• Background
  • Instructions
  • Illustration
  • Quiz


Afterimages or aftereffects refer to visual images that are seen after the actual visual stimulus has been removed. If you stare at a bright incandescent lightbulb for even a short time and then close your eyes, you will continue to see an afterimage of that lightbulb for a relatively brief period of time. But you will notice that while the lightbulb has a yellowish hue, your afterimage will appear somewhat blue. An afterimage is actually a complementary color, which is not the same as opponent colors. Red and Green are opponent colors, but because together they also give the yellow input to the Blue/yellow system, they are not complements. So aftereffects lead to complementary colors.

Use this activity to explore color aftereffects. You can look at one or two circles to adapt to. If you use two circles, you can explore what colors are complementary colors or not. If you have two complementary colors next to each other as you adapt, the aftereffects will be as though the two colors switched places.


Full Screen Mode

To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.

Illustration Tab


Below is a list of the ways that you can alter the illustration. The settings include the following:

Start: start the adaptation. Look at the cross in the middle of the screen. One or two circles will be presented during adaptation. The screen will return to complete white when adaptation is finished. You can also start adapyation by touching or clicking the stimulus area.
Num Adapt: how many circles to adapt to: 1 or 2?
Duration (sec): how long will adaptation last, in seconds.
Color Wheels: use the color wheels to pick colors to adapt to. The color wheels change the color of the circle in the same relative position.


Pressing this button restores the settings to their default values.