Ever since I was a freethinking and precocious kid, I have loved optical illusions. Not so much the ones where the answer always is "They are both the same length," but more ones that really fool the eye. Like the fantastic architecture of M.C. Escher drawings and the "Magic Eye" deep-vision images.
I stumbled across this diagram and the caption "The squares marked A and B are the same shade of gray." Take a look. No way, right?
Way. I opened this image in Photoshop, and used the clone stamp to brush the color of A over to B. Indeed, they are both the exact same shade of gray!
13 comments:
because of the shadow or what?
The shadow must have something to do with it. But how? That's what makes this so fascinating! I can't figure out why it fools the eye so well. Maybe "only the shadow knows ..."
You're a pistol, free... I did the same thing in photoshop with this image a few weeks ago. Freaky deaky!
you ever read any C.S. Lewis freethinker?
C.S. Lewis ... wasn't he the writer who thought the earth is only 6000 years old and that humanity began with Adam and Eve?
Have you read any Richard Dawkins, Mikey?
Hey... if your really blur your vision while looking at it, A & B quickly become the same shade again.
Just another way to burn a few seconds :)
yes he was free, but not before he had the same perspective you are coming from. His earlier works reflect it too. Even if you don't come to be a Christian, I challenged you to examine his journey intently. It would at least enlighten your free-thinking journey. I have an open mind and am open to friendly debate. I would hope that you would have an open mind too instead shrugging me off as a "bible thumper." I mean no ill feelings towards you on any level so please do not take offense that, in the name of Jesus Christ, I will be praying for you.
Mikey, no offense intended by calling you a "bible thumper." I know many Christians who proudly use this term.
Tell you what -- I'll check out C.S. Lewis if you check out Richard Dawkins, deal?
deal
Allow me to explain this optical illusion ...
Click here to see the original image and two stripes of the same shade.
By joining the squares marked A and B with two vertical stripes of the same shade of gray, it becomes apparent that both squares are the same.
Why does the illusion work?
The visual system needs to determine the color 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.
A second trick is based on the fact that shadows often have soft edges, while paint boundaries (like the checks) often have sharp edges. The visual system tends to ignore gradual changes in light level, so that it can determine the color of the surfaces without being misled by shadows. In this figure, the shadow looks like a shadow, both because it is fuzzy and because the shadow casting object is visible.
The "paintness" of the checks is aided by the form of the "X-junctions" formed by 4 abutting checks. This type of junction is usually a signal that all the edges should be interpreted as changes in surface color rather than in terms of shadows or lighting.
As with many so-called illusions, this effect really demonstrates the success rather than the failure of the visual system. The visual system is not very good at being a physical light meter, but that is not its purpose. The important task is to break the image information down into meaningful components, and thereby perceive the nature of the objects in view.
Yeah, what he said.
Oh!
It's all perfectly clear to me now ... NOT!
Anyway, thank you for the dissertation, Ed!
Once you can accept the universe as matter expanding into nothing that is something, wearing stripes with plaid comes easy. - Albert Einstein
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