[oxag3n]

I have a related but deeper question about sun and colors:

Sunlight in space is considered white. When it reaches earth surface, it's considered a warmer color. Why human eyes that never (during evolution) saw sunlight without the atmosphere, consider it true white, and not colder color?

[16bytes]

Is it considered a warmer color on the surface?

Mid-day sun in a clear sky is very white, in the 5k-6k color temperature range. It's hard to get a sense of how white it is because of how bright it is. In fact, the color temperature on the surface can be even higher than in outer-space!

Compare this to a "warm" light bulb, which is around 2.5K. Sunrise/sunset is also around that range.

Perhaps the "warm color" sun mindset comes from the only times that people can look directly at it. That is to say, around sunrise or sunset.

[zehaeva]

I think at this point you need to consider how the human eye see color. It's not like each wavelength gets picked up and then communicated perfectly.

(I'm going to skip over some basic stuff, and use some generalities)

Each Cone in the eye responds to a range of frequencies. This means that things that unless it's on the extreme low, or high, end of the frequencies that the human eye can discern you are going to have two, or all three, Cone types responding. The strength of those responses is what your brain uses to interpret the color that you see.

The real problem is that out in space there is no attenuation of sunlight, it's bright. Super crazy bright. It basically overloads all of your Cones, and Rods, all at once, there is no way for your brain to find a signal of "oh there's more higher wavelengths here so interpret bluer than normal" because all of the signals got maxed out. If you max out all of the signals, you get white. It doesn't matter that in absolute terms there's more blue, the lower and mid frequencies are also maxed out.

[mncharity]

IIUC, saturation is a (not uncommon) distractor here. As you get the same observation when desaturated by a neutral filter. Even on the "ground" with low air mass (Sun vertical, at altitude, etc).

[mncharity]

Perhaps because one's world is often blue-lit? While whole-hemisphere illumination generalizes as warmer, local conditions vary. Absent direct (yellow-ish) sunlight, outdoor daylight illumination can be quite blue-ish. I've had fun recently with photos in a park under clear blue skies, shadowed by tall buildings... but with a gap, resulting in a narrow strip of bright sunlit ground. My phone will take a bit of sunlit snow as its whitepoint, and provide a blue-tinted world. Similarly for sunlit buildings in background.

[hakken306]

In space, there is only direct sunlight. On Earth, you have to consider illumination from the whole sky.

On Earth, the sun's disc at noon appears yellow-ish due to being white minus some blue light scattered away by the atmosphere. But there is also the rest of the sky illuminating the ground, as you can still easily see in shadowed areas. That is blue light from the sky hemisphere.

It very approximately adds back up to white overall for something exposed to direct sun and the whole sky, depending on the sun's position in the sky.