@alexncfc said: I am very interested by the concept of filtering out the blue light, but I am noticing that since using these blue light filters on my PC and phone, I have a banging headache. I actually feel strained looking at the screen with the filter on (when I turn it off temporarily, admittedly it's even worse, it feels like I am being blinded!) Has anyone experienced similar issues such as eye strain and headaches when using the filter? Also, has anyone noticed that they feel they sleep better and feel refreshed etc since using f.lux? The eye strain and headaches you are experiencing may be caused by setting the screen brightness too low for your eyes to focus comfortably since warmer colors have lower intensity. Try adjusting the brightness a little higher than the current setting that is causing the strain. You can also adjust the lighting in the room that you are using the device in to a brightness that is relatively lower than your screen. Also avoid having just certain areas lighted in your room, like a lamp that only lights up a small area. Non uniform lighting around you can also affect the eyes. Hope these helps rid you of your ailments. Cheers.