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Comment by qiqing | Hacker News Reader

It's the color of incandescent bulbs, fire, and other popular sources of light, reflected off of a large variety of surfaces.

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This wouldn't explain why the same effect was seen from photos of graffiti (which presumably were outside, in the day.)

"When someone told him that it was probably due to the colors of flesh in photographs, he tried it with a pool of graffiti. Still orange. "

I'm curious how much exposed wall was included in those pictures. Graffiti is vastly more common on brick and concrete surfaces, which 99% of the tie are red, yellow, cream, or gray. Regardless of what color the graffiti is, if there's a lot of backdrop behind it I'm not at all surprised that it'd average to orange.

Pick something else like "pictures of forests" instead of "pictures of graffiti" and suddenly your average stops being orange because you're not taking photos of buildings anymore.

It is perhaps worth pointing out that I observed the same effect in collections of purely synthetic art (such as Fractals).

https://www.flickr.com/photos/krazydad/3794489938/in/set-721...

While I don't think this rules out light as a possible culprit, it perhaps implies that humans are mimicking the natural world when they are making color choices.

This is pretty much what I was coming here to say.

Don't forget that we live under a yellow sun, too. There is a hell of a lot of warm light in our world, natural and artificial.

Sun is actually white... which is why you see a all the colors in a rainbow. I know Superman lied to you. :)

Sun's radiation peak energy at sea level is around 500-600nm http://en.wikipedia.org/wiki/Sunlight#mediaviewer/File:Solar...

which is green

http://en.wikipedia.org/wiki/Light#mediaviewer/File:Linear_v...

That is why grass/trees are green - they consume only the edges of the spectrum (about 10-15% of the total sunlight coming through) bouncing the rest back.

With respect to the original point about orange being average color of Internet photos - keep in mind that most photos are produced by digital CCD cameras which are more sensitive to orange/red than green/blue.

http://www.gitthailand.com/image/ccd-spectrum.jpg

Interesting. I guess it actually emits all sorts of frequencies of light visible or not, but Superman is still wrong. :)

Why does that explain why plants are generally green? If you had told me that the energy peak was at X wavelength, I would have guessed that plants absorbed most of that wavelength in order to not be wasteful rather than preferentially reflecting that wavelength.

>If you had told me that the energy peak was at X wavelength, I would have guessed that plants absorbed most of that wavelength in order to not be wasteful rather than preferentially reflecting that wavelength.

the plants consume edges of spectrum, so they would bounce the X wavelengths (green in case of our Earth) as it is just an unnecessary heat for them.

Plants are actually pretty miserably inefficient at turning sunlight into stored energy: http://en.wikipedia.org/wiki/Photosynthetic_efficiency (not only do they reflect away most of the light, but photosynthesis isn't linear at all graphed against light intensity: most of the noonday sun is wasted)

There's no real consensus on why. (There's some wild guessing that green photons might be too hot to handle: smashing fragile biomolecules apart rather than powering them... (http://scienceline.ucsb.edu/getkey.php?key=500) but then why does chlorophyll run fine on purple light?) You'd figure that there would be incredible selection pressure on increasing photosynthesis efficiency, but maybe they're stuck on a local maxima: it's not like a single mutation can turn a C3 plant into a C4 plant: http://en.wikipedia.org/wiki/C4_photosynthesis

Exactly. The simplest explanation in my mind is that it's a white balance issue. Most photos are taken in some form of daylight, which is generally in the orange range without a pure white on a "correct" exposure. On average, photos will be taken in warmer (orange) rather than colder (blue) tones.

It would probably even work on a bunch of photos taken of a white wall in some natural light, if you averaged them out. More of an orange hue than pure white, certainly.

So the color could change in the next years with the emergence of fluorescent lamps, LEDs and cold cathode lighting.

Don't most of those newer lighting technologies usually try to imitate the color temperature of traditional lighting?

Compact fluorescent bulbs (cheap ones anyway) are quite "warm" and LEDs are cool, almost blue. I ended up combining them in my kitchen to get a color I liked.

That's what I thought of too. It could be tested by averaging a pool of images lit by fluorescent bulbs, LEDs, or LCD monitor glow.

Also the colour of a human, the most photographed animal on the planet.

The article addresses that and intentionally chooses non-human subjects such as walls of graffiti. These still show his `emergent orange' effect.

At first I assumed it was his averaging technique, but I'm more apt to believe it has to do with the spectrum of light which is being `sampled' by the selection of photos.

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