Tuesday, 27 April 2010

Marvellous Optical Illusions

Question: What is an optical illusion?
Answer: It is an optical phenomenon resulting in false visual impressions

Firstly, I think that the definition above doesn't even scratch the surface of the complexity of illusions, and secondly, I reckon that optical illusions are intrinsically fascinating for two reasons: (1) because they produce something that is not as it seems, which in turn makes us challenge 'face-value'; and (2) most of them are master-classes in physics and psychology (in varying degrees).

If that wasn't enough to establish the credibility of optical illusions, Bristol University actually has a 'Professor of Illusions'. Oh yeh. This is serious stuff.

"So!" I hear you cry, "what on earth has made you start banging on about optical illusions?"

Well, I was listening to the radio today when I heard a discussion on the subject, and (being the saintly soul that I am), I decided to have a scout around to find some gems to keep you entertained.

Vid.No.1. How cool is this?! Imagine the maths that went into calculating the perspective

Pic.No.1. It looks like moving waves doesn't it? I can assure you that this picture is completely still - see, just touch it (ha ha, just teasing)

Pic.No.2. This illusion is actually a chalk drawing on the pavement - a true anamorphic picture

Pic.No.3. This is what Pic.No.2 looks like when viewed at another angle (do you fancy calculating the perspective on that? Yeh, me too)

Pic.No.4. Another anamorphic picture, also drawn on the pavement. Bloody amazingly talented.

Pic.No.5. Frisbee optical illusion

The optical illusion above, apparently came about entirely by chance. Have a look at the picture, and in particular the two frisbees that you can see. Initially you might think that the picture has captured a moment when both frisbees are in the air. But that is not the case. Only one frisbee is actually airbourne.

The black frisbee is in the air, and the yellow one is on the grass. But the photographer has captured the moment when the shadow of the black frisbee is in just the right place to convince us that it is the shadow of the yellow frisbee, and that the yellow frisbee is actually in the air. How cool?

Pic.No. 6. Expanding Star

The pattern above is stationary – yet it seems to expand, especially if you don't look directly at it, for instance when reading this text. But here is a bizarre fact. There is a percentage of the population for whom these illusions don't work...... that isn't logical surely?

 Pic.No.7. Chequer Board

And now for my last offering. If you look at the chequer board above, it looks like the centre is bulging. Not so! Every single one of the large black and white squares is of the same size and proportion. At first I didn't believe it either, so I got a ruler and held the straight-edge up at the screen (that's what I call technological advancement), and lo and behold, they are all the same size.

Crikey. Isn't a bit of 'random digressing' fun? Has anyone got any interesting optical illusions to add to the melee?


  1. Oh, Dear Anne!

    If you are not a child of the 60s, you have surely brought back haunting memories of that period:) Great post, and as soon as my siezures subside, I will read it again.

    :) Thanks, Ron

  2. Shite Ron, I hope the seizures subside. Maybe I should put a warning on the post...?

  3. Dear sweet Anne,

    I am okay...I just need to remember not to listen to Jimi Hendrix at a volume near the threshold of pain while viewing optical illusions.

    As an aside, I played a blank audio tape full volume last night, and the mime next door went NUTS!

    Just saying,
    Be well - Ron

  4. I LOVE IT!!! I have always loved optical illusions. I'll forward some after I track them down. Thanks for the awesome diversion.

  5. Ok. Here's one of my favorites!!! I see the girl going in both directions alternately. It changes without warning. Grrrr. I can NOT figure it out. I hope you enjoy it!


  6. That's ace Heather! What were you? Left brain or right brain? I was left brain and I was a bit disppointed because it said most people were left brain.

  7. That's great, the chalk drawings are totally amazing!

    My eyes hurt... total coincidence, I am sure...

  8. That was fun!.. Thanks for sharing. I love seeing optical illusions like the dragon in person. They are so trippy.

  9. Some good ones there. I liked the Batman one especially, as I haven't seen that one before. Some of these chalk pavement artists are incredible.

    I haven't got an optical illusion for you, but if you go to


    you can see the optical delusion that is your unreadable website, when viewed on bloody awful IE 6... which they insist on using at my place of work.

    I think they purposely won't upgrade to stop us surfing the internets at lunchtime.

  10. What are you trying to do to me? I was anticipating a peaceful, soporific half-hour on the blogs before I went to bed .... now I'm buzzing like a pylon.


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