A very cool optical illusion

[mdlbear]

From BoingBoing (of course), Mr Angry and Mrs Calm -- an angry and calm face that trade places when viewed from a distance. There's more here (you have to scroll down for it), including a brief explanation.

The trick is that the two faces are blends: one has the high-frequency components of an angry face laid on top of the low-frequency components of a calm face; the other one is the reverse. So when you're close, you see the high-frequency details; when you're far enough away the details average out and you're left with the low frequency components.

It's somewhat related to the infinitely-descending scale, where each note has a different balance of high and low overtones. (Gotta make myself a set of those soon -- I have a use for them.) It's also very closely related to wavelet compression, as found in JPEG 2000 compression (and which some of my coworkers were heavily involved with).

Comments

[vixyish.livejournal.com]

Hot damn, that's cool! We actually tried it by walking across the room and back-- weirdest to see it when you do that without taking your eyes off it, and watch it change.

Funny thing-- I don't know if it's my particular eyesight or what, but if I just squint at them, they *both* average out to something in the middle, neither angry nor calm but something like mildly annoyed. :)

[mdlbear]

That's because squinting blurs the image, which has the same effect on the high spatial frequencies as distance. So if they average out, you're seeing them as if you were at some in-between distance where the high frequencies are blurred about 50%.

Robin

[capplor.livejournal.com]

Real cool. I'd already been playing with image filters, and discovered that a low-bandpass was pretty much what I see without glasses. Sure enough, remove the specs, see the other image.

[ashi.livejournal.com]

Broken images currently. I think it's been Boing-Boinged.

[ashi.livejournal.com]

This one has a local copy of the image:
http://metamerist.blogspot.com/