Color illusions

[rjlittlefield]

Something inside Google News decided that I'm interested in optical illusions, and it offered me a link to some of the best that I've ever seen.

The main link goes to https://www.dropbox.com/sh/oi9wdd0uc5uc ... 0tma?dl=0. , which offers a bunch of images and brief explanations to go with them.

Various documentation says

David Novick, @NovickProf
Department of Engineering Education and Leadership
The University of Texas at El Paso
http://engineering.utep.edu/novick/
http://www.engineering.utep.edu/novick/colors/

Here is one illusion that I found very impressive:

This one is titled "Large spheres blue-green", and that is exactly what I see: one blue sphere and one green sphere, overlaid by a bunch of colored dots.

But the bodies of the spheres are in fact exactly the same colors, as I confirmed by loading the image into Photoshop, magic-wand selecting the yellow and purple background colors, and converting those pixels to a uniform gray.

For me the illusion is totally compelling. I simply cannot see the two spheres as being the same color, no matter how hard I try to focus attention on the spheres and not the colored dots.

--Rik

[dhmiller]

You might enjoy this book:
Vision and Art: The Biology of Seeing Paperback – April 1, 2008
by Margaret S. Livingstone (Author)

Explains some of the biology of illusions as well as how illusions work in various master artworks. One of my favorite references.

[JW]

Rik - this is intriguing. I combined left half of left side with the right half of the right side, and...

[LouiseScot]

Fascinating! Potential lockdown pastime

Overlay - not blue sphere, not green but blue-green!

Louise

[MarkSturtevant]

That is pretty cool. I do see many examples where similar color combinations are used to induce an after image of a different color.
Among these are animated illusions. Here is one: https://en.wikipedia.org/wiki/Lilac_chaser

Stare at the central cross. There is no green dot.
The link explains some of the reasons for this magic.

[LouiseScot]

That is pretty cool. I do see many examples where similar color combinations are used to induce an after image of a different color.
Among these are animated illusions. Here is one: https://en.wikipedia.org/wiki/Lilac_chaser

Stare at the central cross. There is no green dot.
The link explains some of the reasons for this magic.

That's a cool one! It's these sorts of illusions that convinces me that most people with normal colour vision see colours much the same. Apparently a mutation (most often in women) can give rise to four colour cones - tetrachromacy. What they can see is impossible to imagine, but it must be pretty wild!

[rjlittlefield]

I'm glad to see that other people find these illusions interesting also.

It's these sorts of illusions that convinces me that most people with normal colour vision see colours much the same.

Me too.

But from my standpoint, the most interesting thing is that "much the same" so often means "not what was actually shown".

The reason that the "Large spheres blue-green" image attracted my attention is that it so vividly illustrates the impact that surrounding colors can have on perceptions of other colors.

One of the minor but recurring annoyances in my life takes the form of people gushing about their latest ultra-high-accuracy color calibrated monitor, without giving any indication that they have also calibrated and standardized the environment in which that monitor is viewed. In my opinion, unless you do both it's hardly worth bothering with either. But probably I'm being too much of a stickler. That happens sometimes.

Apparently a mutation (most often in women) can give rise to four colour cones - tetrachromacy.

Yes, fascinating stuff! A good summary at https://en.wikipedia.org/wiki/Tetrachromacy#Humans .

--Rik

[LouiseScot]

I'm glad to see that other people find these illusions interesting also.

It's these sorts of illusions that convinces me that most people with normal colour vision see colours much the same.

Me too.

But from my standpoint, the most interesting thing is that "much the same" so often means "not what was actually shown".

The reason that the "Large spheres blue-green" image attracted my attention is that it so vividly illustrates the impact that surrounding colors can have on perceptions of other colors.

One of the minor but recurring annoyances in my life takes the form of people gushing about their latest ultra-high-accuracy color calibrated monitor, without giving any indication that they have also calibrated and standardized the environment in which that monitor is viewed. In my opinion, unless you do both it's hardly worth bothering with either. But probably I'm being too much of a stickler. That happens sometimes.

Apparently a mutation (most often in women) can give rise to four colour cones - tetrachromacy.

Yes, fascinating stuff! A good summary at https://en.wikipedia.org/wiki/Tetrachromacy#Humans .

--Rik

Yes, a bit like people who spend a fortune on super whizzy loudspeakers and then put them in a cluttered living space