Illusions of color and contrast Visual illusions

Lecture

How many color shades are there, not counting white?
Four? In fact, only two - pink and green.
A few shades of green and red just seems.
Do not believe? See the same close-up picture:
Goring Grid (1870)
At the intersections of all the white stripes, except for the intersection,
on which you fix your gaze at the moment, you can see small gray spots.
Another version of the Gering grid.
Do you see small red spots at the intersection of black lines?
Illusion of flickering grid
White circles seem to blink, is not it?
Schrauf, M., Lingelbach, B., & Wist, ER (1997) The scintillating grid illusion. Vision Research, 37, 1033-1038
Achromatic contrast.
Circles have the same shade of gray.
Chromatic contrast
Surrounded by green, gray appears lilac-pink, and surrounded by red, it appears blue-greenish.
Mach Stripe (Edge Contrast)
Smooth color transition is perceived as stripes.
On the border of white, an even white line is visible, and on the border of black - an even more black line.
The cause of this illusion is lateral inhibition in the retina.
Illusion of Wertheimer-Koffka.
Part of the ring on a white background seems to be darker. If you remove the pencil, the illusion disappears.
See the chessboard with black and white cells?

Gray halves of black and white cells of the same shade.
Gray color is perceived, then as black, then as white.
Constancy of color.
Look closely at the board. She is fine?

White cells in the shade and black in the light - the same color!
However, the eyes do not notice. The brain sees black and white cells, regardless of light!
The author of the illusion is Edward Adelson (EH Adelson), 1995
The color of the figures seems to be more vivid and saturated if the figures are edged with black frames.
The background color in the part of the picture where the hieroglyphs are not outlined in white seems more saturated.
Look without looking at the cross. See green spots? But nothing green is not here.
See the blue and green spirals?
But there is nothing blue. All spirals are one shade of green (r = 0, g = 255, b = 150).
Posted by: A.Kitaoka, 2003
See the three colors (pink, lime and gray)?

And there are only two colors here. No gray here.
Gray diamonds are all the same brightness. "Dark" and "light" diamonds are not here.
Look at the center on the black dot.

Colored spots should disappear
See the light gray diagonal stripes?
If you look intently at a point in the center for a few seconds, they will disappear.
Author: Oleg Ivanov, 2006.
How many shades of green are in the picture? Two?
In fact, there is only one green shade.