Settings below 2700K during the day



  • Is there a reason behind the limit of 2700K during the day? I'd like to have a consistent setting below that for the whole day, not just bedtime. Is that possible?



  • @Marlon-Thomson Reluctantly yes. You can choose "expanded daytime options" (that's not a direct quote, just my guess at what it says) to go below the already SUPER low setting of 2700K in the daytime.

    So, is it that the white color of your screen is hurting your eyes? Or could it be placebo that you just like the orange color? Sorry, but this gets asked a LOT and I don't mind answering it, it's just that so many people now use f.lux like this, and I just can't believe that so many people need to do this for their eyes to be comfortable. There are some legit users who have stated why they need this, due to very very sensitive eyes and that type of thing, but this is actually starting to get a bit crazy with about 20 or so people asking to do this.

    Do you have windows in the room that you use your screen; because that would help a lot with your eyes adjusting to the screen. Also how often do you see bright outdoor light?



  • Hey!
    Thanks so much! I totally missed that option since i expected it to make the day time longer or something^^

    I have ben using f.lux for a while now and think I kind of got used to the 2700K. And with all those articles i've read on the dangers of too much blue light, i thought why not go even lower when I am using the computer? I actually noticed that it doesn't make much sense to go below that mark when the sun is shining, but I think it's nice to have that option (at least for sunset), because right now where I live the sun isn't shining that intense during the whole day. That way i can adjust it better.

    Another thing is, if I decide to go to bed earlier and artificially make my room dark it's nice to be able to go really low on the scale :)



  • @Marlon-Thomson You know what else has a lot of blue light? The sky, sunlight, and especially overcast weather. Here's two of those things:
    https://fluxometer.com/rainbow/#!id=Outdoors/2PM LA sky

    LED has a bit of a sharper spike in the blue, have a look through the list. The ones with REALLY low (both) yellow and cyan, is OLED. The ones with ONLY a bit lower cyan, (and not as low yellow) is regular LED. In other words, you'll see three, Red, Green, and Blue, for OLED, and something not so distinct like that for regular LED.

    I don't think blue light is bad for the eye, why? Because we've been on this Earth for a helluva long time, and are "just now" finding this out? It just doesn't add up. If that was the case, everyone would have damaged eyes--EVERYONE. So take that stuff with a grain of sand, salt, sugar, or whatever else you want.

    So far it's been established that you'll want bright light during the day, as much as possible. This makes it EASIER to fall asleep SOONER because when you turn down the lights inside, it's much much much darker in comparison, so you're body knows what to do. Also if you happen to turn on a bright light, that will not delay or alter your sleep as much, as if you'd been inside when it's cloudy all day.



  • It's been long established that light can damage the eyes - especially sunlight. Most people are aware of the dangers of long-term exposure to ultraviolet light. More recently blue-violet light in the range of 415 nm to 455 nm has been shown to damage the retina and contribute to age-related macular degeneration. See for example:

    The Lowdown on Blue Light: Good vs. Bad, and Its Connection to AMD

    In terms of circadian rhythms, the eye is most sensitive to blue-green light in the range of around 490 nm, which is relatively safe for the eye. The blue light from a computer screen is mostly in the range of 450 nm. There's enough overlap that it has an effect, especially late at night - which is why we use f.lux. But for someone who wants a bright light source to help with sleep or other issues, a computer screen isn't a very good choice. It contains significant amounts of light in the more harmful blue-violet range, and relatively little in the blue-green range that has the most effect on regulating the body's clock. A better choice would be outdoor light, ideally with appropriate UV and blue-violet filtered glasses, or a lamp made with ~490 nm blue-green LEDs or fluorescents.

    In other words, nobody needs to sit in front of a computer screen for its health benefits, because it doesn't really have any. @Tungsten_smooth , a friendly suggestion, maybe tone it down a bit on telling everyone it's "crazy" to want a warmer colour temperature during the day. If you're not concerned with colour reproduction accuracy, I don't see how it's in any way harmful, and it may help protect against long-term eye damage.



  • @Elhem-Enohpi Have a look at the fluxometer! So you're saying that the blue LED is too sharp in blue, and that Sunlight has less of this?

    Here's the color spectrum of sunlight: https://fluxometer.com/rainbow/#!id=Outdoors/10AM LA sunny
    Here's one for a bright iMac 27": https://fluxometer.com/rainbow/#!id=Thunderbolt 27/6500K-Thunderbolt27

    Here's Philips GoLite: https://fluxometer.com/rainbow/#!id=Light Therapy/Philips GoLite
    As you can see in this example, it's like you said, more cyan/blue, than blue purple, so you may be correct.

    Edit: I think in sunlight, it's not as bad because there are all the other wavelengths to fill in the light, so it's not harsh, it's the same amount of power. In that specific region (450-460) the light does dip down just a tad.

    With regard to screens you do have a good point. There is a sharp point of light in that region and there is nothing to soften the power of it, I've been saying we need AQUA (cyan, blue green) LEDs to combat that spike of blue that limits the color rendering of the cyan and red. It would help a lot with warm white especially.


  • f.lux team

    It isn't crazy, but seeing warm light all day long may not be especially healthy for everyone either. Staring at screens 24 hours a day and staying in perpetually dim light is probably pretty bad for both your eyesight and your sleep.

    No one knows all the answers here. We think generally it is better to have more information - as long as it's understandable and it's not causing more fear. So we want people to understand how much and what kind of light you're getting (and should be getting). Someone with a family history of AMD has different light needs than someone who does not, and for someone with retinitis pigmentosa, any amount of bright blue light at any time of day can be dangerous.

    In terms of photons hitting retina, you're seeing much more blue light walking outside for five minutes than you do sitting at a screen all day. But which one is less healthy? Staying indoors all day isn't that healthy for most people since the light we see indoors is typically dim. Staying in the dark can make your body even more sensitive to the effects of light at night. And the eyes have a circadian rhythm of their own, so what is comfortable to see in the middle of the day is usually not comfortable before bed.

    Because the body reacts to light very differently throughout the day, the best settings for you at 10AM are not the same as the best settings at 10PM. Each person needs to find out what is right for their life and health and goals. It's complicated stuff, but hopefully we will be able to provide some useful tools and visualizations to help.



  • @lorna Thanks for that. I agree that there are no simple answers, and different people have different needs. F.lux is great, not only because it's helped me improve my sleep, but also to find out a lot about the subject. Of course you and Michael are light-years ahead of me :-) I learn something new almost every time I come here.

    Living in the Dark North, I've known for some time about the importance of light during the day, and f.lux has helped me better understand that too. I know from experience that being in dim light all the time can make me feel depressed and interfere with my sleep. But I have friends who don't seem to be bothered by it. Perhaps if your ancestors have been living here for 20,000 years, you're more equipped to deal with it.

    Probably looking at a bright 6500K LED screen helps to some extent, but I think there are other, better options. Like going out for a long walk every day. My point about having a warm screen during the day is that it's not terribly different from just turning the computer off. I think it's easy to get the misunderstanding that "blue light wakes you up, and orange light makes you sleepy". As long as you get enough light exposure elsewhere, seeing warm light during the day isn't harmful to your sleep patterns, in the way that seeing cool light at night is. It took me some time to understand that.

    I've never been any kind of health nut, but since my hair turned grey, I've been more aware of it. Several people in my family have needed eye surgery, and it's not something to look forward to. I've had some success with adjusting my light exposure in terms of sleep, and now I want to work a bit on limiting long-term eye damage. That will probably include finding a pair of glasses with both ultraviolet and blue-violet coatings, replacing my standard daylight LED bulbs with something in the blue-green range, and a warm setting on my screen whenever I'm not doing something that needs colour accuracy. It's an interesting learning process!



  • I am confused about this problem in a long time ago, but now I have got answers. Thank you.


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