False Color Illusion (APOD 17 July 2007)

[DONHELL]

It seems to me that the geometry of the graph would prove the colors are different. The grid pattern shows left right and top bottom dissimilarity in block color. As well, the squares that are only partially obscured should reveal a blending of two colors to provide a comparison. If the black white pattern of the grid was changed in this case (i.e, the color of 'B') solely for illustration the answer is still difficult to accept because the color of the diagonal squares to 'B' remain the same as 'B' and are merely shaded, not the same color as 'A'

[craterchains]

Fascinating, , ,

I had to download the image and run it through a color match program to believe it. Remarkable, but true.

[Stardance]

Personally, I don't see the "illusion" even when the two squares are connected with a rectangle that allegedly contains the "same color" as the respective squares. Square A has a relatively dark shade of what appears to be "gray", and Square B has a relatively light shade of what appears to be "gray", i.e., the color of the respective squares is the same, just the shade is different. With the rectangle, Square A has a somewhat lighter shade of gray than without the rectangle, but it is still darker than Square B; the rectangle does not appear to have a uniform shade of gray in all of its area, and Square B has a lighter shade of gray than the rectangle.

Note that the "color" is not in the ROYGBIV spectrum. Does the "illusion" work for shades of other colors such as red or blue??

So, what is the "illusion"?? Is the "shadow" cast by the cylinder supposed to affect how the color of Square B is perceived?? To me, at least, the two squares are not identical in appearance, and the case has not been made that they are identical in fact. FWIW, I am red-green "color blind", and I have excellent discrimination of black/white and all "shades of gray" between the total absence of light (black) and the total presence of light that comprises all colors of the spectrum in combination (white).

[Sudhamshu]

I too have got difficulty in understanding how the colours are the same. It seems like a gradient on the gray scale. Was hoping the explanation on APOD itself would explain. But the explanation is not satisfactory. Now i'm hoping some genius out here will elucidate upon this mystery.

[craterchains]

The Same Color Illusion
Credit: Edward H. Adelson, Wikipedia
Explanation: Are square A and B the same color? They are. Are too. To verify this, click on the above image to see them connected. The above illusion, called the same color illusion, illustrates that purely human observations in science may be ambiguous or inaccurate. Even such a seemingly direct perception as relative color. Similar illusions exist on the sky, such as the size of the Moon near the horizon, or the apparent shapes of astronomical objects. The advent of automated, reproducible, measuring devices such as CCDs have made science in general and astronomy in particular less prone to, but not free of, human-biased illusions.

Color has nothing to do with the image. Misinformation here.
My opinion of the writer of this article is VERY biased against humans.

[Qev]

Human senses are notoriously unreliable for precise measurements of certain properties of things. It's not anti-human, it's just fact.

Though I agree, it's more a matter of value in this image, since there aren't really any colours involved. I suppose they're using 'colour' in the colloquial sense.

[makc]

It seems like a gradient on the gray scale.

It does to me, too. I think this is better image.

[Nancy D]

I printed the image, cut out the two parallelograms with scissors, and when they were separated from the image, yes, they were the same color. Until then, I couldn't perceive that they were the same color.

[jimmysnyder]

What I recommend you do is take a piece of paper and cut out two holes in it so that the holes line up with the squares A and B. This works for me much better than the other attempts to show that the colors of A and B are the same.

[Sudhamshu]

It does to me, too. I think this is better image.

Yeah that certainly is a better image. So what it means is that, the shadow falling on the lighter gray square (Square B) makes it as dark as Square A. But instead of comparing A & B, we compare B and its adjacent dark square. "Now I'm a believer"

[prof_rocko]

You can also just cover up the green object with you hands (works better in the image with the connecting bar). Sudhamshu, I also thought the connecting bar between A and B looked like a color gradient (hence A and B were not the same color), but when you cover up everything except A, B, and the bar, it is clear that the gradient is merely an illusion caused by your eye in response to the apparent shadow of the green object.

Cool!

[iamlucky13]

A very easy way to test the claim of the APOD:

Copy the picture
- Right click on the picture. Select "copy"

Paste in to Paint
- In Windows, go to Start > Run, type "mspaint" and click "Ok"
- In Paint, go to Edit > Paste

Now use the color select tool (it looks like an eyedropper) to select the color from either A or B. Then use the paintbrush tool to paint with this color in the other square. Same color!

Of course, there is a distinction between the recorded or perceived color and the actual color. If this were a real object, the actual color would be the different, but the lighting conditions are what make it look the same.


Now for extra credit go to your favorite search engine and do an image search for Escher.

[mesaxi]

the point made in the summary reminds me of "Rendezvous with Rama". It takes place in the 22nd century and human astronomers mistake an abandoned alien craft for an asteroid.

The question is, how many previously precieved concepts may be rendered moot by technology, and how will that affect our future preceptions of the universe. As of now we have a clearly defined boundary of the universe, but we may find more beyond the border or something.

Another question is, where should we draw the line with letting technology do things for us? I know it has its benefits in subjects such as that under discussion, but there will be downsides as well (reliance, cost, etc)

[DONHELL]

People seem to be using subjective criteria to prove objective facts here. It is dificult to prove color exists except by popular agreement. Color seems to be "in the eye of the beholder." But according to the alternating pattern of the squares, in this APOD example, if squares A and B are the same 'color' then all squares are the same, otherwise the pattern doesn't hold thus revealing trickery of another kind. The shadow of the cylinder would have peculiar properties indeed were it able to change the color of only one square. All it may do is shade the square. The shading would obviously be different between the two squares but I'm told they are the same color instead which seems to go against reason.

A more important exercise may be how to disprove a fabricated illusion?

Benjamin Franklin said: "When the lights are low, all cats are grey."

[Qev]

That's the trick, you see. The two squares -are- identical in colour (or value, if you prefer, since they're grey); it's simply that the surroundings in which they are presented create a scene that we interpret as three-dimensional, with a shadow. Thus, our brains interpret the colours incorrectly.

But there is no three-dimensional scene, there is no shadow. It's a flat image, and the two squares have identical colours.

[Nancy D]

Try this: print the image twice. Cut out one of the parallelograms. On the other page, place the parallelogram over the A space, then slide it down to the B space. Yikes!! Watch it change color in your perception!

[dictostelium]

This is insidious stuff. The corollary from this demonstration is that human senses are unreliable, and then the conclusion usually drawn is that you can NEVER trust ANY sensed information, and then the only real facts are ones which are measurable in a randomised double blind trial using laboratory instrumentation. I've seen the argument used so many times to deny almost any subjective reality you can care you think of.

Actually, there is another, exactly opposite illusion - compare Bud***** to tapwater, and you will notice that one is more yellow than the other - however, this is an illusion, because they are BOTH tapwater.

[bluekron77]

I couldn't just take their word for it
so I made this little animation to illustrate
how I had to see it, to believe it...