Melanopic Light (vs. white)

  • Hello there! I've been trying to find out what the following setting or information does but my search came up empty. In the "About f.lux" window, there is a button with a clockwise arrow and next to it words that say "Melanopic Light (vs. white)". What is the button supposed to do and what is the figure provided supposed to indicate?


  • Hey there - thanks for the question!

    The brightest your monitor can get is when it is displaying a white page (without f.lux). f.lux changes the color of that whitepoint, but the content on your screen can also affect the amount of light getting to your eyes.

    So here, we are trying to show two things:

    1. what portion of the "non-visual" light f.lux is removing and
    2. how the current screen content reduces that light

    These two numbers are multiplied together to give the value shown.

    So if f.lux is removing 80% of the light and the screen is all white, you'd see "20%". But then if you are watching a dark movie, maybe the value shown might be "5%" (or something like that).

    For most displays, if this number is in the single digits (<10%), it will be "below threshold" for melanopsin (the sensor in your eye that accounts looks for daylight) - i.e. they won't have much effect on the circadian system. For a 27" display or multiple monitors, you'd want it to be a little bit less.

    Dimming your screen is also very important, and we don't show that here.

  • Thanks for the info. I don’t think I fully get the explanation.

    I’m rather crude terms, do you mean that the figure shown is how much percentage of visible light remains after f.lux has made its shift? So if the figure says 30%, it means it’s reduced the visible light by 70%. (Ok, my own re-explanation doesn’t even make sense to me; could you try again? :) )

    Btw, I have a 27” Thunderbolt monitor.


  • It's the opposite - the amount of light left.

    It is weighted in terms of the "blue" light that affects the circadian system.

    The 27" thunderbolt is very bright. I have one but I dim it a lot at night.

  • @herf OK, thanks for the info!! Lots to digest.

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