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Author Topic: Benham's wheel illusion  (Read 9832 times)

silvertop

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Benham's wheel illusion
« on: August 14, 2010, 06:50:30 AM »

Note admin: as this is spintop related I split the topic from the illusions thread on the nstr board

Since this is a spinning top forum, how about a spinning illusion - Benham's Wheel, or Benham's Disc.  A spinning black and white image actually gives the illusion of colors when spinning at the proper rate.  We made thousands of Benham's wheel tops at The Toycrafter.  The right speed, lighting, etc. can give quite vivid red, green, and yellow colors.  The computer version gives a sort of dull reddish brown. Oddly, while the official graphic is a black semicircle with the other half occupied with broken rings of black, you can get at least a partial effect by just cutting a disc of newspaper print, etc. and spinning it.

My favorite thing about this illusion is that the optics-medical-brain folks have actually declared this illusion to be a "mystery", and no longer worthy of actual study.  Despite many "explanations" that can be found on the web and elsewhere, this illusion has been banned as a topic of inquiry for Doctoral Theses, scientific papers, etc.  There just does not seem to be any "reason" for this illusion.

Click here for a computerized spinning version  http://www.michaelbach.de/ot/col_benham/index.html
« Last Edit: August 19, 2010, 09:43:47 AM by ta0 »
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Don Olney
1237 E. Main St.
Rochester, NY 14609
topman@rochester.rr.com

ex-ToyCrafter

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Re: Re: Optical Illusions
« Reply #1 on: August 17, 2010, 05:33:20 PM »

"Why didn't i think of asking people to put they're own optical illusion!"

I'm glad you asked.
(that gust of hot air you feel, is the summer breze, not me blowing my own horn)

I designed a TOPical optical effect for Silvertop, that is now being used by Sylvania and Motorola to sell people new lights.

I could never see the colors in Benham's wheel. (i'm not color blind, but i can't see the colors in stars, either (shrug))
And there I was printing Benhams' by the gross.
I figured i could do better, but i also knew Silvertop would never give-up on Benham's.
On the other hand our Color Wheel was pretty tame ('red and blue rings make purple'),
so i talked him into letting me upgrade the Color Wheel.

I can't find a copy of the old color wheel, This is my upgrade.


My Color Wheel ("Zonker's Wheel") is based on the the fact that, at that time,  fluorescent lights strobed at 120 cycles per second, right along with the AC power.
When spun under 'strobbing' fluorescent light, the pattern does the 'wagon wheel'  effect., where the rings seem to turn, some with, some against the spin. And as
the top slows, one by one, the rings will seem to slow, stop, and reverse direction.  ...and it still makes purple.

I don't know how Sylvania and Motorola got ahold of it, but it don't belong to me anymore, anyway. (shrug)
They use my design on white plastic tops as a "flicker Checker"
They want you to trade in your old magnetic ballasts for new improved  electronic ballasts, that cycle faster (or something) so that the fluorescent gas doesn't have a
chance to cool down, or flicker.
So, if the "flicker checker' works for you - you're old-fashoned.
(can you tell i'm bitter that it's not known as Zonker's Wheel?)

Explination from Wikipedia:
http://en.wikipedia.org/wiki/Fluorescent_lamp#Flicker_problems
"Fluorescent lamps using a magnetic mains frequency ballast do not give out a steady light; instead, they flicker at twice the supply frequency. This results in
fluctuations not only with light output but color temperature as well,... a stroboscopic effect can be noticed, where something spinning at just the right speed may
appear stationary if illuminated solely by a fluorescent lamp.... Unlike a true strobe lamp, the light level drops in appreciable time and so substantial "blurring" of the
moving part would be evident."..."Fluorescent lamps using high-frequency electronic ballasts do not produce visible light flicker, since above about 5 kHz, the excited
electron state half-life is longer than a half cycle, and light production becomes continuous."
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ta0

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Re: Benham's wheel illusion
« Reply #2 on: August 19, 2010, 09:42:51 AM »

I first learned about this illusion through one the Toycrafter Benham's disks and it has always fascinated me. It is also known as the Fechner Phenomenon.  Comparing what I see with what friends describe I realized I see different colors on the wheel in different order than them. I am slightly "color blind" (I never noticed until I took an Ishihara test in my thirties) or at least I perceive colors slightly differently, so these facts may be related.

Zonker: I have one of those flicker tops from Motorola and I always thought that Toycrafter have gotten the idea from them (or an earlier version) and not vice-versa.  Congrats on the invention, that is an interesting story. Maybe you should autograph the one you are selling on ebay!
« Last Edit: August 19, 2010, 09:45:05 AM by ta0 »
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pplgrande

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Re: Benham's wheel illusion
« Reply #3 on: August 20, 2010, 01:01:01 AM »

Thats really neat and creative, we should find a way to incorporate that illusion on the top of a trompo
I've been trying to find some kind of illusion that would show an image rather than different colors when it spins, when I spin my Gusy trompo the top of it looks amazing, it has a hologram on the top and when the light hits it looks very nice and if I tilt it the right way I think I can see the little guy thats drawn on the top
Check it out

My camera is not that good as you all can see, but you get the idea
« Last Edit: August 20, 2010, 01:08:54 AM by pplgrande »
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pplgrande

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Re: Benham's wheel illusion
« Reply #4 on: August 20, 2010, 01:02:02 AM »

Gusy Trompo
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pplgrande

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Re: Benham's wheel illusion
« Reply #5 on: August 20, 2010, 01:04:13 AM »

....
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pplgrande

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Re: Benham's wheel illusion
« Reply #6 on: August 20, 2010, 01:05:31 AM »

And spinning
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pplgrande

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Re: Benham's wheel illusion
« Reply #7 on: August 20, 2010, 01:07:26 AM »

........
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silvertop

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Re: Benham's wheel illusion
« Reply #8 on: August 22, 2010, 04:42:25 PM »

The Benham's Wheel illusion is only effective at lower speeds.... a throwing type top would fall down long before any colors would show up. A color mixing graphic would work nicely.  I think the "flicker" part of the illusion would also not appear until the top had slowed down enough to fall, but it would be nice to try.   
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ta0

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Re: Benham's wheel illusion
« Reply #9 on: August 22, 2010, 05:36:06 PM »

Omar, what you discovered on the hologram of the Gusy trompo was an idea I had years ago: make a hologram so a static image appears even when it is spinning very fast. I works because only when the disk is oriented correctly with respect to the light source and yourself the image materializes and most holograms will work that way.  I even did a patent search, as I thought there could be a market much larger than tops: wheel hubcaps. Unfortunately, I found that Hughes had already got a patent 15 years before and the applications they mentioned where hubcaps and vinyl records.  I still have an idea for a variation that could be interesting for fingertops and one day I may pursue it.

At the time I had the idea I was making as a hobby (awful quality) holograms. I don't recall if it was before or after that time that I got some of the best examples of spintops with holograms anywhere (I wasn't into tops yet so my interest was in the optical effect). The tops are actually those 4 or 5 inch disks with a dimple in the center that  came with beautiful geometric holograms on top. But a guy took some limited edition comics holograms and put them on top. The two I have feature Spiderman. In one Spiderman starts with his hands in the ground and stands up while the disk makes a full rotation. In the other the guy starts dressed in a suit and transforms to Spiderman at the end of the rotation. There is a very famous early hologram with the same effect in which a woman seen from the back seems to be flashing her naked body but as you turn around the hologram she closes her arms and covers herself to your disappointment  ::) I saw the original at the New York museum of holography before they closed.
« Last Edit: August 22, 2010, 05:38:28 PM by ta0 »
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