Here’s a new item for our category of soap bubble pictures. The movie shows a science-centre-style demo, not of a bubble, but of a soap sheet. It’s a way of showing patterns like the ones that appear on bubbles, but streaming down a huge sheet. The quality of the movie is not great, so here’s a still photo that shows the effect.
I think this was originally a Victorian demonstration, but I don’t have chapter and verse for that. It’s a demo you sometimes see in hands-on Science Centres, but often it’s not set up so that you can really see the colours. For that there has to be a black background to the sheet, and a translucent screen, at an angle of forty five degrees to the sheet, brightly illuminating it.
I’m fascinated by patterns like these. Just setting patterns in motion, as in many screen savers, doesn’t seem to me to produce effects that are as beautiful. I don’t think it’s just the colours. If we could characterise what makes these patterns special, might we then open up a whole new world of visual expression, using computer animation? Or would we just end up with a small repertoire of pretty effects?
Fancy trying to set up your own soap sheet? It’s not so hard.
The dome in the left hand picture is an illusion! It was painted on the ceiling of the Jesuit church in Vienna by Andrea Pozzo a bit over three hundred years ago. Seen from just the viewpoint of the photo on the left, it’s one of the classics of trompe l’oeil painting. The right hand photo, looking the other way down the nave of the church, shows how Pozzo had to distort his painting of the dome, in order for the perspective illusion to work from a viewpoint near the high altar of the church, as in the left hand photo. (Copyright might be asserted in these images. Most of the images on this site are my own or out of copyright, and can freely be used for private, non-commercial purposes, but these are third party photos. Apologies, I don’t know who took them).
I’m posting about this painting to draw attention to a fascinating recent book in which Pozzo is featured. The effect of his paintings, especially in this church and in the Church of Sant’Ignazio in Rome, is almost magically illusionistic, and the book is about what conjuring and magic have to teach us about perception and the brain. It’s by cognitive scientists Stephen Macknik, Susana Martinez-Conde, with science writer Sandra Blakeslee: Sleights of Mind: what the neuroscience of magic reveals about our brains.The connection between illusions and conjuring has intrigued many researchers, but this is a ground-breaking published study.
Macknik and Martinez-Conde (a married couple, each running a separate research lab) also founded the Best Illusion of the Year Competition, now in it’s seventh year.
Make whatever sacrifice you have to, but unless you were in Washington last Autumn and caught the National Gallery of Art’s exhibition of the work of Arcimboldo there, seize any chance to travel to Milan, Italy, and see it there from January 27th to May 8th 2011. It’s coming on at the Palazzo Reale. Arcimboldo was born in Milan, but became an unrivalled magician at ambiguous images, working four hundred years ago, mostly at the dazzling court of the Emperor Rudolph in Prague. This is his painting of Summer, usually in the Louvre in Paris, and one of a set of paintings of the four seasons.
There’s still a movie about Arcimboldo, available in various formats, to the right on the Washington National Gallery’s website for the show, along with details of a huge sculpture that was in the Washington show, of the painting Winter from the same series of the seasons, by film-maker and sculptor Philip Haas.
We know Arcimboldo didn’t invent this kind of image, if only because of a rather naughty example on a 450 year old dish in the Ashmolean Museum. But he inspired many of the generations of artists, and later psychologists, working with the ambiguous images that you can see in our Ambiguous Images category.
A few weeks back the site got a load of US visitors from a link from a discussion on Reddit. Someone got caught out illegally downloading at college, and as a punishment had to produce a poster about the evils of pirating. The poster was to be inspected by the authorities and if approved, prominently displayed. So the reluctant poster artist put out a query: how can you do a poster that seems to say one thing, but when you look again says something very different. Whatever your take on piracy, (there is a vigorous exchange on the reddit site), the poster problem is an interesting one. I mean, any of us might need to do a subversive poster someday. Someone responded that pixelation might be a way to do it, and linked to our pixelation post.
I reckon that would in practice be a really hard way to do it. Maybe a better way would be by using word combinations that are figure/ground ambiguous, like the Truth/Lies combination shown. It would still be mighty risky though, if your effort was to be inspected, because it’s hard to tweak the ambiguity just so, leaving the subversive message hidden – but not invisible. I tried a couple of tweaks above, trying to get a balanced result at top, to push out Truth in the middle, and Lies below. I haven’t managed to get the recessive message hidden enough yet – not if my freedom depended on it – but maybe you can do better.
One of our most popular images seems to be the 80 illusions poster. For everyone wanting a giant version, there’s been one available 35 x 23 inches, on our selling site at www.cafepress.com/optoct. I was pleased with the quality of the printing when I got one. Because of the interest, we’ve now reformatted the layout for a smaller version available on the same Cafepress site, 16 x 20 inches. Both versions have discreet identification under each illusion, so that they can be followed up on this or other sites. They include little known or novel versions of many famous illusions – and one or two illusions that we think are new.
I was in a Picasso show recently and noticed the head of a portrait sculpture apparently turning to follow me as I walked past. More on the Picasso later, the movie above is my reconstruction of the effect, using the head of the emperor Augustus (I think). It’s not done by animation. You can set up a static image of your own head at home, and it will apparently turn to follow you as you walk past, not just with the eyes, but with the whole face. Just imagine what a comfort that could be for your partner – to have your head always keeping an eye on things whenever you can’t be home yourself.
All you need is to print out a photo of yourself, between a three quarter and a full face view, and then fasten it into a concave shape. I made my concave shape out of a cheap food container, made of some kind of not too hard polymer, so that I could cut it. As you can see below, I just added a little convex wing at one edge, so that the shape is not all concave, but a bit serpentine. When I fixed the trimmed photo in the shape, that makes the face concave, but the ear convex. I reckon the effect works better overall like that, but you might get better results with a bit of experiment.
The real life version will work best if you view it with only one eye as you pass by, or see it from a distance. That’s because to see the illusion your brain has to overcome the cues telling it the photo is concave, so that you see the face the way the brain insists all faces ought to be, convex. But then the perspective transformation of the image as you move past is all wrong for a convex shape, and the face only makes sense if seen as rotating. The effect is related to the Ames Window, and the hollow face illusion. There’s also a really good YouTube demo using a dragon head. (Actually, I’ve only just discovered that, and it’s better than my demo, but don’t tell anyone).
I think Picasso may have been the first person to discover this effect, in 1954.
Here’s an image of a dawn bubble to celebrate the arrival of autumn, and to add to our category of soap bubble images. Or if you’d like to make your own soap bubble pictures, you can go straight to how I made mine.
I’ve not been posting much because I’ve been struggling with a mammoth revision of my technical site on the Poggendorff illusion. But now that’s done, here’s a post on another Poggendorff puzzle.
In earlier posts I’ve shown examples of competition between illusions, and included a demo of a paradox when the Poggendorff and Muller-Lyer illusions go head to head. Bottom left above I’ve shown that last demo again – not so pretty, but I think a clearer demo. Thanks to the Muller-Lyer illusion the outward pointing arrowheads appear closer together than the inward pointing ones, when objectively the arrow points are identical distances apart (note the reference lines in the middle of the figure). But at the same time, thanks to the Poggendorff illusion, at the left end of the figure the arms of the same arrowheads, objectively aligned, would have had to move further apart, not nearer, in order to produce the effect of misalignment that we see. So the two illusions seem to coexist in total opposition to one another, without a qualm. I’ve repeated the arrowheads to the lower right, to show that, at least as I see it, their appearance is just the same as when embedded in the Poggendorff figure.
But then the top figures show that both these illusions can be inhibited, when set in competition with other illusions. Top left the Poggendorff illusion is normal to the left, but cancelled to the right (or is it even reversed?) when the test arms are illusorily rotated by the addition of some Cafe Wall characteristics. And top right, there’s much less difference (again to my eye) between the illusorily lengthened and shortened elements of the Muller Lyer illusion when we see them in the context of a Ponzo illusion (a scene in apparent depth) than as we see them isolated below the Ponzo scene. In the Ponzo scene, the size-constancy effect is increasing the size of the smaller Muller-Lyer element.
So why are the Poggendorff and Muller-Lyer illusions sometimes inhibited when set in competition with other illusions, when at other times they co-exist with rivals in glorious paradox? Any ideas?
You’re going to have to hurry, but if you can get to the Royal Cornwall Museum in Truro, England, before July 3rd, you can see this brilliant sculpture of a dog by British sculptor David Kemp, in his exhibition The Botallack Hoard. It’s one of the dogs in his piece The Hounds of Geevor, and if you don’t make the show, you can see them anytime in bronze in the centre of the nearby town of Redruth. Truro and Redruth are in Cornwall, which if you look at a map of England is the pointy bit in the bottom left hand corner. David lives pretty much as far down the bottom corner as you can go, and I think he’s one of the very best sculptors anywhere working, amongst other interests, on ambiguous images, on which I’ve posted several times before. He works with every kind of what some people might call junk, but he discovers in it ideas that I find very funny and very beautiful. If you’d like more information on David Kemp, see his brilliant website.
Here’s another of David’s sculptures, of three musicians, along with more detail of one of them.
