Best Illusion Ever

"Today there is no dark or light
Today there is no black or white
Only shades of gray."
- The Monkees

I've posted illusions before, but this is the most amazing one I've even seen! No matter how I try, I cannot see squares A and B as the same shade of gray. But they really are. To prove it, cut holes in a piece of paper and cover all the squares but those - or else print out the picture and cut out those two squares. You won't believe your eyes!

Additional Note: For those who are still skeptical, see below!