Recently I was eating a yellow rice for lunch in a restaurant with only yellow lights. But the rice looked white! I was intrigued by this because I always thought it should look yellow since the yellow pigment reflects only yellow light, but the rice looked really, really white. Why is that?
I thought it could be something about the rice, but any yellow object was looking white. The room was full of yellow light bulbs (not normal yellowish bulbs, but very tinted yellow lights) and there was no other color of light to interfere. Maybe there's something to do with human perception?
[Physics] Why does a yellow object turn white under a yellow light? Shouldn’t it turn yellow instead
absorptionperceptionreflectionvisible-lightvision
Best Answer
Your brain adjusts your perception of color to compensate for lighting that is strongly tinted. This was the reason for the violent conflict some time back about a certain dress. Depending on whether people perceived the dress was being lit by yellow-tinted or blue-tinted light, they saw either a black and blue dress or a white and gold dress. Here's an animated version to show that color happens in the brain, not physics.
Here's another picture to show that your brain interprets colors contextually. The squares marked A and B are exactly the same shade of grey. But, because your brain interprets square B as being in a shadow, it "knows" that the "real" color of the square is lighter. So, you perceive a lighter shade than what is actually there.
Below is an edited version of the checkerboard showing a single color linking the squares A and B (the squares A and B have not been recolored). What I find funny is that half the time I see the squares and line as single color, and half the time I see a gradient from the "dark" square to the "light" square. In the animated picture above, I still see the moving swatch fading from one color to another as it moves.
So, because of the strong yellow lighting in the restaurant, your brain thought the yellow of the rice was due to the lighting and "corrected" your perception. I keep saying the brain does this because all of this visual post-processing happens subconsciously.
Pictures taken from the wikipedia article: https://en.wikipedia.org/wiki/Checker_shadow_illusion
To summarize, the physics of light ends at your retina. Particles of light (photons), each with a a certain energy, hit the cells of your retina, setting off electrical signals that travel to your brain. Your brain then processes these electrical signals to create a coherent image. These processes include factors from memory (what things "should" look like), local contrasts (in color and brightness), cues from the environment (including available light sources), and many others. The result of all this mental post-processing can result in identical photons creating different colors in the mind, as evidenced by the picture above.
Now, who do you trust? Me or your lying eyes?