Pinhole Perception – Guest Blog from Mediator James Morris

James Morris, a member of our multi-talented Mediator Team here at Science Gallery Dublin tells us about the wonders of the pinhole camera – he can be found on Twitter at @JMorrisj6

It’s understandable why cameras are so popular; they echo the way we look at the world almost exactly.

Pinhole cameras, and the camera obscura effect they reveal, are the historical seeds that bloomed modern photography, and given our ‘pupils’ (eye-holes), are effectively pinholes through which we peer, they also illuminate something unique to us all.

It begins, not with creation of heaven and earth, but with light from the sun or another photon emitting object, like a bulb, or a lad with a firework, striking a scene. Some photons are absorbed by objects in the scene, like sleeping cats, turnip plants, moons, and picnics, causing important features of life like content cats, disappointing dinners, full moons, and warm beers.

However, most light is reflected in all directions, each light beam laden with a lovely cargo containing all the information needed to perceive the image. Some of these light beams find their way being beamed through our eye-holes, or the pin-hole in our pinhole camera, where it is projected onto a dark place, the retina, or the back of a box, respectively.

So far so good, the eye is effectively a pinhole camera.

The piece Seeing Stars by Dianne Bos at SEEING demonstrates the camera obscura effect produced by multiple pin holes, creating a galaxy of light bulbs when viewed from the front.

The photographer Albelardo Morrell is known for his examination of the camera obscura effect. ‘A View of Central Park Looking North – Summer 2008’

But as well as being a very tasty meal for the eye to feast upon, the camera obscura effects shows us something peculiar that must be true of our visual perception too.

"All objects illuminated by the sun will send their images through this aperture and will appear, upside down, on the wall facing the hole.’’

As noted by Leonardo Da Vinci and seen above, images produced by camera obscura are projected upside down. This is owing to the continuation of light rays from the source through the hole onto the wall. The only way the image can be projected is upside-down if the line of light is followed. So seeing as our eyes use the same principles of optics as that which produces the camera obscura, a point that Da Vinci studied in detail (below) that means that there’s a tiny upside-down image of this article being projected onto your retina. If only there was a tiny Albelardo Morrell to take a picture of this projection, maybe this madness could be seen.

It’s then the turn of the 120 million rods, which sense dark and light, and the 6 million cones, which, when functioning well, detect electromagnetic wavelengths of the short, medium, and long wavelength categories (corresponding to the colours blue, green, and red), to absorb the image falling onto the retina, convert it into electricity, and wire it back to the brain via the optic nerve. Then the occipital lobe does a bit of magic and you see a right-way round image focused to varying degrees of ocular capacity in your mind’s eye. Lenses do the job of focusing light on the retina, and if they are off kilter then you get near or shortsightedness which can be tested at Eye Care Works at Science Gallery. 

The world is upside down as we see it through our eyes, and our brain turns it around in real time. Or maybe what we see is correct and up is down, down is up, but that’s very confusing altogether. For Bojana Danilovic, some aspects of her life are seen upside down, so maybe there is a righting system and for most of us it works without hassle, unaware of its crucial existence. 

On the other hand a pinhole producing a camera obscura doesn’t have to worry about nervous wiring and energy conversion and image righting; the back wall simply reflects the light the way it falls. A few thousand years later it was discovered that if a sheet dosed with silver halide was placed where the image is formed, the image of the sleeping cat could be immortalised in photograph. Images and videos can be immortalised in brains as long as they live, but only certain images stick there for life, like pictures of a confident cat failing to jump a ledge, or dinosaur gators stomping about a golf course

Henry David Thoreau may be right to some degree in saying ‘It’s not what you look at that matters, it’s what you see.’, but unless you’re Daniel Kish, who sees using sounds, in terms of visual perception, the eye is the tool that absorbs light from the world, the brain the beholder that sees, and both functioning well, of course, are very necessary for what we call sight. 

SEEING closed in Science Gallery Dublin on Sunday 25th of September. You can take a look back at the show over on the SEEING website, or on YouTube.