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Color Constrast

Images without overlays
Images without the overlays. The colors look different.
Images with overlays
Images with the overlays. The colors are the same.
A cube, with 25 colored squares on each side in a five by five grid.
The middle square on the top face and the middle square on the side face look like they are different colors.
Two orange horses on a background that fades from light orange to dark orange.
The horses look like they are different shades of orange.
A cylinder casts a shadow over a checkerboard surface.
Two of the squares in the checkerboard are the same shade of gray.
View of a cube head-on, with the horizon aligned with the shared edge of the two visible sides.
The two faces of the cube look like they are different shades of gray.
An array of pink, green and gray squares on a background that is half pink and half green.
What color are the squares?

You see an image where there are two regions that look like the color is different.

When you overlay a mask that blocks out other parts of the image except those two regions, you can see that the color is the same.

Background

Our brain interprets the information that comes from our eyes, so color perception is subjective and depends on context. For example, if your brain understands that part of an image is in shadow, you will interpret colors in the shadowed region differently than in a lit region. Sometimes the contrast of surrounding colors changes your perception of a color.

This type of optical illusion can happen when people put on makeup, to make their eye color look brighter or darker, or a slightly different shade. Sometimes the color of a person's clothes can also change the apparent color of their eyes.

Materials

  • these image files
  • cardstock (optional)
  • a color printer
  • scissors, or a utility knife and a metal ruler
  • 5 mil lamination sheets, and a laminator (optional)

Construction Instructions

Download the image files, and print some or all of them using a color printer. (You can use black and white for the masks.)

Carefully cut out the windows in each mask. Young kids should use scissors. Adults or older kids can get cleaner results using a utility knife and a metal ruler

You can use regular paper for your images. But, if you want your exhibit to last, print the images on cardstock, and laminate them (after cutting the windows).