The controversy caused by a skirt: platinum or blue black?

One picture can split the Internet into two camps of mutual attacks - admit it, this is a common thing for the Internet. However, in the past half day, people on the whole social network have been discussing whether this perfectly normal slim lace dress is blue and black or white and gold. The two camps are at odds with each other. But this debate is not only about social media, but also about primate biology, and how human eyes and brain have evolved to be suitable for seeing things in a sunny world.

Light enters the eye through the lens, and different wavelengths of light correspond to different colors. Light strikes the retina at the back of the eyeball. Pigment senses light and sends signals to the visual center through neural connections where the brain processes these signals into images. Although strictly speaking, the light is reflected from the object, which is limited by the wavelength composition of the light source, you should not worry that your brain will automatically recognize the original color of the light emitted, and cut the color from the "real" color of the object. "Our visual system will give up the information about the light source and extract the information about the reflected light." Jay Neitz, a neuroscientist at the University of Washington, said, "I have studied the individual differences of color vision for 30 years, and this dress is one of the largest cases of individual differences I have seen." (What Neitz sees is white and gold.)

The original photo (middle) and white gold (left) or blue black (right) after different white balance adjustments.

Normally, this system works well. However, this photo touches the edge of the senses. This may be because the human brain is encoded in this way. The human eye has evolved to be able to see things clearly in sunlight, but the color of sunlight will change, ranging from pink at dawn to blue and white at noon, and then back to pink at dusk. Bevil Conway, a neuroscientist who studies color and vision at Wellesley College, said: "When you see this picture, your brain is correcting this color difference according to sunlight. So if people think the light source is blue and ignore the blue part, they see white and gold; If they ignore the gold, they see blue and black. " (However, Conway himself somehow sees blue and orange.)

We asked our excellent picture design team to process this picture a little on Photoshop and give the RGB values of some color patches on the picture. We think this picture can definitely answer the question "What color is the skirt?" - the results are really close.

Taking the image version on Buzzfeed as an example, PS in this version said that the blue people see is really blue, but this is probably because of the background, rather than its true color. "Look at the place where your RGB value is equal to R93, G76, B50. If you just look at these numbers and ask you to say what color it is, what would you say?" Conway asked.

Er... a little orange?

"Yes," Conway said. "But our PS played a bad trick - taking white as the background, and it looked black. If I put this color on a neutral black background, I bet it will appear orange." He also tried these words on Photoshop, and he thought that the color of the skirt should be blue and orange.

The point is that your brain tries to push ambient light out of the picture, and then judge the color of the skirt. Even though I didn't know how to see the white and gold Neizi, I also admitted that the skirt was probably blue in fact. He said: "I also printed out the photos. Then I cut a small part and looked carefully. After excluding the environment color completely, the color of the skirt is between the two, rather than this dark blue. My brain believes that blue comes from external light sources. Others believe that blue is the color of the skirt itself."

WIRED's own photo editing team was once in despair of temporary existence because too many people saw White&Gold, but they finally accepted the explanation of color constancy determined by the environment. Neil Harris, our senior photo editor, said: "When I adjusted the white balance of this picture based on this idea, I found that it could not be adjusted well." The blue he saw in the highlight told him that the white he saw was actually blue, while the gold was actually black. When he reacts, adjust the white balance with the darkest pixel in the picture, and the skirt will become blue and black. "When things are clear, the proper point to adjust the white balance of this picture is the darkness," Harris said.

When the environment changes, human visual perception will also change accordingly. Kang Wei said, "Most people think that the blue on the white background is blue, but some people may regard the blue on the black background as white." He even half jokingly put forward a guess: since the white gold visual deviation can explain the color of the skirt seen in strong sunlight, Then "I think night owls are more likely to think the skirt is blue and black".

At least, we can reach an agreement on one issue: the person who thinks the skirt picture is white is absolutely wrong.

Rewards&Benefits