I don't know what forum to put this. Why does F.lux not filter out ALL blue light?



  • Why does F.lux not completely filter out ALL blue light? You cannot filter out all blue light and still see the colour blue. Even at 1200k I can still clearly see the colour blue on my monitor. Is there no way to filter out all blue light using software? I have amber Uvex S1933X Skyper Safety Eyewear glasses that completely block out the colour blue, would be nice if I didn't have to wear them while looking at my devices.


  • f.lux team

    Every mode from 1900K and lower filters all "blue pixels" from your display.

    If you're trying to filter all alerting light you also need to filter all the green too. 1200K lets just a little bit of this through, which massively improves your ability to use your computer at night, at a very tiny cost to extra light you see.

    However--there are two more things that mean (in reality) f.lux doesn't filter all blue:

    1. LCD screens are imperfect and let through some of the backlight color. For most displays this is <0.1% though.

    2. Many panels are trying to "match" sRGB and allow through some blue and green on purpose, even when displaying saturated red. This is because the red primary they would achieve otherwise is too saturated. (You'd prefer they use a "wide red" primary but instead they mix in some blue and green.)

    But in the end, the circadian effects of low levels of light like this seem to be extremely small. Blocking 90% is probably good enough to keep screens from messing up sleep.

    If you want to preserve night vision, try out our Darkroom mode while dimming your screen a lot. It'll probably make you happier anyway.

    Since you're posting in the f.luxometer forum, there is a lot of data over there to figure out what is going on with a variety of displays.

    https://fluxometer.com/rainbow/



  • Another thing to consider is the brightness of light. Even with pure red light, dimmer is better.

    Also, there is indeed blue light bleeding from a monitor. I see it when I have a white object near the base of my monitor (in front of my monitor) or a shiny silver reflective object in that spot. Even with 1200K or Darkroom Mode, I still see the blue light reflecting off of the white or silvery-reflective object.

    Try it: in a very dark room with f.lux set to 1200K, put something very white right in front of your monitor at its base. You might notice the blue standing out against all the red coming straight at you. Its like blue is being beamed up and down from the monitor, but not straight out at your eyes. It can almost appear as though the bottom is still emitting 6500K at a downward angle (and at an upward angle).



  • @TwoCables If the OLED people can fix the PWM backlighting, then it will solve this problem completely!



  • @timpster said:

    @TwoCables If the OLED people can fix the PWM backlighting, then it will solve this problem completely!

    The market does have flicker-free LED monitors.



  • @TwoCables Yeah, but I'm talking about "organic" LED, OLED, which currently has a PWM diagonal flicker that I can see very well. It's terrible!

    In fact, if you look up on youtube, Samsung Note 4 auto brightness outside, you'll see the flicker on camera. For me it's not black lines, it's like... a fuzziness constantly screwing up my reading, video watching etc, it's just awful.



  • Everything has flicker though. All of your light bulbs, your monitor, etc.


  • f.lux team

    If you're flicker sensitive it's dreadful because the thresholds for some consumer applications are too low. I haven't been scientific about figuring this out, but I can see over 200 fps. If the PWM is a square wave it makes me feel physically ill. Elevator retrofits are often the worst offenders for some reason. And there's one restaurant nearby that I can't go into after dark because they retrofitted their LEDs with square wave PWM. It is like trying to walk through a strobe light for me, and everyone else is just eating their noodles, NBD. https://en.wikipedia.org/wiki/Flicker_fusion_threshold



  • @lorna Yeah, I can clearly see my phone flicker in my mirror from.... 7 -9 feet away at night, like how the hell did they let that pass? And then if you run dimmer apps, it's just stupid visible. Why haven't they gotten it right!!

    Also I can see the flicker on stock low brightness from 10 inches away, which puts a shimmer on the text and prevents me from reading it. It's exactly as bad (or maybe worse) than PWM on normal LED, not sure yet, but it's down right awful.


  • f.lux team

    @timpster People are looking into it, so I'm hopeful. We're what they call "flicker sensitive people" hah. Lots of goodies in here: http://energy.gov/sites/prod/files/2015/11/f27/miller_gaines_flicker_portland2015.pdf



  • Last visit at LightFair I was aghast that most LED driver modules operate with significant 120Hz flicker as do Seoul Semiconductors Acrich 120vac straight off the line modules and they don't seem to care! Yikes. The min flicker frequency for our lamp is 2KHz at minimum brightness <1% and at full brightness is in the 10's or 100's of kHz. Next time you are at Home Depot or anywhere there is an LED rapidly wave your hand in front of it and look for stroboscopic effect. This is a good way to detect flicker. I just checked out my iPhone that way and now I will have to try with a 'scope and a photocell. Thanks for giving me another reason to dislike my phone :(



  • @lorna Great slide deck. Filed it in two different libraries :) Thanks!



  • @arioda said:

    Last visit at LightFair I was aghast that most LED driver modules operate with significant 120Hz flicker as do Seoul Semiconductors Acrich 120vac straight off the line modules and they don't seem to care! Yikes. The min flicker frequency for our lamp is 2KHz at minimum brightness <1% and at full brightness is in the 10's or 100's of kHz. Next time you are at Home Depot or anywhere there is an LED rapidly wave your hand in front of it and look for stroboscopic effect. This is a good way to detect flicker. I just checked out my iPhone that way and now I will have to try with a 'scope and a photocell. Thanks for giving me another reason to dislike my phone :(

    I've never seen flicker on an LED lit screen, well, again unless it uses PWM, but I've not seen it on phones, until every damn android phone went to OLED, then I see it way too much.

    Anyway, that part about having very high frequency on the LEDs, I can't thank you enough. I didn't get a couple on the kickstarter, as it was decided that we'll wait until it's fully ready, just so there's no issues and such. So I'll get one next year, I'd have to wait a bit anyway so I don't mind if it cost more, I'll support you!

    Also back to the LEDs at the store, I don't have to wave my hand, I can look straight at it and see it. It's ridiculous--can they just hire me and let me fire anyone who says that 120hz is O.K.? I really just want to fire all of them! Also whoever wrote the spec on it, REALLY wanted to push it up to 150hz, but guess how that worked out.



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