Optical Illusion
An interesting optical illusion that arrived in my mailbox one morning:
After attending part of a course of lectures on Systems Engineering where colour has become a major subject area, I started to think about this image. If the eye sees colour and intensity as two different quantities, then it must know how to differentiate between different intensities. Take a look the the picture below, though. If you don't believe that A and B are the same colour (and shade of that colour), check it for yourself. It's quite impressive.
Thanks to Xevian, the original page has been located, which has amongst other things an explanation of why this happens.