Nell Greenfieldboyce, an NPR science correspondent, has an interesting article in one of the National Public Radio blogs. We should see it for its cautionary value to us when we look at the shroud.
“These X’s Are The Same Shade, So What Does That Say About Color?,” she proclaims in the title. They are:
Nell goes on to write:
Mark Fairchild, who studies color and vision science at the Rochester Institute of Technology, says that even physicists get it wrong when they confidently assert that color is just a wavelength of light.
"My usual quick answer to that is I can take any wavelength and make it appear almost any color," says Fairchild.
That’s because color is not something out there in the world, separate from us.
"The agreed-upon technical definition of color," says Fairchild, "is that it’s a visual perception."
So don’t try to tell Fairchild an apple is red. He’ll say, no it’s not, technically — red is just your perception.
"I could change the color of illumination on that apple and make it look green or blue or something completely different," he says. "The redness isn’t a property of the apple. It’s a property of the apple in combination with a particular lighting that’s on it and a particular observer looking at it."
All three of those elements are critical to the idea of "red" or any other color, he says. "You have to have somebody looking at that in order to combine all that information and produce a perception."
Fairchild likes to tell this story:
One night, when his daughter was young, he and his wife decided to have dinner by candlelight. They fed their daughter first, and his wife served macaroni and cheese.
The table was set, the candles were lit. But his daughter took one look and recoiled from her food’s color.
"She started almost crying and getting very upset and yelling at us because we gave her the white macaroni and cheese and not the yellow macaroni and cheese," says Fairchild. "Her favorite is the yellow macaroni and cheese."
Because he studies color perception, Fairchild immediately realized what was going on.
"I said ‘Hold on, stay right there. I can magically turn it into yellow macaroni and cheese,’ " he recalls, "and I walked across the room and I flipped on the lights."
The mac and cheese in her bowl, it turned out was, indeed, yellow. But when it was only illuminated by the candlelight, which is very yellow, the light reflecting off her food had looked almost identical to the light reflecting off the white bowl.
"She just responded to what her eyes created there, the perception her eyes created," Fairchild says. "She thought it was white because it matched the bowl."