The same color illusion—also known as Adelson’s checker shadow illusion, checker shadow illusion and checker shadow—is an optical illusion published by Edward H. Adelson, Professor of Vision Scienceat MIT in 1995.[1] The image depicts a checkerboard with light and dark squares. The optical illusion is that the area of the image labelled A appears to be a darker color than the area of the image labelled B. However, they are actually exactly the same color.
This can be proven using the following methods[2]:
- Open the illusion in a image editing program and use the eyedropper tool – both A and B will register an RGB value of 120-120-120.
- Cut out a paper mask – by viewing the areas of the image in question without the surrounding context, the effect of the illusion is dispelled.
- Print the image and cut out the areas of the image labelled A and B – once again, viewing them out of context removes all doubt.
- Use a photometer.
