Arken

I think another interesting test is if this has something to do with the way the cathode ray tube works and how our minds interpret it... does this work the same way on a printout? Anyone have a high-quality color printer and want to test it?

davidm

Yes, I get all those effects.

I suspect this also has something to do with the high-contrast, complimentary colors. Black and white are complimentary, blue and gold are nearly so. It would be interesting for somone to run this through Photoshop and replace the high-contrast colors with bland and similar ones, then repost and see if the effect is retained.

davidm

Yes, it turns out that if you replace the gold color with blue or some other dark color the effect is completely stopped. It is also stopped if you reduce the contrast by 50 percent and the brightness by 75 percent. If you reduce brightness/contrast by lesser increments, the effect is notably slowed but not completely stopped. This clearly has to do with complementary color contrasts. It is the same sort of effect you get when you see pulsating gray spots at the intersection of white bars over a black background, or the pulsating effect you get when you place spots or patches of bright red and bright green of the same tonal value next to one another.

John Page

I'm trying to remember which two colors use the same neural pathway (i.e. you can't detect the presence of both colors at the same spacetime point) and figure out if this is relevant.

John Page

Phew! Not just some defect in my central cortex, then.

Abel Stable

I printed it out (on the crummy printer at work here), and even though the size & image quality is reduced - and it's in black & white - it still has the same effect....but it doesn't hurt the eyes as bad since there are no bright colors.

davidm

What's happening is that the gold and blue are near-complementary colors. Complementary colors amplify and exaggerate each other's basic traits.

In the traditional painter's (pigment) color wheel, the three primary colors are red, blue, and yellow. They are called primary colors because they contain no color but themselves.

Complementary colors are colors on the color wheel that are opposite primary colors. They contain 50:50 mixes of the two other primaries. The complement of red is green: Green contains a 50:50 mix of the two other primaries, blue and yellow.

The complement of blue is orange: Orange contains a 50:50 mix of red and yellow.

The complement of yellow is violet: violet contains a 50:50 mix of red and blue.

When you mix complementary colors together 50:50, you get gray.

It has long been known that when you place complementary colors next to or near each other, strange effects take place.

Red and green side by side amplify each other's saturation/intensity contrast

Blue and orange side by side amplify each other's warm/cool contrast. Blue recedes sharply, orange springs forward.

Yellow and violet amplify each other's dark/light contrast. Yellow appears lighter than normal, violet darker than normal.

In the case of the moving spirals, blue and gold/orange, near complementaries, are competing for the attention of the eye's cones. They are amplifying each other's vividness. The brain is rapidly shuttling back and forth between them, creating an illusion of movement. Imagine you are a teacher in a classroom full of bawling blue and gold children. Your neck will swivel from side to side trying to pay attention to them. Eventually you will get dizzy and the room will seem to swim.

The illusion is undoubtedly amplifed by the sprial forms, which themselves suggest movement to the brain.

But notice that when you stare fixedly at any point in this piece of art, the illusion vanishes after a few moments. This is because cones, which deal with color, are concentrated in the center of the retina. When you stare fixedly at any point, the cones focus on that color alone, and are not distracted by the others blue-gold contrasts. Rods, which deal with light-dark contrasts, are spread across the retina. This is why stars frequently look brighter in your peripheral vision: The light is more evident and color does not compete with it.

Jesse

The primary and complementary colors are a little different for light, though. There, the three primary colors are red, blue, and green; the secondary colors are magenta, cyan and yellow; and the complementary colors are red + cyan, green + magenta, and blue + yellow. There's an interactive demo of how the primary colors of light mix here. Since these primary colors are based on the three different photoreceptors of your eyes, I believe these complements would actually be more striking visually (and I think the afterimage of green would be magenta, the afterimage of yellow would be blue, and the afterimage of red would be cyan, but I'm not absolutely sure).

Also, on my monitor the colors of the spirals are not blue and gold but blue and a light greenish color...what do other people see?

Arken

Wow. Okay, thanks.

Per

Another pretty cool illusion. This one doesn't move around though.