Optical Illusions

Hundred-year-plus puzzles

david — Tue, 01 May 2012 08:42:09 +0000

I remember being baffled by the illusion to the left when I was a child. I think it was the first illusion I saw. The upper and lower blades are identical, but the lower one looks a lot larger. It’s called the Jastrow illusion, and it’s not surprising I was amazed by it, because it’s [...]

Back-yard Poggendorff

david — Sun, 01 Apr 2012 17:25:55 +0000

This is another demo to see whether it’s true, as has often been claimed, that the Poggendorff illusion is much weaker when it’s seen in three dimensions. To my eye, it’s not true: in this lash-up of bits and pieces in my back yard, the illusion is still strong: the long rod is straight [...]

Muller-Lyer paradox (amended post)

david — Fri, 02 Mar 2012 19:30:57 +0000

Here’s a new way of looking at the Muller-Lyer illusion – a way that presents a paradox. In the Muller-Lyer illusion, a line segment ending with outward pointing arrowheads looks shorter than an identical segment ending with inward pointing arrowheads. So in this version, whenever the arrowheads are visible, the [...]

Native Canadian Ambiguous Art

david — Tue, 31 Jan 2012 17:14:26 +0000

Depending how you see it, this panel either shows two killer whales looking at one another in profile, or a bear looking at you head on – the killer whales’ fins top centre become the bears’ ears. And then the killer whales’ tails centre bottom become the mouth of a third creature, probably a frog, [...]

Cheating with tessellations

david — Tue, 03 Jan 2012 22:05:35 +0000

Tessellations are patterns whose repeat motifs fit together like jig-saw pieces, with no gaps and no repeats. For an introduction, see our earlier animation. They can be abstract patterns, but the most intriguing are the ones devised by tessellation maestro M.C.Escher in the middle of the last century, which show representational motifs, such as animals, [...]

Hybrid Portraits

david — Fri, 25 Nov 2011 17:40:37 +0000

Hybrid portraits superimpose one portrait on top of another, so that one appears with close viewing, and the other emerges with more distant viewing. Or with reduced image size. Or just by taking off your specs, if you are just a little way away and are seriously short-sighted. Whatever works for you, here Charlie Chaplin becomes [...]

Bubble Beach Penguin

david — Thu, 27 Oct 2011 16:51:22 +0000

Here’s another picture to add to our category of soap bubble imagery. For details about how I photograph the bubbles, see entries in the soap bubble category. I hadn’t noticed before that there are some great movies of bubbles on Youtube, such as this model of Jupiter’s turbulence, or this movie of a bubble bursting. [...]

Magic Ring

david — Tue, 27 Sep 2011 07:25:47 +0000

Here’s a movie of a brilliant, double spiral novelty illusion ring. It’s available to buy from Grand Illusions, and on that link you can also see another movie of the illusory effect. As the ring is rotated, it seems to expand when rotated one way, and contract when rotated the other [...]

Decor with Attitude

david — Mon, 05 Sep 2011 09:17:31 +0000

This is an installation called Zig-Zag Corridor by Czech artist Petr Kvicala, in the Dox art centre in Prague, Czech Republic. He’s an artist who produces dazzling patterned effects. In this one, beautiful diagonals meander through the patterns, although the linework is entirely made up of a continuous sequence of horizontal and vertical segments. However, [...]

Hidden Message

david — Wed, 03 Aug 2011 14:49:25 +0000

Can you read the message encoded in the image? A few months back I posted about embedding hidden messages in images. Since then I’ve come across a much better way of doing it, using the lettering in the image above. Lettering? What lettering? You may not even have been able to spot the lettering [...]