Photoshop Exposes Optical Illusion

One of these optical illusions came across my desk again…

optical illusion

which claims that the fields marked A and B have the same gray level. Just looking at the image it is obvious that this could not possibly be. So, normally, the untrained non-scientific mind would push it aside, maybe say, wow, really?! and wander on.

But this is where I came in – a trained scientist! And this scientist now really had enough of this and went on the quest to look for himself.

I started up trusty photoshop, zoomed into an area that contained both the fields A and B, cut a bit out of field A and dragged it next to field B …

optical illusion demonstrated

And what do you know? When the cut out little square from A is right next to field B, it is very clear that they are the same shade of gray – quod erat demimonstrum!

And we still trust our eyes? A little shadow so that the eye ‘thinks’ that the field must be brighter, makes it brighter for the eye. Could not help contemplating how many things there are that I don’t see and how many things I see that are not there.


I was really surprised that there was so much discussion about this relatively irrelevant subject, but it went even further than somebody even accusing me of cheating. Somebody made a life-action demonstration this this little optical illusion and I just have to share this here: