The Crayon Project

Thoughts and Observations
28
April 2015

Your Brain and the Checker Shadow Illusion #theCrayonProject

There’s a video embedded below. You can watch it before you read this, or you can read this before you watch it. Either way, what you see will still leave you a little dazed as to how that just happened, right in front of your eyes? Well not right in front of your eyes, more like just after your eyes took in the information and your brain started messing with it 🙂

Here’s the explanation from Wikipedia. I chose them over the MIT explanation (where the illusion was published in 1995) because it was easier to understand. Really 🙂

The visual system needs to determine the colour of objects in the world. In this case the problem is to determine the gray shade of the checks on the floor. Just measuring the light coming from a surface (the luminance) is not enough: a cast shadow will dim a surface, so that a white surface in shadow may be reflecting less light than a black surface in full light. The visual system uses several tricks to determine where the shadows are and how to compensate for them, in order to determine the shade of gray “paint” that belongs to the surface.

The first trick is based on local contrast. In shadow or not, a check that is lighter than its neighboring checks is probably lighter than average, and vice versa. In the figure, the light check in shadow is surrounded by darker checks. Thus, even though the check is physically dark, it is light when compared to its neighbors. The dark checks outside the shadow, conversely, are surrounded by lighter checks, so they look dark by comparison.

My interpretation goes something like this…. your brain messes with information from time to time. Mostly, I understand, because it’s underpowered and frankly, a little lazy. So we don’t always see what we’re looking at. Well not accurately, anyway. In my journey of #theCrayonProject I’ve become fascinated by those places and spaces where what we think is real is not actually real at all. It’s important both to acknowledge that those spaces exist, and to practice identifying them. Not doing that may leave you horribly exposed.

 

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