Reblogged: A Quick Thought on Perception

[dianahsieh]

David Smith tweeted: “Mind = blown. These two blocks are exactly the same shade of grey. Hold your finger over the seam and check.”

I’d like to do some more thinking on perceptual illusions. I don’t think that the grays look different due to any conceptual inference. The grays look very different, until the seam is covered, and then they look the same.

Yet I don’t think that these are “perceptual errors.” Rather, this is exactly how our perceptual system is supposed to work, perhaps because such mechanisms enable us to properly judge shades and depth in the real world. However, particular with computer images, we can reveal these oddities and limits in our perceptual systems in a stark way.

Notably, these kinds of cases are very different from many traditional illusions like a stick bent in water, which are a function of the medium of perception (i.e. air versus water). Still, I don’t think that they reveal that our senses aren’t reliable or valid: they just reveal, in yet another stark way, that the diaphanous model of perception is wrong.

Thoughts?

Link to Original

[CrowEpistemologist]

This is an aside, but this is a fun example of how colors work.

 

Colors, remember, are a combination of the nature of the object and the nature of the light illuminating the object. While the middle-body areas of the blocks in the image above are exactly the same color, the edges are not--they are drastically different. (Hence if one were to be a bit pedantic about this, you would say that the blocks in this image are not the same at all in this computer image).

 

Interestingly, I suspect that if you performed this experiment in the context of real-life (i.e. a real physical block in a lighted room), your brain would probably compensate for the different angles of light and conclude the block was the same color.

[Plasmatic]

Maybe something is wrong with my eyes..... but the bottom grey still appears lighter when I cover the middle.

[CrowEpistemologist]

Maybe something is wrong with my eyes..... but the bottom grey still appears lighter when I cover the middle.

 

You have to focus on just the middle part since the edges are in fact a different color... This is a weird example....

[aleph_1]

The color illusions given here http://serendip.brynmawr.edu/bb/contrastcolor/    do not have different color edges. I think that Objectivists should and do accept the metaphysically given. These illustrations demonstrate something about how the mind works in relation to vision. In no way do they alter belief that we may reliably use our perceptions to make life choices. All perception is filtered prior to being raised to the level of consciousness. This filtering process can be lifesaving, but it can also lead to quirks such as these.

[whYNOT]

Maybe something is wrong with my eyes..... but the bottom grey still appears lighter when I cover the middle.

There is a tiny "fudge factor", which I feel was hardly necessary to still make its point . I made several tests on the image with a photo light meter because I believed I saw what you have - and there is a consistent +/- one-eighth of a stop difference between the greys. Just detectable to the eye.

[Plasmatic]

There is a tiny "fudge factor", which I feel was hardly necessary to still make its point . I made several tests on the image with a photo light meter because I believed I saw what you have - and there is a consistent +/- one-eighth of a stop difference between the greys. Just detectable to the eye.

Thanks for that info. I guess all those years doing black and white portraits makes me a bit more sensitive to value and shade nuances.

[Grames]

Those blocks are not even close to the same shade of gray.  The parts of the two blocks that are in the same direct light and the parts of the blocks in the same weak indirect light consisently show the bottom block is lighter, and can even be described as white.

 

The fact that the top of the dark block in strong direct light has the same shade (or almost the same) as the bottom of the white block in weak indirect light does not mean that the blocks themselves are the same color.  Any ordinary common sense assertions about the colors of the blocks would compare them in equal lighting.   In order to present the same appearance in such different lighting conditions the surfaces would have to be of different shades.

 

Now in this last paragraph of mine am I performing acts or reason or simply remembering and describing how things really looked in past instances of my own experiences with light and shadow?  The application of the concept of a shadow (a first level concept) is at once both automatized and produces an induction. so the answer is both.

[Eiuol]

The fact that the top of the dark block in strong direct light has the same shade (or almost the same) as the bottom of the white block in weak indirect light does not mean that the blocks themselves are the same color.  Any ordinary common sense assertions about the colors of the blocks would compare them in equal lighting.   In order to present the same appearance in such different lighting conditions the surfaces would have to be of different shades.

That's kind of the point. On my screen, the gray portions are identical when I check with the eyedrop tool in paint. It's possible that any difference people see is due to how their browser renders the image. The grays are the same literally speaking. The reason the two are judged is due to the lighting, as you say. If lighting was equal, the gray would be judged as identical. I'm avoiding saying "perceived as gray", since there's a difference between "my intuition is that these colors are identical" versus "my eyes literally take these two colors and makes them different". The parts in the same weak indirect light are the same color, but their luminosity is different. That's why the word color is too vague. The grays are the same hue and saturation. I'd say the colors are processed, not filtered as Aleph said, Nothing is being taken away in order to see, as filter would imply. Interpreted wouldn't be accurate either, since it's not as though depth and luminosity is not "really" there.

 

I doubt anyone would say that seeing depth is also an illusion. The image is 2D, but looks 3D. Some may say graphics in video games fool you into seeing 3D. Except, no one is fooled. Any and all vision starts as 2D and upside down anyway... Really, perceptual processes just highlight information that exists, and also make some information less salient (it's interesting that perceptual psychology has a lot to do with exploring why and how information gets different levels of focus/attention).

[Plasmatic]

Louie said:

"It's possible that any difference people see is due to how their browser renders the image."

Im not a tech guy but if the same browser is rendering the same "information" (the alleged identical top and bottom shades of grey) then how could it end up as different?

[Plasmatic]

Delete please

Edited December 12, 2013 by Plasmatic

[dream_weaver]

 Something like  would illustrate the point with much less discrepincy among monitors.

[whYNOT]

Louie said:

"It's possible that any difference people see is due to how their browser renders the image."

Im not a tech guy but if the same browser is rendering the same "information" (the alleged identical top and bottom shades of grey) then how could it end up as different?

 The monitor shouldn't make a difference, as you say. I'm still getting the same result with my light meter.  Like you, I've also spent much time with b+w shooting and printing, and I'm wondering if we developed a heightened perception of tonal distinctions in the grey scale, as result. Interesting...