Color illusions

A forum to ask questions, post setups, and generally discuss anything having to do with photomacrography and photomicroscopy.

Moderators: Pau, rjlittlefield, ChrisR, Chris S.

rjlittlefield
Site Admin
Posts: 21400
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Color illusions

Post by 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:

Large spheres blue-green_smaller.png

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.

Large spheres blue-green_gray_smaller.png

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
Posts: 222
Joined: Mon Nov 11, 2019 7:42 am
Contact:

Re: Color illusions

Post by 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
Posts: 168
Joined: Wed Feb 23, 2011 7:38 am
Location: New Haven, CT, USA

Re: Color illusions

Post by JW »

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

Large spheres blue-green_smaller.png
It's not what you look at that matters, it's what you see - Henry David Thoreau

LouiseScot
Posts: 13
Joined: Thu Jul 30, 2020 8:43 am
Location: Scotland

Re: Color illusions

Post by LouiseScot »

Fascinating! Potential lockdown pastime :D

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

blue-greenoverlay.jpg

Louise

MarkSturtevant
Posts: 1111
Joined: Sat Nov 21, 2015 6:52 pm
Location: Michigan, U.S.A.
Contact:

Re: Color illusions

Post by 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.
Mark Sturtevant
Dept. of Still Waters

LouiseScot
Posts: 13
Joined: Thu Jul 30, 2020 8:43 am
Location: Scotland

Re: Color illusions

Post by LouiseScot »

MarkSturtevant wrote:
Fri Feb 19, 2021 9:17 pm
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
Site Admin
Posts: 21400
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Re: Color illusions

Post by 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
Posts: 13
Joined: Thu Jul 30, 2020 8:43 am
Location: Scotland

Re: Color illusions

Post by LouiseScot »

rjlittlefield wrote:
Sat Feb 27, 2021 5:41 pm
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 :D

Post Reply Previous topicNext topic