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Comment by ItsMe000001 | Hacker News Reader

I've been using it for a long time but I have a question.

Sometime ago somebody on reddit or here on HN claimed in a comment that f.lux does not actually reduce the amount of blue light if you measure it. Unfortunately I never saw any replies or sources, and looking for discussions about that subject were unsuccessful.

Does anybody have any actual knowledge that could support or refute that claim?

PS: I hate it when people make claims like that and don't even attempt to support it. Now I'm still looking for an answer months later.

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I find it hard to imagine how the screen could look yellowish while still outputting a lot of blue, but you can actually check it - look at the blue sub-pixels with a magnifying glass or your phone camera and see if they actually dim.

Could it be that on lcd screens you can't eliminate blue light fully? Tested this with comour filters on iphone 8. Fully red, still emits blue at angles when held to a wall. Apple watch with red flashlight on doesn't do this. (It's oled)

I think it was in f.lux's blog that while f.lux does reduce amount of blue light, apple's built-in night mode (the one on your iphone for example) didn't.

Can't find source now.

I started searching around. Could it be this reply within forum? https://forum.justgetflux.com/topic/4056/blue-light-screen-b...

Contains a link where a graph (which I don't understand) is almost identical with and without sleep shield.

  lorna F.LUX TEAM Aug 17, 2017, 5:48 AM
  And here is the same iPad with one of the many filters that claim to help sleep (unless they are a deep orange, most of them do absolutely nothing): https://fluxometer.com/rainbow/#!id=iPad%20Pro/6500K-iPad%20Pro&filter=filter/SleepShield

But that SleepShiled looks like is a physical device actually.

https://www.amazon.com/SleepShield-iPad-Blue-Light-Filter/pr...

https://forum.justgetflux.com/post/12848

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