Michael from f.lux: This research is from a very talented group of researchers, but it is unclear if it will translate from nocturnal mice to humans (as others have said). The evidence in humans is mixed, but it either shows no effect or a tendency in the other direction. There is a study in the same issue (Spitschan) that says there is no effect in humans.
1. First, the study does not question the contribution of melanopsin (the blue-cyan opsin that got everyone talking about "blue light") - it asks a more subtle question: when you hold melanopsin stimulation constant, what does the remaining light do and why? Here they are finding whether the cones oppose or boost melanopsin based on color signals. But regardless of how this works in humans, we should still expect bright-enough blue light at night to be stimulating, because of the response due to melanopsin.
2. Holding the melanopic portion of a light constant is not something we usually do. For most lights we have today, the "blue" lights would be considerably dimmer than the "yellow/red" ones if we did this. When we compare lights of equal visible brightness, the yellow ones are known to have less effect on human melatonin suppression [Chellappa 2011].
3. The evidence in humans is mixed, but it actually goes the other direction (saying blue is more stimulating), or there is no clear effect. In the same issue, a study on humans by Spitschan found a negative result on whether or not S-cone contrast has an effect: https://www.cell.com/current-biology/fulltext/S0960-9822(19)...
3b. Other research (in monochromatic and polychromatic light) finds that humans are more sensitive to blue light than melanopsin would suggest. See a list below.
4. We're all still trying to explain how the transition to dusk is blue/purple, while our own lighting doesn't do that. We have built our lighting to be relatively bright, but warm. It is not "natural" to extend the day like we do, but it likely would not help anything to make the lights more blue, unless they were quite a lot dimmer, or used very novel spectra.
Here is a list of references for the evidence +/- blue sensitivity (not melanopsin) in humans:
2. The Spitschan study from this same issue of Current Biology says there is no effect in either direction when comparing 83x S-cone contrast. The lights here are "pink" (which has a lot of blue) and "orange" which has very little. https://www.cell.com/current-biology/fulltext/S0960-9822(19)...
4. There is one important study in humans (Gooley 2010) that says we can be more sensitive to 555nm light after two days in dim light, so that mirrors this study. But this is not exactly comparable to the study cited here due to sensitization: it stands on its own due to the duration of the experiment.
It would be interesting if we could find some "truth" to the idea that twilight colors affect human circadian entrainment - it has been a recurrent idea for many years. We finally have the technology to target melanopsin separately from the S-cone (see Spitschan's work for an example).
For the press these results get, you'd be surprised that there has been extremely little research funding for most of these things in the last ten years. In a way, I hope that mixed results like these might help! How light affects us at lower levels, and how different we are from each other is not "solved" at all, so there is still a lot of work to do.
It's quite nice seeing someone who has a entrenched interest promoting awareness of new evidence, that—whilst it may hurt their own stake—is important to furthering humanity's understanding and getting to the ground level of what the truth actually is.
We just so obviously need more behavior like this. It's taboo in our culture to change a stance you once publicly made and there are so many things wrong with that. To not change your mind is to not be in dialog with the world and all the new evidence that's accumulating there within.
Personal guess is that blue light probably isn't conducive to staying circadian-aligned, but like the parent am open to new evidence.
Regardless of the actual effect on sleep, the "night light" modes for screens very much reduces the eye strain I feel. So much so that I've enabled some version of it on every screen I use, permanently, not only at night.
I find it much more pleasant and comfortable. Interestingly, I've gotten so use to it my brain compensates for the color change and it looks pretty normal to me.
Our eyes have absolutely incredible colour correction, running all the time and so well that we just don’t notice it; except for some edge cases where it gets tricked (eg the whole dress saga, or optical illusions you can find).
At first I had to keep checking the settings because I thought it had turned off. But when I turned it off it looked extremely blue and painfully bright. Even looking at a white screen I can't notice the orange tint at all anymore. It's pretty amazing.
I am always reminded of it when accidentally I go fullscreen mode and my flux turns off. It really hits you how bright the screen gets (and I am not using full filter, I like to keep colour distortion at bay).
Even if the blue light is a myth I will keep on using flux.
I agree. Even if blue light wouldn't interfere with sleep in any way, the glow of the screen in the evening feels so straining to eyes that just for this reason I like to use f.lux.
I have f.lux running on my desktop and laptops, and the way it helps me "come down" in an evening is amazing. I don't know why I never thought to donate before, but your comment made me think of it, and I'm going to give a donation right now!
Thanks for the awesome software, but I have to ask why it keeps asking me for my location every time I boot up my system. I use a custom setting that’s constant throughout the day. Just thought I’d give it a shot and maybe someone from flux will take notice
Most people don’t move around significantly. One way to find this is by detecting networks: if I’m plugged into Ethernet or connected to the same wifi, I’m probably at the same place. Please do not ask me for my location.
We only prompt if your timezone offset changes (traveling), or if you've never set things up. Something in the parent's configuration is triggering "never set". We have not used BSSIDs for this because some corporate and campus users roam between hundreds of APs, so it would be much more invasive (or we'd have to chat on the network to figure out that nothing had changed).
1. First, the study does not question the contribution of melanopsin (the blue-cyan opsin that got everyone talking about "blue light") - it asks a more subtle question: when you hold melanopsin stimulation constant, what does the remaining light do and why? Here they are finding whether the cones oppose or boost melanopsin based on color signals. But regardless of how this works in humans, we should still expect bright-enough blue light at night to be stimulating, because of the response due to melanopsin.
2. Holding the melanopic portion of a light constant is not something we usually do. For most lights we have today, the "blue" lights would be considerably dimmer than the "yellow/red" ones if we did this. When we compare lights of equal visible brightness, the yellow ones are known to have less effect on human melatonin suppression [Chellappa 2011].
3. The evidence in humans is mixed, but it actually goes the other direction (saying blue is more stimulating), or there is no clear effect. In the same issue, a study on humans by Spitschan found a negative result on whether or not S-cone contrast has an effect: https://www.cell.com/current-biology/fulltext/S0960-9822(19)...
3b. Other research (in monochromatic and polychromatic light) finds that humans are more sensitive to blue light than melanopsin would suggest. See a list below.
4. We're all still trying to explain how the transition to dusk is blue/purple, while our own lighting doesn't do that. We have built our lighting to be relatively bright, but warm. It is not "natural" to extend the day like we do, but it likely would not help anything to make the lights more blue, unless they were quite a lot dimmer, or used very novel spectra.
Here is a list of references for the evidence +/- blue sensitivity (not melanopsin) in humans:
1. The Thapan study from 2001 indicates extra blue-light sensitivity in addition to melanopsin. Lights are seen for a half hour at night. https://doi.org/10.1111/j.1469-7793.2001.t01-1-00261.x
2. The Spitschan study from this same issue of Current Biology says there is no effect in either direction when comparing 83x S-cone contrast. The lights here are "pink" (which has a lot of blue) and "orange" which has very little. https://www.cell.com/current-biology/fulltext/S0960-9822(19)...
3. The Brainard 2015 study compares 4000k to 17000k lights: at the same "melanopic" level the 17000k lights do a lot more melatonin suppression: https://jdc.jefferson.edu/cgi/viewcontent.cgi?article=1081&c...
4. There is one important study in humans (Gooley 2010) that says we can be more sensitive to 555nm light after two days in dim light, so that mirrors this study. But this is not exactly comparable to the study cited here due to sensitization: it stands on its own due to the duration of the experiment.
It would be interesting if we could find some "truth" to the idea that twilight colors affect human circadian entrainment - it has been a recurrent idea for many years. We finally have the technology to target melanopsin separately from the S-cone (see Spitschan's work for an example).
For the press these results get, you'd be surprised that there has been extremely little research funding for most of these things in the last ten years. In a way, I hope that mixed results like these might help! How light affects us at lower levels, and how different we are from each other is not "solved" at all, so there is still a lot of work to do.