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The sun is actually white. The yellow tint is due to Rayleigh Scattering in the atmosphere. When the sun is high in the sky there's less scattering and it appea

The sun is actually white. The yellow tint is due to Rayleigh Scattering in the atmosphere. When the sun is high in the sky there's less scattering and it appears whiter, when it's low there's more scattering and appears yellow/orange. Here's a better explanation: https://physics.stackexchange.com/questions/47694/why-is-the-colour-of-sunlight-yellow https://physics.stackexchange.com/questions/47694/why-is-the...

gmueckl 5y ago
This is just wrong. The surgace of the sun is around 5700K and rhe emitted light follows the back body spectrum for that temperature. And that has a massive yellow peak. See https://en.m.wikipedia.org/wiki/File:EffectiveTemperature_300dpi_e.png https://en.m.wikipedia.org/wiki/File:EffectiveTemperature_30... for the data. This is measured outside the Earth's atmosphere. Rayleigh scattering does come into play, but it is way less important. As I said, human vision has a kind of adaptive white balance that cancels out peaks like this to some extent. It also does that for artificial light sources with uneven spectra (neon light, blueish white LED lights...). [Side note: this is also the reason why cameras have adjustable white balance. A picture taken by a neutral sensor under some artificial lights is perfectly correct, but looks color tinted and wrong to the human eye afterwards, because the eye under the same conditions has a shifted white point.] Why is this important? If you set up a light source in a renderer, you often get a pretty naive equal energy white as a default, which is simply not what you need for sunlight, even at noon under a clear sky.
- bjelkeman-again 5y ago
  You see how the brain does white balancing quite clearly when working with LED lights optimised for salad, for example. The light has very little green in it and looks nearly pink. After a few minutes it looks less pink and nearly normal (depending on the lamps). Then go outside in daylight and everything suddenly look green, which takes a minute to go back to normal. The brain adds the green it perceives to be missing, and removes it again when it isn’t needed.
  - nine_k 5y ago
    An even easier example is the typical home light which is very peach-tinted (at 2500K), as seen from outside/ But inside the light feels entirely normal white after a very short time.

gmueckl 5y ago

This is just wrong. The surgace of the sun is around 5700K and rhe emitted light follows the back body spectrum for that temperature. And that has a massive yellow peak. See https://en.m.wikipedia.org/wiki/File:EffectiveTemperature_300dpi_e.png https://en.m.wikipedia.org/wiki/File:EffectiveTemperature_30... for the data. This is measured outside the Earth's atmosphere. Rayleigh scattering does come into play, but it is way less important. As I said, human vision has a kind of adaptive white balance that cancels out peaks like this to some extent. It also does that for artificial light sources with uneven spectra (neon light, blueish white LED lights...). [Side note: this is also the reason why cameras have adjustable white balance. A picture taken by a neutral sensor under some artificial lights is perfectly correct, but looks color tinted and wrong to the human eye afterwards, because the eye under the same conditions has a shifted white point.] Why is this important? If you set up a light source in a renderer, you often get a pretty naive equal energy white as a default, which is simply not what you need for sunlight, even at noon under a clear sky.

bjelkeman-again 5y ago
You see how the brain does white balancing quite clearly when working with LED lights optimised for salad, for example. The light has very little green in it and looks nearly pink. After a few minutes it looks less pink and nearly normal (depending on the lamps). Then go outside in daylight and everything suddenly look green, which takes a minute to go back to normal. The brain adds the green it perceives to be missing, and removes it again when it isn’t needed.
- nine_k 5y ago
  An even easier example is the typical home light which is very peach-tinted (at 2500K), as seen from outside/ But inside the light feels entirely normal white after a very short time.