Grey square illusion

[SamKR]

In this image do you think the the squares A and B are of different shades of grey (is the square B is lighter than the square A) ?
Or, are A and B of the same shade?

[Babadhari]

well i put my thumb between them and they appear to be the same shade.
like most things , the apparrent difference between them is an illusion

[SamKR]

Also, see this animation: http://en.wikipedia.org/wiki/File:Optic ... quares.gif

[Babadhari]

the original one i saw had two grey cubes stacked upon each other,

[kmath]

Wow that is insane!

[purple planet]

cool stuff

[daverupa]

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.

source

[SamKR]

In this image do you think the the squares A and B are of different shades of grey (is the square B is lighter than the square A) ?
Or, are A and B of the same shade?

In my opinion the square A and B have different shades in the image (of the first post). My question to those who think they are of the same shade, why do you think that is the case?

[kmath]

In this image do you think the the squares A and B are of different shades of grey (is the square B is lighter than the square A) ?
Or, are A and B of the same shade?

In my opinion the square A and B have different shades in the image (of the first post). My question to those who think they are of the same shade, why do you think that is the case?

They are the same shade. Cover up all the other squares and you'll see.

[SamKR]

Why does the illusion work?
...
source

In my opinion the square A and B have different shades in the image (of the first post). My question to those who think they are of the same shade, why do you think that is the case?

They are the same shade. Cover up all the other squares and you'll see.

I think that to say the squares are of the same shade (as an objective reality), is a bigger and more significant illusion.
And, why does this bigger illusion work? Because of not giving attention to the things as they really are (or as they arise, or as they are experienced) but to give attention to a conceived "objective reality". I wonder if you agree.

[kmath]

I think that to say the squares are of the same shade (as an objective reality), is a bigger and more significant illusion. And, why does this bigger illusion work? Because of not giving attention to the things as they really are but to give attention to a conceived "objective reality". I wonder if you agree.

I disagree completely. You are not giving attention to things as they are in this case. You're giving attention to things as they seem. With a bit of investigation, you see things as they are.

[kmath]

I think that to say the squares are of the same shade (as an objective reality), is a bigger and more significant illusion. And, why does this bigger illusion work? Because of not giving attention to the things as they really are but to give attention to a conceived "objective reality". I wonder if you agree.

I disagree completely. You are not giving attention to things as they are in this case. You're giving attention to things as they seem. With a bit of investigation, you see things as they are.

[SamKR]

I think that to say the squares are of the same shade (as an objective reality), is a bigger and more significant illusion. And, why does this bigger illusion work? Because of not giving attention to the things as they really are but to give attention to a conceived "objective reality". I wonder if you agree.

I disagree completely. You are not giving attention to things as they are in this case. You're giving attention to things as they seem. With a bit of investigation, you see things as they are.

What kind of investigation would change the vivid experience of seeing different shades to anything else? How the things really could be other than the direct experience?

[Mkoll]

For more visual trickery, see this TED talk by Beau Lotto:

http://www.youtube.com/watch?v=mf5otGNbkuc

PS

I don't think arguing about this gets anywhere but to a mind of ill will and delusion...

[SDC]

Madness!!!!!

[binocular]

Also, see this animation: http://en.wikipedia.org/wiki/File:Optic ... quares.gif

Well duh. To me, they start off the same, and end up different.

They are the same shade. Cover up all the other squares and you'll see.

Covered up the rest, still don't look the same.

I think that to say the squares are of the same shade (as an objective reality), is a bigger and more significant illusion.
And, why does this bigger illusion work? Because of not giving attention to the things as they really are (or as they arise, or as they are experienced) but to give attention to a conceived "objective reality". I wonder if you agree.

Agreed.
Color is not an inherent property of an object, but a contextual one, depending on other objects in its proximity and the kind of light we view them in.

[kmath]

I think that to say the squares are of the same shade (as an objective reality), is a bigger and more significant illusion. And, why does this bigger illusion work? Because of not giving attention to the things as they really are but to give attention to a conceived "objective reality". I wonder if you agree.

I disagree completely. You are not giving attention to things as they are in this case. You're giving attention to things as they seem. With a bit of investigation, you see things as they are.

What kind of investigation would change the vivid experience of seeing different shades to anything else? How the things really could be other than the direct experience?

By investigation, I meant covering up the other squares.

If things couldn't be other than the direct experience, this deal wouldn't be much of an illusion.

[Kim OHara]

A question for everyone, but especially for those disagreeing with each other:
Where is your "experience" located?
Is it ...
(1) the real colour of the real tiles and cylinder (assuming they existed in the real world) ?
(2) the real colour of the tiles in the picture?
(3) the perceived colour of the tiles in the picture?
(4) the interpreted colour of the tiles in the picture (as per Dave's excellent post)?


Kim

[SamKR]

What kind of investigation would change the vivid experience of seeing different shades to anything else? How the things really could be other than the direct experience?

By investigation, I meant covering up the other squares.

By covering up the other squares you are changing the conditions upon which the shades of the squares depend - so, that is not a mere investigation.

If things couldn't be other than the direct experience, this deal wouldn't be much of an illusion.

When you don't look at the squares A and B, are there the shades of grey objectively lying out there (on those squares)?

[SamKR]

A question for everyone, but especially for those disagreeing with each other:
Where is your "experience" located?
Is it ...
(1) the real colour of the real tiles and cylinder (assuming they existed in the real world) ?
(2) the real colour of the tiles in the picture?
(3) the perceived colour of the tiles in the picture?
(4) the interpreted colour of the tiles in the picture (as per Dave's excellent post)?


Kim

Hi Kim, I would say that "experience" is the direct perception of shades (so, I choose (3)). And, strictly speaking, experiences are not located anywhere. It is because the idea of location (here and there) itself is constructed due to avijja-based experiences, and therefore location is not primary than the experience itself. Experiences do not happen in locations, rather locations happen in experiences.