Thursday, 1 September 2011

Putting things in perspective

Today's picture is not from Vršovice at all, but from Holešovice in Prague 7. That's just about as far as we have ever ventured in these pages - but there's a good reason for the journey. Today is theme day on City Daily Photo, a splendid website which aggregates photo diaries from all over the world and publishes the main pictures side by side, so you can see what's going on pretty much anywhere at a glance. And the theme for September is 'Perspective'.

A few weeks ago I paid my first, long overdue, visit to Dox, the newest - and one of the most successful - of Prague's contemporary art galleries. Here we can see 'Zig Zag Corridor' by op-artist Petr Kvíčala, an unbroken 10cm-wide red line painted directly on the walls of the gallery. The idea is that when viewed end-on, the rectangular lines start to reveal diagonal 'zig-zag' paths, which emerge in a ghostly way from the design. But to me there's a further illusion. Can you see how despite the straightness of all the lines, the walls of the corridor appear to curve or bulge out slightly? Only one person could answer my query, my friend David, a specialist in optical illusions. He told me what was going on:

'It's the Hering illusion, a special case of the more general Zollner illusion. In both, the short cross lines usually extend either side of the long lines that seem to bulge or lean over, but, as here, the effect works even if an edge just abuts an array of short obliques.  Amazingly, it was first reported in the edges of the feathers of arrows by Montaigne.' So, now you know!

Click here to view thumbnails for all participants in today's City Daily Photo theme day. Or, for more optical illusions, please visit David's site here. And now I'm feeling just a bit dizzy, so I'm off for a beer to set things straight again.

8 comments:

J Bar said...

Marvellous shot.

Leif Hagen said...

An interesting, eye tricking perspective! Fun twist on theme day!
Regards from EAGAN daily photo

Jilly said...

Well... not only is the photo fabulous but the explanation of the bulge too. Clever stuff, Alex x

nathalie (Avignon) said...

Clever and well explained. Great take on today's theme.

Gemma Wiseman said...

Incredible sight! Amazing optical illusion!

Kay said...

Outstanding photo of a very interesting piece of art. And thank you for the explanation. Salud!

Mo said...

Wow wouldn't like to be feeling unwell here. Great choice for the theme

Seoman said...

Great photo on a wonderful blog

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