Colour is Weird (Part 3)

I’ve been saving the best colour weirdness for last. The seeing of colours that aren’t even there (a little-known phenomenon discovered by Edwin Land, the inventor of the Polaroid camera). Imagine you are taking pictures of a colourful scene, but using black and white film (or the B&W setting on your phone). We’re going to take two pictures of the colourful scene, taken from exactly the same position. We’ll call the first picture the “grey” picture. However, for the second picture we will put a transparent red filter in front of the camera, so that it only gets to see the world in shades of pink and red. We’ll call it the “pink” picture. But remember, is still records only a black and white image. The grey shades will probably be different between the two pictures. For example, if the scene were three balls (red, white, and blue) the two pictures might look like this:

Now, let’s project these pictures onto a screen together using two separate computers and LCD projectors. We will adjust the two projectors so that the images overlap perfectly. And one other adjustment: in front of the “pink” projector we will again put the transparent red filter, so that the projected image on the screen is returned back to the shades of pink and red that were originally seen by the camera. What do you think you’d see on the screen? One projector is showing shades of grey, and the other is showing pinks. There is, for example, no blue or yellow being projected anywhere. But on the screen these other colours can be clearly seen! Live demonstrations of this effect have actually caused some people to fall out of their seats, it’s so weird.

Don’t believe me? Well, it’s a lot of trouble to set up the projection to demonstrate this. But it’s totally worth it if you ever get the chance. There is one somewhat lame way of roughly simulating the effect for you now. The hard part is projecting two separate images using a single computer screen. The lame workaround is to interlace the images, alternating a thin horizontal strip of one image, then a strip of the other, and so on. Viewed at a distance from the computer screen, you can roughly experience what it’s like to see both images, overlapped. The effect is not nearly so powerful, but you’ll still get to roughly have the experience of seeing colours that aren’t there anymore. Here’s how it’s done (using the great Wendy Carlos photos):

And what happens when you view grey and pink together? Seriously weird appearances of green, yellow, and light blue:

This interlaced version is only a pale approximation of the full effect with two projectors, and yet it does suggest the effect of seeing colours that you know just aren't there. The perception of colour is the weirdest thing evar.