by Tekija » Tue Dec 19, 2023 8:24 pm
Chris Peterson wrote: ↑Tue Dec 19, 2023 4:49 pm
Lasse H wrote: ↑Tue Dec 19, 2023 4:44 pm
JeffW wrote: ↑Mon Dec 18, 2023 3:07 pm
Sorry but they don't look the same color to me, with or without the bridge. Not even close, one is definitely lighter, one darker.
But that's the whole point of an optic illusion ! - In this case: that they "don't look the same color", but yet they are.
If you measure the color in the two squares, you will find that they both are RGB(120, 120, 120).
And the reason is because of the way our brain compensates for shadows. We interpret the chessboard as having squares with only two colors, uninfluenced by shading.
Indeed. Here's how the creator of the illusion explained it:
"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."
[quote="Chris Peterson" post_id=335757 time=1703004553 user_id=117706]
[quote="Lasse H" post_id=335756 time=1703004250 user_id=123973]
[quote=JeffW post_id=335708 time=1702912027]
Sorry but they don't look the same color to me, with or without the bridge. Not even close, one is definitely lighter, one darker.
[/quote]
But that's the whole point of an optic illusion ! - In this case: that they "don't look the same color", but yet they are.
If you measure the color in the two squares, you will find that they both are RGB(120, 120, 120).
[/quote]
And the reason is because of the way our brain compensates for shadows. We interpret the chessboard as having squares with only two colors, uninfluenced by shading.
[/quote]
Indeed. Here's how the creator of the illusion explained it:
"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."