Campfires are not artificial light. This is about blue light after all. You need to show some data to back your statements besides hand-waving all existing studies in one swoop.
Campfires are artifical as in they are not the sun, and people were exposed to their radiation for millenia. A fire obviously emits most of its electromagnetic radiation in the IR band, but it the emission goes down right into UV. This is not exactly rocket science, just point a UV/Vis spectrometer at a fire and see for yourself.
I'm not quite sure why you think I should provide data - I'm not the person postulating the effect of blue light. But anyway. You can find examples of the sun's illuminance all over the net, for example Wikipedia has a list here: https://en.wikipedia.org/wiki/Illuminance
Illuminance usually only covers the VIS part of the EM spectrum, so all of about 380-700nm. So 1/4 to 1/3 of that is the cold light part.
The radiation emmited from a heat source can be determined using Planck's law. A campfire is about 1400K. Here you can see that the higher the temperature, the more the maximum radion shifts into smaller wavelengths: https://www.spektrum.de/lexika/images/geo/f4f1653_w.jpg
So obviously the sun with about 6000k has way more UV and blue light parts, but a campfire is still hot enough that the absolute amount of blue light emitted trumps every phone screen. Yes, probably more than 95% will be IR, but than again the overall luminocity of a campfire is about 10kW.
As to my criticisms regarding most studies about the effects of light: You can look them up yourself, most of them apply to the studies linked at f.lux's research links: https://justgetflux.com/research.html
For example the top two studies there:
"Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans" used 8h room light and didn't check for blue light at all. Neither did they look at actual sleep patterns.
"The human circadian system adapts to prior photic history" : 6.5h of exposure, no blue light specifically, only melatonin, no actual sleep measurments.
Again: I'm not the person making claims here. I would be delighted to see some proper studies showing the effects of blue light.
You are indeed making claims, and worse, generalizing a “lack of evidence” from a handful of unrelated studies you picked. It’s kinda obvious that not all of the studies linked in the flux page are about blue light specifically, but how electronic device usage affects health. The effect of blue light is widely accepted in the scientific community and not some kind of fringe theory.
On your campfire rant, first, luminosity is an astronomy measure, what matters for humans is the perceived light (lumens); nobody stares at a campfire directly and the little light bounced from the surroundings has very little blue; on the other hand, you literally stare non-stop for hours at the blue light from your phone, which makes the amount it emits a lot more relevant.
Well then, feel free to provide the research. You can then also send it directly to UK's General Optical Council because they actually sue companies who claim health benefits from blue light filtering [1] because there is no evidence for real-world effects. Or the EU's Scientific Committee on Health, Environmental and Emerging Risk, because they, too, say that there is no scientific base for the claim of real-world effects [2, page 90]. Or Cochrane review, who say that there is no health effect in case of macula degeneration [3].
Also please don't get personal. My campfire illustration was not a rant, it was an illustration of humans using light after sunset. It is a fact that they did so for millenia. It is also a fact that a 1300K hot fire emits blue light and even UV light.
And luminosity (lux) is just luminous flux (lumens) per square meter. Astronomers use that because luminosity is the measure used to compare different light sources. If comparing e.g. a ceiling light and a phone screen one uses luminosity because that makes both light sources easier to compare. It is also the measure most research on light effects work with. You could of course multiply the 1000lux of a bright phone display with its surface area in square meters if you prefer to calculate in lumens.
