Thread: Visual Phenomena & Optical Illusions

Illusionary Light-"Emittence":





Happy Reflections:





Now something delicious - if only they had used a high-speed camera for this..

Originally Posted by guyism

What do you get when you combine a spinning chocolate sculpture and a perfectly timed strobe light? A mind-blowing optical illusion.
This is an exhibit at Melbourne’s Phillip Island Chocolate Factory, not to be confused with R. Kelly’s Chocolate Facotry. If you look closely as the sculpture starts to spin, it’s obvious how it works, but that isn’t the point. It looks awesome. I didn’t quite have the same emotional experience as the guy who said, “Now I’ve seen it all!” though.

If this can be called a phenakistoscope, like somebody suggested, I have only ever seen the two-dimensional versions, like the one from Wikipedia below.

Originally Posted by Wikipedia

The phenakistoscope (also spelled phenakistiscope or phenakitiscope) was an early animation device that used the persistence of vision principle to create an illusion of motion.

Although the principle behind the phenakistoscope had been recognized by the Greek mathematician Euclid and later in experiments by Newton, it was not until 1829 that this idea became firmly established by Belgian Joseph Plateau. Plateau planned it in 1839 and invented it in 1841. Later the same year the Austrian Simon von Stampfer invented the stroboscopic disk, a similar machine. A contemporary edition of Britannica says "The phenakistoscope or magic disc...was originally invented by Dr. Roget, and improved by M. Plateau, at Brussels, and Dr. Faraday."

Technology

The phenakistoscope used a spinning disc attached vertically to a handle. Arrayed around the disc's center were a series of drawings showing phases of the animation, and cut through it were a series of equally spaced radial slits. The user would spin the disc and look through the moving slits at the disc's reflection in a mirror. The scanning of the slits across the reflected images kept them from simply blurring together, so that the user would see a rapid succession of images that appeared to be a single moving picture.

A variant of it had two discs, one with slits and one with pictures; this was slightly more unwieldy but needed no mirror. Unlike the zoetrope and its successors, the phenakistoscope could only practically be used by one person at a time.

Etymology

The first part of the term 'phenakistoscope' comes from Greek φενακίζειν (phenakizein), meaning "to deceive, to cheat", as it deceives the eye by making the objects in the pictures appear to move.

Alternate names

Online sources sometimes refer to this invention as the Phantasmascope or the Phantascope. However, Phantascope is also the name given to two different, later, projection-based moving picture devices by John Arthur Roebuck Rudge.

Today

The Special Honorary Joseph Plateau Award, a replica of Plateau's original phenakistiscope, is presented every year to a special guest of the Flanders International Film Festival whose achievements have earned a special and distinct place in the history of international film making.



Link To Video - Disk in Action*

*too big for here.. hm... maybe for youtube as well..

Originally Posted by StephL

Illusionary Light-"Emittence":

That's an interesting one I've never seen before, thanks for posting. I looked at it for a bit, not understanding what the illusion was. Of course I couldn't stare at it for more than a second before the light felt too bright and I kept scrolling down. Then I realized way embarrassingly late - that was it! Bright light can't emit from a computer screen.

Originally Posted by snoop

To get the spinning woman to switch directions all I have to do is close my eyes and visualize her spinning in the opposite direction, or if that doesn't work (which it occasionally doesn't) I focus my attention on the foots reflection and then switch back and forth looking at the foot and its reflection while imagining her spinning the opposite direction. Almost always works for me.

[edit]
The cat is easier to switch. Once you realize the illusion is in that the cat is actually spinning at all, you imagine it going the opposite way when it's facing "backwards" and since there are less frames it switches more easily.

The face one makes sense how it works. The finer detail is visible only from close up, but the shadow and lighting detail becomes apparent as the finer detail is lost due to distance. It looks like they took two pictures of two different expressions, took them in photoshop, made a high pass filter of both and copied and pasted the opposite face and overlayed them onto each other, while mildly blurring the original background image. That one makes much more sense than the spinning cat and woman imo.

[edit 2]
That's what I get for just looking at illusion and not reading the post--didn't realize the face one was already explained.

Wow - great tips!
Cool.gif

Originally Posted by Dianeva

That's an interesting one I've never seen before, thanks for posting. I looked at it for a bit, not understanding what the illusion was. Of course I couldn't stare at it for more than a second before the light felt too bright and I kept scrolling down. Then I realized way embarrassingly late - that was it! Bright light can't emit from a computer screen.

It even seems to be emitted by plain paper - first I thought, it was too simple to post it - but it´s funny, how you can almost not trick yourself out of the avoidance of stuff that gives you blinding sensations.
It does take a while of looking at it to realize this.


One more:



Not really something nobody saw before - but stunning non the less I find - and you don´t have to look it up - I can directly post the thing.

Watch the X in the middle very closely. You should start to see a green dot that rotates around the circle - this dot is an illusion; then you should see see the purple dots disappear.... but they haven't really gone. It is an after image effect, sometimes called a 'negative retinal afterimage' - move your head slightly, and the dots will reappear...