• 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 illustration to take advantage of color aftereffects to see a black and white image in full color. You can use the image provided or load your own. First you will make the image black and white (gray scale), then you will stare at an image that is the inverse of the original image where all the colors are now the complementary colors. After the adaptation period the black and white image is returned. What does it look like?


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

On the Illustration tab, you can adjust the parameters and start a simulation of dark adaptation.


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

Make Image Gray: press this button to make the photograph black and white (grayscale). Then the next button will be shown.
Do Adaptation: press this button to start the adapaptation process. Keep your eye fixated on the dot in the middle of the image. The image will change of a false colored image and at the end of adaptation, it will change back to the black and white image. At the end of adaptation, the next button will be visible.
Duration (sec) set the duration of the adaptation in seconds.
Show Original: if you wish, press this button to see the original color image.
Choose a Preselected Image: Choose another image from a preselected list.
Use Your Own Image: allows you to upload your own image to simulate the Purkinje Shift.


Pressing this button restores the settings to their default values.