Optical illusions are often fanciful diversions that keep us keen to the fact that our own minds can not only be tricked, but often tricks itself. Some illusions are so mind-blowing that we try with all of our mental capacities to see reality, but we struggle to convince our minds that what we’re seeing isn’t actually what it appears to be.
One of our favorites is the shaded shield illusion. Thanks to a phenomenon known as brightness constancy, we look at the shield above and assume that the area being pointed to by the green arrow is a lighter shade of grey than the area being pointed to by the blue arrow. In reality, they are the same shade, but our mind “knows” that the alternating light and dark rings within the shield should not be overpowered (or equaled) by the shading effect from the light source.
In fact, they are. The shadowed light ring area is the same shade of grey as the unshaded dark ring area. Pull this into Photoshop and check it out for yourself.