Order of Kilopi
Order of Kilopi
I think it is the brain that's being fooled.
My experience with brain anatomy is somewhat limited, confined mostly to examining road kill. My soul conclusion is that it is mostly made of bluish gray gelatinous stuff, . . .and that I'd like a new one.
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Wow!
Order of Kilopi
Did you know that only the central focal part of your vision is in colour, and the peripheral part is basically b&w? the brain fills in the colour info needed to give a seemingly fully coloured vision. and that's why it remains in colour until you move your eyes. The brain assumes the colours in the peripherical part to be constant as long as it has no new info. So until you move your eyes, you keep on seeing the colours there were before, giving the colour image when added to the B&W. Apparently there is some shift (even inversing) because it seems to be no simple addition of colour and B&W.
Perhaps the long exposure alters the sensitivity of your receptors, making them less sensitive for those colours and hence inversing the colour scheme when these colours are suddenly gone.
But anyway, the basis is in that the brain fills in the peripheral colour info of your vision because your eyes can't see colour in the periphery.
Order of Kilopi
Ok, you´ve got me. I would explain that, but I´d surely spoil it all. I know the explanation the fellows are giving are facetious, of course.
Order of Kilopi
Cool!
Let's see, how can I quickly explain what is going on? The cells that detect colour work in opposition to each other. If you tire one type of cell out by staring at a colour without moving your eyes those cells will get tired. But the cells that are working in opposition don't get tired so that when you look away the cells that are in opposition are working harder than the tired cells. This results in you seeing colour when their isn't any. The tired cells are no longer cancelling out the colours the other cells detect.
Someone else could probably explain this better.
Order of Kilopi
The effect you explained, is the explanation why the colour info is inverse Ronald.
My info on periphery explains why colour remains until you move your eyes.
So it goes like this:
*stare at the dot. You only see colour around the dot, the rest is filled in by the brain, largely remembered from when it was in focus for a brief moment (during the picture scan you did).
*the long exposure tires the receptors for those colours, making you less sensitive to them.
*when these colours go away, you see the inverse colours.
*your brain gets this colour info and uses it to fill in your peripheral view
*only when you look away, the brain sees the real colour info that is now in the new focus point (anywhere on the pic other than the dot, or even outside the picture), and sees that the image in fact is B&W.
There are some small gaps in this explanation, as it would require the brain addition of colour to get tired (or decrease its gain) as well. Or maybe the very few colour receptors in your periphery (or the very brief scanning motions of your eye) make the receptors there tired as well, giving rise to the inversing action in the periphery as well.
But the fact that the periphery is B&W needs to be a factor, it can't be only tiring (overexposing) your receptors as the time to B&W depends on when you move your eyes. Move them immediately, and it goes B&W within one second. Wait longer, and it will remain there very long.
Order of Kilopi
So what I think he does to make it:
*take a colour pic (and add a dot).
*separate B&W and colour info.
*inverse colour info.
Now you need to stare at the inverse colours first. Then the B&W info is added when you move the mouse over it.
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Explanation [highlight the phrase bellow with the mouse]
It´s just a javascript rollover
Order of Kilopi
Argos: no it's not. A Javascript rollover cannot see when you move your eyes. Obviously the switch of the primary strange colour thing to the B&W image is javascript, but there never is a real colour pic shown on screen.It´s just a javascript rollover
Order of Kilopi
Nicolas, such an illusion cannot exist.
<a href="#" onMouseOut="MM_swapImgRestore()" onMouseOver="MM_swapImage('big','','2006_stuffs/manzana2.jpg',1)"><img src="2006_stuffs/manzana1.jpg" name="big" width="720" height="495" border="0"></a></p>
In bold, the two images the author of the trick uses. The event on MouseOver calls the function MM_swapImages.
Order of Kilopi
Yes OF COURSE there are two images. The strange colours you see first, and the B&W in the end. Your explanation requires 3 images, namely also a natural colour photograph.
Check it out yourself, there never is a natural colour jpg into view, and the illusion disappears only at eye movement so that can't be triggered by code.
Or read up on peripheral vs foveal view and colour receptors, that might be informative too.
Order of Kilopi
Don´t be self-deceptive.
Edit: And don´t misguide other people.
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Optical illusions are by definition selfdeceptive, the interesting thing is what they tell about the mechanisms of vision, in this case about coloradaption.
If you load and try to repeatedly reload the second image(on top of itself) you'll see that there is absolutely no color information in it, it's not an animated .gif that fades or anything silly like that.
The interesting thing to to figure out why it's seen as a full color image for a short time after loading when you've been looking at the first image for a while first.
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Reductionist and proud of it.
Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
A person who won't read has no advantage over one who can't read. Mark Twain
Established Member
Oh, this is funny...Originally Posted by Argos
No, there is no trick. It is a real illusion.
Here, look at the two pictures seperately:
http://www.johnsadowski.com/2006_stuffs/manzana1.jpg
and
http://www.johnsadowski.com/2006_stuffs/manzana2.jpg
There is never a color image displayed.
Order of Kilopi
Well, there is, the first image is in color.
The colors are just inverted the right way so that local whitepoint adaption will overcompensate and show colors when it's gone.
Incidentally, just to avoid confusion, you need to have javascript enabled to see the illusion as it depends on switching to a second image.
It took me a while to realise that after waving my mouse around over the first image.
Incidentally that gave a strong clue to how the illusion works, since after looking on the dot for a while the colors looked faded but came back strong in the vicinity of the mouse when I moved it in front of the image.
__________________________________________________
Reductionist and proud of it.
Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
A person who won't read has no advantage over one who can't read. Mark Twain
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AAAAAAAAAAND your pheriphery cannot see colour, it's filled in by the brain. And that's why the colour illusion remains until you move your eyes, not merely until your eyes have recovered from the long exposure.
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And most important of all: don't be overskeptical, or overconfident...
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OK. See a little flag over the tower on the left? I´ve taken a sample of that region on the two images. On the "B&W" one the RGB values are 70,70,70. On the "color" one the values are 89, 134, 93. So, the images are equal?
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The illusion has you so completely fooled that you don't even realize it's an illusion. The author should be proud.
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Ok. NOW I understand it all. Excuse me, I didn´t catch.
Looking with care I can see what the ilusion is about. There is a full color image appearing briefly. I didn´t see it at first.
I thought that you guys were insisting that the first image was Black and white. I´m sorry.
I owe you an appology, Nicolas.
Order of Kilopi
No problem.
Try to focus on the dot for 30 seconds, then move the mouse into the image but KEEP looking onto the dot as long as possible, don't move your eyes at all. The colour image will remain very long. I had it there for more than 10 seconds before I got tired of it
I had problems with overexposure in the simulator: I couldn't see the red line moving on the blue screen after it had been still for a long time. I'll propose a B&W screen some time...
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Order of Kilopi
As I said, that "short while" can be really long if you just hold your eyes focused on the point all the time, also after you moved the mouse. I think that 30 seconds and more must be possible, but I haven't got the patience to check it
Order of Kilopi
Yes.
The brain somehow stores the color information from the first image and combines it with the second B&W image in a sorta CMYK mode.
Vulcan Administrator
I managed to watch it long enough to have it fade from color to black-and-white. Boy, that was strange!
Everything I need to know I learned through Googling.
Established Member
Even worse: If you look at the dot while you have the color illusion going on, if you move away you'll see black and white. BUT, if you quickly come back at the dot, the colors will be back!
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The periphery does have color vision. It may not be as acute as in the center of your vision (the fovea), but it is still there. The center of your vision does not have the low-light rods, your periphery does. But your periphery does have some color-sensetive cones. There are no where near as many color receptors, but there are most definitely still some there.
This really has nothing to do with your photoreceptors getting "tired". Cones can't get "tired" like other neurons, they have a specific adaptation called a "ribbon synapse" that prevents this. They can continue releasing neurotransmitters indefinitely. In reality, looking at an image cannot make your receptors tired, receptors are active in darkness and shut down when light is present, if anything they would be resting when looking at a bright computer screen.
What we are really dealing with here is a phenomenon called "simultaneous color contrast". What happens is that your eyes are set up to filter out changes in scene frequency content. For instance, an apple looks like an apple when out in the sun, in the shade, under fluorescent light, and under incandescent light. In reality the frequency content of the light hitting your eyes is completely different. There are two ways this is accomplished. First, the visual system is set up to filter out changes in the overall frequency content of the scene. So the scene looks largely the same no matter what the frequency of light falling on it is (within certain limits). This happens by supressing cones that are sensetive to a color that is overabundant and reducing supression of cones that are sensetive to a color that is not abundant.
That is not the whole story of what is happening here, although it likely plays a large role (more on that later). What is happening here is what is called "simultaneous color contrast". As was mentioned before, different ganglion cells (the neurons that connect your retina to your brain), are sensetive to different pairs of colors. It may be best stimulated by a red dot surrounded by a green donut or vice versus, or a blue dot surrounded by a yellow donut (or annulus) or vice versus (the dots and donuts being made up of just a handful of cells each). The opposing color to a region's target color falling on that region will inhibit it. For instance if the cell is sensetive to a blue center and a yellow surround, either blue hitting the surround or yellow hitting the center will inhibit it. Thus blue hitting both will cause them to cancel out, as will yellow hitting both. A scene that is uniform in one color will not stimulate these cells at all because the stimulation by regions sensetive to a color will be cancelled out by inhibition by the surrounding regions inhibited by that color. (note these regions are pretty small, a handful of cells). This is called "color opponency".
However, when you combine this with the fact that the visual system tries to correct for changes in scene illumination, it is thought that you get "simultaneous color contrast". Although simultaneous color contrast is known, the exact mechanism is not clear. However, here is probably the most likely reason. The output of the receptors in your visual system adapt to changes in frequency content in the environment in order to maintain a constant color to the environment (note that the receptor electrical activity remains the same, only their output changes). In the image you saw, there is an overabundance of some colors in some areas. Your visual system corrects for this by reducing the output of the receptors sensetive to those colors. Under normal conditions this would correct for gradual changes in spectral content in a scene. This supression does not change instanteously, it takes time (this makes normal, gradual color changes more subtle and thus less noticable).
What happens when you suddenly eliminate those frequencies from the visual scene is that the receptors sensetive to those colors are still being supressed for a period of time. However, suddenly you have a scene with all or no frequencies present (black or white). That means that the colors you were looking at are being supressed, but the colors you were not looking at are being detected normally. Due to the opponency effect, the receptors that were sensetive to the colors in the original scene, and thus are opponent to and thus supressing the colors not present in the original image, are being supressed themselves. Since they are no longer active, they are unable to supress their opponent colors anymore so you see an overabundance of those opponent colors. The colors that were not present, however, now are present, allowing them to supress the already partially-supressed original colors, making those parts of the spectrum disappear. What you are left with is the colors that were previously present being supressed, while the colors that were previously absent being unsupressed (thus enhanced).
Similar things happen with black and white, due to overall contrast as opposed to individual color contrast.
Now at least in Cyprinid fish, the only one I am aware of with a working computational model on the subject, it appears that this is mostly operating in the earliest stages of the retina, with a network called the horizontal cell network directly altering photo receptor output both for color contrast and color opponency. It is not clear whether this is the case with primates or not, but considering how similar all vertebrate retinas are it very well might be. The phenomenon itself is certainly the same, even if the cause is not.
Now I should point out one thing. In reality when I say a receptor is supressed or not being stimulated, what actually means is it becomes more active. A receptor that is being stimulated becomes less active. This may seem counterintuitive, but photoreceptors are shut down by light, or by the color they are sensetive to, and become more active in the dark. Your retina is actually the most active when you are asleep. I didn't use the correct terminology through this post because it is not important in this case and makes things hard to follow, but it is something to keep in mind.
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Hmmm... My guess is that when looking at the image with the (complimentary) croma information, the eye will lose sensitivity to those colors in those areas due to depletion of photosensitive chemicals in the coresponding cones, thereby gaining sensitivity to the complimentary colors of this. Then displaying the luminance image will mean that the eye will se the hues it is now more sensitive to. As long as you do not move the eyes, the grayscale of the second image will deplete the cones of all colors at a similar rate, and so the relative depletion will remain for a while(of course, as a cone get more and more depleted, the rate of depletion will decrease, and the previously less depleted cones will catch up, so the effect fades) . Moving the eyes destroy the effect because the persistant image caused by the depletion and the real image no longer overlap, my guess is that the brain is wired to suppress persistant images, there is probably no natural circumstances where you can get the effect caused by this illusion, and so the brain never learn to suppress persistant color caused by depletion when the color patern matches what you currently see. Since you have moved your eye, the effect that would keep the illusion persistant longer(the balanced depletion I mentioned earlier) will also be broken.
I do not think the effect that the brain fills in color is a major cause of the illusion. The eye can detect color in the entrire field of view, it isn't colorblind everywhere but the center of the field, however, it is true that the fovea have the highest density of cones, and the color sensitivity drops of the further from this you get. If you do not look at the spot in the middle of the image, but outside the image, you would still get the same effect when switching images, it is important to keep the eye still, it will perhaps seem a bit unfamiliar to keep your attention on something outside the sharpest part of your field of view, and your eyes might want to move towards the object of attention.
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Your retina is quite capable of keeping the pigment level constant, at least for cones. That is not the issue here. It has to do with your retina trying to make sure you percieve the same colors regardless of the frequency content in the environment. If the pigment level gets depleted you go blind (that happens with rods in anything other than very dark environments). That does not happen with cones, in fact your cones will be destroyed long before you get enough light intensity to seriously overwhelm the refilling mechanisms (assuming nothing disrupts retinal metabolism, the low pressure and thus low oxygen in an airliner is enough to dim vision somewhat).
This is not happening in your brain, at least not entirely, much or all of it is happening in your retina (that much is clear, at least it is for lower vertebrates whose eyes are pretty much the same as ours). And your retina does not supress persistant images, it supresses changes in color content or overall ambient illumination level. Moving your eyes too much (it is impossible to keep your eyes perfectly still) means the receptors are getting changing frequency contents and thus don't have a chance to adapt to one specific set of frequencies.
Last edited by TheBlackCat; 2006-Jun-09 at 06:36 PM.
Order of Kilopi
So it is as I said that it's the whitepoint compensation that's fooled.
__________________________________________________
Reductionist and proud of it.
Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
A person who won't read has no advantage over one who can't read. Mark Twain
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