Here is what appears to be a color image:
Surprisingly enough, this image is composed of only white and red light. Therefore, we might expect that we would only see white, red and pink colors in the above image. However, this is not the case. It would appear that this image contains red (tomato), brown (hamburger), green (lettuce), yellow (cheese), near white (bun), and black (background). An enlargement of this image can easily verify that this image contains only red and white light. Here is an enlargement of the area indicated by the black box above.
While the original image definitely contains more saturated colors (see below), the image with only red and white still seems to contain more than black, white, red and pink. This idea was first demonstrated by Edwin Land, the founder of Polaroid, in 1959 by using two slide projectors. Each projector had a black and white slide in it, and one projector had a red filter in front of it. Oddly enough, recent updates of psychology textbooks seem to omit any mention of this experiment.
In Land's original experiment, he took two black and white slides of the same scene. For one photograph (we'll call it slide 1) he placed a green filter in front of the camera lens. For the other photograph (slide 2) he placed a red filter in front of the camera lens. He then projected both of the slides on the same screen.
In the image above, I attempted to simulate this same concept by taking advantage of the way digital images are displayed. At the risk of insulting your intelligence, I will note that computer monitors display colors by combining varying amounts of red, green, and blue light. In fact, if you look closely at a color monitor, you should be able to see a matrix of tiny red, green, and blue lights (you may need a magnifying glass). When a color image is sent to a computer monitor to be displayed, it contains a red, a green, and a blue component. Below is the original color image that I used to generate the red/white image above.
The red, green, and blue components of this image are:
In order to generate the red/white image at the top of this page, I took the red image and made it twice as high and twice as wide. I made it twice as wide by placing an extra copy of each column next to the original column. I made it twice as wide by placing a black line between each row of the image. Pictorially, I did this:
I then took the green image and made it twice as high and twice as wide in the same way as the red image. In addition, I converted it from being green in color to grey. Pictorially, I did this:
I then created the red/white image at the top of this page by interlacing the red and white images by replacing the black rows of the red image with the white rows from the above image.
If you would like to learn more about the original experiments that Land performed, you may wish to look at the two papers he has written describing the experiments. They are:
Edwin H. Land, "Color Vision and the Natural Image: Part I," in
Proceedings of the National Academy of Sciences, Vol. 45, No. 1,
pp. 115-129, January 1959.
Edwin H. Land, "Color Vision and the Natural Image: Part II," in Proceedings of the National Academy of Sciences, Vol. 45, No. 4, pp. 636-644, April 1959.
To learn more about how it works, take a look at:
Edwin H. Land, "Experiments in Color Vision," Scientific American,
Vol. 200, No. 5, pp. 84-99, May 1959.
John J. McCann and Jeanne L. Benton, "Interaction of the Long-Wave Cones and the Rods to Produce Color Sensations," Journal of the Optical Society of America, Vol. 59, No. 1, pp 103-107, January 1969.
Edwin H. Land and John J. McCann, "Lightness and Retnix Theory," Journal of the Optical Society of America, Vol. 61, No. 1, pp 1-11, January 1971.
Edwin H. Land, "The Retinex Theory of Color Vision," Scientific American, Vol. 237, No. 6, pp. 108-128, December 1977.