Optical illusion

October 20th, 2002

i was just browsing another forum and found this:

Belive me, it works if you print out the picture, cut out the 2 squares and place them side by side they are the same

October 20th, 2002

never would've thought

**SPeedY_B** · October 21st, 2002

That's just damned freaky.
I think the confusion comes from the letter colouring. As grey is a neutral colour you are confused by the lighter and darker colouring of the letters. I love pics like this
NEXT...!

October 21st, 2002

wait so do those squares thing works or not?

**Khayman** · October 21st, 2002

how it works

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.

October 21st, 2002

ummm .... you lost me there Khayman

**Glaanieboy** · October 21st, 2002

When I printed it out it did work, but see what happened when I edited it a little in Paint Shop Pro:

Strange right? Here the colors are not the same. It might be explained in Khayman's post, but just like mafia, I lost him.

[edit]Uhm.. oops, looks like I edited the pic a little wrong, now it looks like the trick doesn't work, but better editing let me see otherwise. Sorry, just ignore this post. Here is the newly edited pic:

[/edit]

October 21st, 2002

well now it does look ok

**Khayman** · October 21st, 2002

all you need to do is use a paint dropper in psp or ps to "pickup" the colours and you will see they have the same RGB value

October 21st, 2002

Originally posted by Khayman
how it works

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.

wtf :confused:

**SPeedY_B** · October 21st, 2002

i think summed up it means ...
"they're the same colour, they dont look it, its freaky"

October 21st, 2002

Originally posted by SPeedY_B
i think summed up it means ...
"they're the same colour, they dont look it, its freaky"

oh ok,much better explanation

October 20th, 2002	Top \| #1
pothitos Unregistered Posts: n/a	Optical illusion i was just browsing another forum and found this: Belive me, it works if you print out the picture, cut out the 2 squares and place them side by side they are the same

October 21st, 2002	Top \| #3
SPeedY_B I may actually be insane. Joined: March 2002 Location: Midlands, England Posts: 15,800 Reputation: 2877 Power: 310	That's just damned freaky. I think the confusion comes from the letter colouring. As grey is a neutral colour you are confused by the lighter and darker colouring of the letters. I love pics like this NEXT...! 1. SPeedYB.co.uk 2. CamPortal.co.uk 3. MacIRC.co.uk

October 21st, 2002	Top \| #5
Khayman I'm sorry Hal... Joined: January 2002 Location: England Posts: 5,514 Reputation: 1210 Power: 194	how it works 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. "I'm on the server side. I don't know what side you're on"

October 21st, 2002	Top \| #9
Khayman I'm sorry Hal... Joined: January 2002 Location: England Posts: 5,514 Reputation: 1210 Power: 194	all you need to do is use a paint dropper in psp or ps to "pickup" the colours and you will see they have the same RGB value "I'm on the server side. I don't know what side you're on"

October 21st, 2002	Top \| #10
pothitos Unregistered Posts: n/a	Originally posted by Khayman how it works 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. wtf :confused:

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October 20th, 2002	Top \| #2
mafiafromrussia Unregistered Posts: n/a	never would've thought

October 21st, 2002	Top \| #4
mafiafromrussia Unregistered Posts: n/a	wait so do those squares thing works or not?

October 21st, 2002	Top \| #6
mafiafromrussia Unregistered Posts: n/a	ummm .... you lost me there Khayman

October 21st, 2002	Top \| #7
Glaanieboy OSNN Veteran Addict Joined: March 2002 Location: The Netherlands Posts: 2,626 Reputation: 270 Power: 153	When I printed it out it did work, but see what happened when I edited it a little in Paint Shop Pro: Strange right? Here the colors are not the same. It might be explained in Khayman's post, but just like mafia, I lost him. [edit]Uhm.. oops, looks like I edited the pic a little wrong, now it looks like the trick doesn't work, but better editing let me see otherwise. Sorry, just ignore this post. Here is the newly edited pic: [/edit]

October 21st, 2002	Top \| #8
mafiafromrussia Unregistered Posts: n/a	well now it does look ok

October 21st, 2002	Top \| #11
SPeedY_B I may actually be insane. Joined: March 2002 Location: Midlands, England Posts: 15,800 Reputation: 2877 Power: 310	i think summed up it means ... "they're the same colour, they dont look it, its freaky" 1. SPeedYB.co.uk 2. CamPortal.co.uk 3. MacIRC.co.uk

October 21st, 2002	Top \| #12
mafiafromrussia Unregistered Posts: n/a	Originally posted by SPeedY_B i think summed up it means ... "they're the same colour, they dont look it, its freaky" oh ok,much better explanation

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