Color after image demonstration - Seeing color when there is none. : Of Two Minds

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Shelley Batts is a Neuroscience PhD candidate at the University of Michigan. She studies hair cell regeneration in the cochlea, and is trying to finish that quixotic quest called 'thesis.' She lies awake at night pondering how science intersects with politics, culture, policy, money, medicine, and religion in an attempt to be more than just a niche scientist sitting in the oh-so-lovely ivory tower. Follow me and my parrot, Pepper, on our quest to finish my PhD, land a post-doc, and stay sane.

The Omnibrain is a psychology graduate student at an online university. He hopes that the three weeks and $29.95 that he is spending on his Ph.D. will get him a job at a Tier 1 research university. Do online universities have postdocs? Ok...just kidding, he is really a Ph.D. Candidate in Psychology studying high level vision. You know... stuff like scene & object perception.

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Color after image demonstration - Seeing color when there is none.

Category: Psychology • Vision
Posted on: July 1, 2009 11:29 AM, by The Omnibrain

I'm teaching about opponent processes in color vision today and thought I'd share one of my favorite examples. This is how you use the human visual system to turn a black and white photo into color. Try it out:

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Comments

Very interesting.
I learned about opponent color processing in a nice little paper by neurophilosopher Paul Churchland named "Chimerical Colors", where he shows that the phenomenal color-space (the hue-circle with the added light-dark axis) is isomorphic to the output-space of the Hurvich-Jameson model for color-processing, thus allowing an ontological reduction of color-qualia to visual processing in an HJ-network. He even provided examples of "chimerical colors" where you look at a certain color, and then, instead of looking at a neutral background, look at a background of a certain (different) color, thus producing impressions of colors that we could not otherwise see. Very interesting - and impressive.

One thing that has been bugging me, though - why do negatives of images always look like they have a far narrower color-range than the corresponding positive? Perhaps someone here can enlighten me.

Posted by: MPhil | July 1, 2009 1:55 PM

The apparent narrow color-range of a negative image is due to the dynamic range of the cone receptors in the retina. The three cone receptor types we have are differentially activated by a given color scene (the Wikipedia entry on color vision has a decent write-up of this). A negative of a given color scene has a very different set of wavelengths, many of which fall outside the dynamic range of human color vision of around 425nm-625nm.

On another note, one thing that’s always impressed me is how each cone type has a nearly perfect tiling across the retina, irrespective of the other cone types.

Posted by: Dan Clark | July 2, 2009 2:31 PM

Very cool! As the video is loading, I concentrate on the dot in the center of the image. When the image shifts to B&W, I can see the narrow color range, but I note that when I shift my focus off the center point, the colors go away, but return once I go back to the center. Is that an expected outcome?

Posted by: The skepTick | July 6, 2009 3:48 PM

good,
ı concentrate on the center the image, ı see color range.

it's very interesting. Thank you

Posted by: Psikolog Uğur DALAN | July 10, 2009 5:18 AM

This doesn't work very well for me. When the image shifts, I think I may imagine a slight hint of colour, but when I acutally look at the image, it is black and white.

Posted by: Marcia | July 10, 2009 12:14 PM

Thank you. but ı actually look at the B&W image.

Çocuk Psikolojisi

Posted by: çocuk psikolojisi | July 11, 2009 1:14 PM

I wonder why it works for some people but not others.

To see an afterimage, I have to stare at an extremely bright light. A video on a computer screen in normal room lighting isn't going to do it for me.

Posted by: Marcia | July 20, 2009 7:37 AM

What happened to Shelley Batts? Is she married now? She never writes in this blog any more. How is she doing?

Posted by: William Petersen | July 21, 2009 9:29 PM

I'm sorry, but I missed this entirely. All I saw was a black and white image - what else was I supposed to see?

Posted by: Llewellyn Kriel | August 22, 2009 2:30 PM

Great blog! This video is now on my bookmark list and I've had a great time reading all your posts.