Adelson's Checkershadow Illusion

Squares A and B are the same shade of grey.

Credit:

Checkershadow Illusion copyrighted by Edward H. Adelson

Proof:


zoom in and see the colors of the squares.  They are both the same color.  Here is Edward Adelson's proof and an explanation. 

• Below: the colored regions appear rather different, roughly orange and brown. In fact they are the same colour, and in identical immediate surrounds, but the brain changes its assumption about colour due to the global interpretation of the surrounding image. 
• Also, the white tiles that are shadowed are the same color as the grey tiles outside of the shadow.