optical illusion

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Abdul Alhazred
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Re: optical illusion

Post by Abdul Alhazred » Mon Oct 15, 2018 2:25 pm

I perceive only 3 colors.

Does that mean I'm color blind? :coolspecs:
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Re: optical illusion

Post by ceptimus » Mon Oct 15, 2018 2:43 pm

Most people see the left arm of the Y looking more green and the right arm looking more blue.

How about this one? This also only has three colours, not counting the single black pixel right at the centre.

Image

The 'Y' version again, seeing as how we're on a new page

Image

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Witness
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Re: optical illusion

Post by Witness » Tue Oct 23, 2018 1:51 am

ceptimus wrote:
Mon Oct 15, 2018 2:43 pm
...
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Re: optical illusion

Post by gnome » Tue Oct 23, 2018 12:55 pm

It's no surprise... Band colors together and it will seem like a sort of blend. In this case two different blends.

RGB screens had only three colors too.
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Re: optical illusion

Post by ceptimus » Wed Oct 24, 2018 4:29 pm

gnome wrote:
Tue Oct 23, 2018 12:55 pm
RGB screens had only three colors too.
Not sure what you mean by RBG screens. If you're referring to the usual sorts of displays used on TVs and computer monitors, then yes, there are usually only three types of phosphor - but usually the intensity of each red, green, or blue phosphor dot can be specified with 5, 6, 8, or more bits of resolution - so these displays can show tens of thousands, up to millions of different colors.

This is different to the optical illusions that really do use only three colors over large areas (many pixels) - and with no variation of intensity of those colors. You could reproduce the same images on paper using three different paints, and they would be just as effective.

The reason these particular illusions work is that the color resolution of our eyes is much worse than the intensity resolution. Our brains form a mental image that attempts to reconstruct high resolution color using just brightness data, with some rough inaccurate color data present: it shouldn't really surprise us that sometimes they're fooled.

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Re: optical illusion

Post by robinson » Wed Oct 24, 2018 6:29 pm

ceptimus wrote:
Wed Oct 24, 2018 4:29 pm
gnome wrote:
Tue Oct 23, 2018 12:55 pm
RGB screens had only three colors too.
Not sure what you mean by RBG screens. If you're referring to the usual sorts of displays used on TVs and computer monitors, then yes, there are usually only three types of phosphor - but usually the intensity of each red, green, or blue phosphor dot can be specified with 5, 6, 8, or more bits of resolution - so these displays can show tens of thousands, up to millions of different colors.

This is different to the optical illusions that really do use only three colors over large areas (many pixels)
Actually it's not that different. When you see a "white" screen on your computer, it actually looks like this.

Image

or this

Image

In fact everything on the screen we see is actually just three colors. Yes, the intensity of the colors changes to allow the illusion of many many colors, but you are always seeing three colors for each pixel, which is a grand illusion.
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Re: optical illusion

Post by Witness » Wed Oct 24, 2018 11:54 pm

What I see is not color mixing, Impressionist (or computer screen) style, but color contrast. Analogous to the same grey appearing lighter or darker when next to black or white.

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Re: optical illusion

Post by Witness » Sun Oct 28, 2018 1:33 am