September 27, 2002

1:27 AM

A professor of vision science at MIT understands that life isn't just black and white, even though we often see it that way. This amazing illusion proves it, and these slick, fast-loading, Flash demonstrations of lightness perception show how it's done. (My favorite is the "Koffka Ring".) White paper here, for deeper background.
posted by taz (29 comments total)

(I came across the checker-shadow illusion via interconnected, who found it via scribot.)

posted by taz at 1:29 AM on September 27, 2002

I don't get the check-shadow illusion - is the letter B the same shade of gray as the square A? Or are both squares gray?

Cool illusions, I always do enjoy not believing my eyes..
posted by Mossy at 2:09 AM on September 27, 2002

No Mossy, both squares are the same shade of grey. I couldn't believe it until I shielded the other squares off.
posted by salmacis at 2:13 AM on September 27, 2002

wow, this is very cool stuff. i think my favorite is the impossible steps. i will definately read the white paper tomorrow in my more awake state. thanks taz!
posted by escher at 2:30 AM on September 27, 2002

That check-shadow illusion is wild! I couldn't believe it until, like salmacis, I masked off the other squares. The lettering in the squares contributes to the illusion too I think.

Thanks for the link taz - printing off the white paper now!
posted by jiroczech at 2:48 AM on September 27, 2002

I have always (always, in this case, refering to a period of about ten years, or since I was eleven) wondered what the world would look like without the contrast enhancement our brains give everything. Examples like these show that, in some cases at least, the difference would be dramatic.
posted by Nothing at 3:04 AM on September 27, 2002

That check-shadow illusion is wild!

Exactly. I couldn't believe my eyes until I saved the pic, copied square B, and pasted it directly next to the square A.
I'm still amazed.
posted by gummi at 3:18 AM on September 27, 2002

Lordy, so they are. I masked it off using three fingers on each fingers - its odd how the A square gets darker if you let some of the dark squares near it into the frame. Lets look at that whitepaper..
posted by Mossy at 3:19 AM on September 27, 2002

printing off the white paper now!

Are you sure that the paper is white jiroczech... it may just look white against that background :)

I didn't believe this illusion until I chopped a circle out of the B square with Photoshop and moved it onto square A. Mind you, neither did any of my work mates.
posted by DrDoberman at 3:19 AM on September 27, 2002

But why? Not understanding has got to be part of the pleasure. Great post, taz - it is you, isn't it? I wonder whether the same illusion could be applied to the exciting boring new world of grey literature. All those documents still look the same to me...
posted by MiguelCardoso at 3:31 AM on September 27, 2002

yes, 'tis me, though if you think you know me from somewhere other than MF, probably not.

Nice link on "grey literature"; I especially liked the referencing of "Bradford Gray" as a source.
posted by taz at 3:39 AM on September 27, 2002

laugh @ DrDoberman..

I was trying to explain to my 5yr old the other day, while he was colouring in, how stuff isn't ever just one colour.

I tried explaining about highlights and shadows but for him a red brick is just .. you know, red. I mean if you look at it all over, every bit of it is the same red so why should you colour it in any other way than red all over?

Kids make good philosophers.

PS. I was going to tackle his views on phenomenalism but, hey, BeyBlade was coming on..
posted by jiroczech at 3:51 AM on September 27, 2002

Even better, if you have Photoshop, is to select the two squares of the checkerboard illusion using the polygonal lasso or the magic wand, invert the selection, and then delete the background... then undo the deletion... and delete, and undo... the B square seems to change colour before your eyes.
posted by rory at 4:07 AM on September 27, 2002

You see a similar effect every time you watch television. Think of the black on a television screen. Compare it to the colour of your screen when its turned off. The black when its on looks darker than your screen when its turned off. This is an optical illusion as well, you can't make the screen any darker than its inactive state, but your brain interprets data based on contrast.
posted by substrate at 5:35 AM on September 27, 2002

Here is a brief primer on the Gestalt psychology "laws of perception", and here are some more experiments and such. Interesting stuff.
posted by Fabulon7 at 5:49 AM on September 27, 2002

Wowie. This is a fascinating set of links, taz - thanks!

Mossy - maybe it's just me, but it appears that you have quite an illusion going too:
I masked it off using three fingers on each fingers
posted by madamjujujive at 6:53 AM on September 27, 2002

Ah, I LOVE this stuff, which is why I studied it in college...

It applies not only to black/white/grey squares, but also to color. Many times I had to convince a designer friend that the two colors she'd used in a design were indeed different, even though upon initial inspection they looked the same (and sometimes vice versa.)

The brain is a master at taking averages and guessing about what it perceives. That's what makes finding faults in the system so incredibly cool! If anyone is looking for some additional reading I'd recommend the rather technical Foundations of Vision by Brian A. Wandell (can be found online, I'll leave it to you to select your favorite bookstore.) It takes a closer look at the math and physics behind the visual system.

Thanks for posting this link and pointing out this wondrous phenomenon to the MeFi community!!!
posted by absquatulate at 7:15 AM on September 27, 2002

This illusion is similar to using a projector on a white screen in a not-completely-dark room. Dark-colored elements will only be as dark as the surface of the screen, since the projector can only emit light and not remove it.

jiroczech, you're right — the lettering does contribute to the effect.
posted by dayvin at 7:45 AM on September 27, 2002

Thanks for the links! This is why I love mefi!

Oh yeah, I loved the music in the flash stuff? Anyone recognize it?
posted by internal at 7:52 AM on September 27, 2002

Great illusions, especially that checker-shadow one. I'll never believe my own eyes again.

Makes you wonder, what if they made the "identical" squares/rings/etc. different shades every so often, just for laughs?
posted by gottabefunky at 8:15 AM on September 27, 2002

We had to *make* these things in my color theory class in college. We did them in color, though, using this stuff called "color-aid", 500 sheets of silkscreened paper that ran all though the visible spectrum. The idea was to make a green look like a blue (or a grey look like a dark red, and so on), and vise-versa by manipulating the colors surrounding them. It's pretty hard to do.

A lot of the simultaneous-contrast stuff was pioneered by Josef Albers, an interesting fellow in his own right.
posted by interrobang at 8:19 AM on September 27, 2002

I don't have photoshop, so I just printed out a picture of the checkerboard, then cut out the squares with scissors. The squares seemed to change color as I cut them.
posted by tdismukes at 10:05 AM on September 27, 2002

Best post all week, IMHO. Thanks, Taz!
posted by Lynsey at 11:22 AM on September 27, 2002

A related illusion (relating to color rather than contrast) can be found in photos like this one which seem to contain colors that they do not in fact contain. (There are no green pixels in the image in that link, only various shades of red and gray.)

Explanation here. The illusion was invented/discovered by Edwin Land of Polaroid fame and is called Retinex. (And yes, that's the Web site of the same Wendy Carlos who did "Switched-On Bach" and the music for Tron.)
posted by kindall at 11:44 AM on September 27, 2002

If you don't want to use Photoshop or the print-and-cut method to unravel this illusion, just sit about 3-4 feet away from your screen and cross your eyes and/or allow them to relax. Ta-da!
posted by dayvin at 1:14 PM on September 27, 2002

Very, very cool. Thanks, Taz.
posted by ptermit at 2:14 PM on September 27, 2002

white is the new black, or something.
i just can't believe my eyes!
does anybody know of any internal decoration books that discuss using this phenomina in a domestic setting?
posted by asok at 2:25 PM on September 27, 2002

Many times I had to convince a designer friend that the two colors she'd used in a design were indeed different

If she designed it, how did she not know that?

using this stuff called "color-aid", 500 sheets of silkscreened paper that ran all though the visible spectrum

I remember that stuff from my foundation year of art school (though I don't remember that being the name - is there another brand?)... I hated it then because I was a messy "fine arts" type and all the japanese girls were able to make such perfect illusions. It's really unfortunate how much more interesting school seems now that I'm too old to expect my parents to pay for it anymore...
posted by mdn at 4:27 PM on September 27, 2002

Lots of fun. I haven't done this since I threw out my Color Aid pack.
(Do they still use those?)
posted by HTuttle at 10:41 AM on September 28, 2002