thinking differently about my lighting setup TwoCables and herf thanks for sharing, that was informative, even if I don't have a firm grasp of the physics behind it all.

    Do you have any suggestions for people like myself who do not own a spectrophotometer or other technical equipment to loosely gauge whether intensity and contrast between the monitor and indoor lighting are appropriate?

    Say I did buy a spectrometer or something, what then?

    My suggestion is, don't worry about it because it doesn't really matter. There's no such thing as really having an "appropriate" balance like that. You don't need to use equipment like that (no one else here is doing that, at least that I'm aware of - because it's not needed). Besides, a computer monitor is nowhere near bright enough to matter or worry about in this regard. As long as you're comfortable and you're working on avoiding blue and bright light in the last ~3 hours of your day before you finally get into bed, you're fine. You don't have to get super technical with making sure everything is "perfect" somehow. There aren't any real rules to this. Y'know?

    So, don't worry about it or think about it so much. Try to have a more casual and relaxed approach to all this stuff. F.lux exists to simply enable us to use our computers during the last ~3 hours of our day without being blasted by too much blue light. Of course, even then, you have to consider indoor lighting and the T.V. and other things that still emit too much blue light. Brightness is very important as well though: the brighter a light is, the more "alerting" it is. It's even worse when that light has a decent amount of blue light in it because the brighter a light is, the more intense all of its colors are (which I guess is obvious, but it's always worth mentioning).

    Really though, I would say that we're over-thinking this a little bit too much. I think it can be just as simple as making sure you're doing your best to avoid blue light during the last ~3 hours of your day so that your body can begin producing melatonin and never be interrupted. So avoid very bright light too. You don't have to go any further or deeper than that. Think back to nature, back to basics, etc.

    @adamlogan said in Which is the best light troughout the day to stay in front of PC?:

    Herf, is that to say we need larger light fixtures?

    I am fantasizing a DIY diffuse lighting system that covers the entire ceiling of a home with a material like soft light setups that photographers use.

    I wonder if rolls could be ordered made of that material.

    More importantly, I have yet to encounter a smart-bulb worth investing in mass quantities to make an array like I am imagining much less screw into the conventional wall/lamp sockets.

    Have you come across any bulbs that you're excited about?

    I know this wasn't directed at me, but I just have a comment to make: I'm really not so sure it's worth anyone's time or effort to take things this far.


  • f.lux team

    One way is to buy a cheap lux meter on Amazon, and post the values here for your workspace (with screen off and on), and the room you are in before bed (screen off and on).

    These numbers ignore spectrum, but they make a neat discussion.

    Here, we've lit our office at >500 lux of 5000K LED, and our house can do <5 lux of 1500K before bed. This nighttime setting is maybe extreme for some people, but I think it's actually a reasonable start to the "control" we need to affect circadian timing.


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