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

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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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:
All of you are probably familiar with color opponency, but just in case, I'll give you a quick refresher. I'll even start with the history. In the 19th century, there were two competing theories of color vision. The first was the Young-Helmholtz theory (sometimes called the trichromatic theory),…
This is a guest post by Suzie Eckl, one of Greta's top student writers for Spring 2007 Forget color television. Before we had color, we had black and white. Before we had movies, we had photographs. And before photographs we had... Engravings? Prior to August 19, 1839, the date Daguerre and…
So how does Superman do it! He can see through buildings and clothing (he checks out Lois Lane's underwear in Superman 1 - more on this later). Many have attempted to answer this question of the ages yet few have explored this in as much depth as J.B. Pittenger who published a study in the…

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.

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 thatâs always impressed me is how each cone type has a nearly perfect tiling across the retina, irrespective of the other cone types.

By Dan Clark (not verified) on 02 Jul 2009 #permalink

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?

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.

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.

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

By Llewellyn Kriel (not verified) on 22 Aug 2009 #permalink

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

Good luck with your PhD thesis.

How does your research accommodate Edwin H. Land's two-color representations (retinex theory), as opposed to standard three-color representations?

Greetings! I'm a Michigan alum who wrote a dissertation on the psychology of emotion and shame in particular. I'm fascinated by the brain and how emotions work. I blog at http://livewithflair.blogspot.com/ as a way to create happiness by finding the extraordinary meaning in the common thing. It turns out that you can change your mood much more easily than we think.

Science?

Just like this clip is trying to make believers out of all of us via the "don't believe what you see" theory, it is also manipulating viewers because seriously, you shouldn't just believe what you see...

Start video at 28 second mark which will reduce burn in time. Result is the same and theoretically it shouldn't be because your eyes are "supposed" to stare at it for 20 seconds first to "burn in" the color from the negative.

What do I see? It looks like creator has manipulated the still frames at 31 seconds, dropping in a couple 1/30 color slides. Some people perceive it while others don't. It's flash sublimination.

To disprove this you should be given the option of watching the presentation backwards, but you can't.

That's awesome! There should be some instructions though to look at the dot... That might clear up some of the problems people are having.

Cool,

I studied reverse-engineering MRI scans of the visual cortex, (V1-5) for my MSc project.

That's really interesting, and I'll be following your posts with interests.

Cheers,
Tom