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An explanation might be LED lighting. Sunlight, candle-light and resistive filament lights (incandescent) have a broadband spectrum. Through most of history we

An explanation might be LED lighting. Sunlight, candle-light and resistive filament lights (incandescent) have a broadband spectrum. Through most of history we've viewed the world lit by these sources. Moving to fluorescent lights causes spectral quantisation as the frequencies are due to electronic band transitions in the gas. The phosphor absorbs and re-emits energy in different bands that fills out the spectrum but it's still really strange, with missing bits. When fluorescent lights first became popular people complained of headaches from the strange spectrum. They are disfavoured in certain industrial applications because they make some colours harder to see. Semiconductor lighting is even worse in this regard. Radiative re-emission in valance holes emits line spectrums. Only by combining these do we trick the eye into seeing "white light". Recently we've got good at blending doping agents to give mixed spectrums that approximate daylight. If these forms of electronic lighting have holes in their spectra, perhaps that's why an analysis of a corpus of photos shows a change in spectrum over time?

jan_Inkepa 4y ago
I have real problem with colour-perception in LED lighting - board game evenings are tricky when I can't tell the piece colours apart so well. Feels like it's just me though...
- Broken_Hippo 4y ago
  A couple weeks ago, I had the chance to play board games by candlelight. I was in a cabin in the woods. And trust me, it would be much better with LEDs though obviously not perfect. Sometimes the colors just aren't different enough to easily tell apart. It seems like an issue that should be fixed.
- dangrie158 4y ago
  Maybe the problem is cheap LED lamps. Check for a high color rendering index [1] (CRI >>90) [1]: https://en.wikipedia.org/wiki/Color_rendering_index https://en.wikipedia.org/wiki/Color_rendering_index
  - MgB2 4y ago
    Exactly, if you get nice CRI 95 lamps you are unlikely to have a noticeable problem with color rendition. But still beware, the CRI printed on the box (Ra) is kind of flawed since it is measured on unsaturated colors and does not include information about color renditions of red objects. You would have to look at the R9 value as well.
zokier 4y ago
> Only by combining these do we trick the eye into seeing "white light" Vast majority of white LEDs are phosphor based and not color-mixing
- titzer 4y ago
  The decorative programmable-color LED strips and such use RGB LEDs.
  - tomashubelbauer 4y ago
    Not always, many are RGBW since the sole white LED consumes less power than the RGB LEDs shining together to produce white (I believe so at least) and the white color coming off the single white LED is nicer than the mixed color.
  - TremendousJudge 4y ago
    This is terrible for people with glasses btw -- induces much more chromatic aberration than other light sources, and is very distracting and hard to ignore. At the edges of the field of view objects get very clearly separated, with the blue part usually being the most noticeable.
    - titzer 4y ago
      Yes, completely agree. I primarily wear glasses now and I hate seeing 2 or three ghost images.
pflanze 4y ago
> re-emission in valance holes Are you talking about single-colour LEDs? Since white LEDs use a "phosphor", just like fluorescent lights, that convert blue or UV light. In fact I thought that the phosphors used by LEDs today are much better than those used by fluorescent lights. Maybe you're talking about RGB lights, which combine separate reg, green and blue LEDs so that the colour mix can be changed. But even then I thought, unlike lasers, LEDs are not using single frequencies but relatively wide bands (but will still leave gaps between the red, green and blue colours).
- nonrandomstring 4y ago
  > white LEDs use a "phosphor", just like fluorescent lights Wow. I didn't know that. So I guess the junction actually emits UV which is converted to visible spectrum? Does that mean they're bad for your eyes if some UV leaks out? How I thought it worked is that different doping materials are blended in the junction to get a mix of frequencies. Maybe that's impossible. And yes, sure for RGB clusters the spacing is obvious even to my eyes.
  - pflanze 4y ago
    > Does that mean they're bad for your eyes As far as I can see from distributors, most white LEDs today are using a blue light emitter, so there's no issue with UV. When using white LEDs that use an UV emitter, some glass covering is needed to catch the remainder, from what I've heard from a friend (I've never actually built an LED lamp myself). But it appears that blue LEDs are much more efficient than UV ones and that probably explains why normally white LEDs use blue emitters. More information here (confirming what I just wrote): https://en.wikipedia.org/wiki/Light-emitting_diode#White https://en.wikipedia.org/wiki/Light-emitting_diode#White PS. I've been looking into these things to some extent because of all the issues with commercial LED lamps (short life, AC or PWM flickering, colour rendering), and have been thinking of mixing more LEDs together (various single colour ones together with various phosphor-employing ones) so as to mix a more ideal spectrum myself, but I haven't gotten around to actually executing that plan.
  - MgB2 4y ago
    For normal lighting LEDs the diode itself usually emits blue light (440-460 nm). Most of the blue photons are then absorbed by the phosphor or phosphors and reemitted at longer wavelengths (yellow-green to red). This converted light mixed with the remaining blue light gives the white color impression. So no UV, although there are some concerns about the hazards of blue light. But if you ask me, you get much more blue light onto your retinas by just going outside on a sunny day than you'd ever get from normal LED lighting.
amalcon 4y ago
This seems like it would be pretty testable. We still take a lot of photos under sunlight. If light sources are the cause, then the effect should disappear if we look only at such photos.
MgB2 4y ago
As others have pointed out, LED lights for general lighting (not those RGB strips for accent lighting) use phosphors with very broad emission bands. Unlike fluorescent lamps, they don't have big gaps in the spectrum. Just a dip in the cyan region. Just make sure to buy stuff with high CRI, preferably 90 or more, and you'll be fine.

jan_Inkepa 4y ago

I have real problem with colour-perception in LED lighting - board game evenings are tricky when I can't tell the piece colours apart so well. Feels like it's just me though...

Broken_Hippo 4y ago
A couple weeks ago, I had the chance to play board games by candlelight. I was in a cabin in the woods. And trust me, it would be much better with LEDs though obviously not perfect. Sometimes the colors just aren't different enough to easily tell apart. It seems like an issue that should be fixed.
dangrie158 4y ago
Maybe the problem is cheap LED lamps. Check for a high color rendering index [1] (CRI >>90) [1]: https://en.wikipedia.org/wiki/Color_rendering_index https://en.wikipedia.org/wiki/Color_rendering_index
- MgB2 4y ago
  Exactly, if you get nice CRI 95 lamps you are unlikely to have a noticeable problem with color rendition. But still beware, the CRI printed on the box (Ra) is kind of flawed since it is measured on unsaturated colors and does not include information about color renditions of red objects. You would have to look at the R9 value as well.

zokier 4y ago

> Only by combining these do we trick the eye into seeing "white light" Vast majority of white LEDs are phosphor based and not color-mixing

titzer 4y ago
The decorative programmable-color LED strips and such use RGB LEDs.
- tomashubelbauer 4y ago
  Not always, many are RGBW since the sole white LED consumes less power than the RGB LEDs shining together to produce white (I believe so at least) and the white color coming off the single white LED is nicer than the mixed color.
- TremendousJudge 4y ago
  This is terrible for people with glasses btw -- induces much more chromatic aberration than other light sources, and is very distracting and hard to ignore. At the edges of the field of view objects get very clearly separated, with the blue part usually being the most noticeable.
  - titzer 4y ago
    Yes, completely agree. I primarily wear glasses now and I hate seeing 2 or three ghost images.

pflanze 4y ago

> re-emission in valance holes Are you talking about single-colour LEDs? Since white LEDs use a "phosphor", just like fluorescent lights, that convert blue or UV light. In fact I thought that the phosphors used by LEDs today are much better than those used by fluorescent lights. Maybe you're talking about RGB lights, which combine separate reg, green and blue LEDs so that the colour mix can be changed. But even then I thought, unlike lasers, LEDs are not using single frequencies but relatively wide bands (but will still leave gaps between the red, green and blue colours).

nonrandomstring 4y ago
> white LEDs use a "phosphor", just like fluorescent lights Wow. I didn't know that. So I guess the junction actually emits UV which is converted to visible spectrum? Does that mean they're bad for your eyes if some UV leaks out? How I thought it worked is that different doping materials are blended in the junction to get a mix of frequencies. Maybe that's impossible. And yes, sure for RGB clusters the spacing is obvious even to my eyes.
- pflanze 4y ago
  > Does that mean they're bad for your eyes As far as I can see from distributors, most white LEDs today are using a blue light emitter, so there's no issue with UV. When using white LEDs that use an UV emitter, some glass covering is needed to catch the remainder, from what I've heard from a friend (I've never actually built an LED lamp myself). But it appears that blue LEDs are much more efficient than UV ones and that probably explains why normally white LEDs use blue emitters. More information here (confirming what I just wrote): https://en.wikipedia.org/wiki/Light-emitting_diode#White https://en.wikipedia.org/wiki/Light-emitting_diode#White PS. I've been looking into these things to some extent because of all the issues with commercial LED lamps (short life, AC or PWM flickering, colour rendering), and have been thinking of mixing more LEDs together (various single colour ones together with various phosphor-employing ones) so as to mix a more ideal spectrum myself, but I haven't gotten around to actually executing that plan.
- MgB2 4y ago
  For normal lighting LEDs the diode itself usually emits blue light (440-460 nm). Most of the blue photons are then absorbed by the phosphor or phosphors and reemitted at longer wavelengths (yellow-green to red). This converted light mixed with the remaining blue light gives the white color impression. So no UV, although there are some concerns about the hazards of blue light. But if you ask me, you get much more blue light onto your retinas by just going outside on a sunny day than you'd ever get from normal LED lighting.

amalcon 4y ago

This seems like it would be pretty testable. We still take a lot of photos under sunlight. If light sources are the cause, then the effect should disappear if we look only at such photos.

MgB2 4y ago

As others have pointed out, LED lights for general lighting (not those RGB strips for accent lighting) use phosphors with very broad emission bands. Unlike fluorescent lamps, they don't have big gaps in the spectrum. Just a dip in the cyan region. Just make sure to buy stuff with high CRI, preferably 90 or more, and you'll be fine.