Our light painting workshop explores the science behind photography by looking at the electromagnetic spectrum and how we can use it.
(not a Bond film)
Visible light can be split up into a spectrum of colours.
A rainbow forms when white light is split up when it passes through droplets of rain. The light changes direction as it enters and leaves the water droplet – refraction (GCSE Bitesize link) – with the amount of bending depending on the wavelength of the light. The white light spectrum, from blue to red, is split up over different angles. You can see a similar effect if you shine a beam of white light through a triangular prism.
In our workshop we look at the spectra of different types of light sources and discuss why they are different. We make our spectra using a slightly different method, with diffraction gratings, and we use a range of emission tubes to view the spectra from different types of light source. This is very similar to how researchers work out what distant stars are made out of.
However, visible light is just a small part of the electromagnetic spectrum.
Infrared radiation and ultraviolet radiation are also electromagnetic waves. They are not detected by our eyes, but can still be very useful to us. Infrared radiation can penetrate some things that visible light cannot, so using an infrared camera we can see things that would otherwise be hidden:
One good example is using a thermal imaging camera to look for hot things (like a person) through material that would be opaque to our naked eye, like debris in a collapsed building or, in this case, a bin bag:
In a thermal image like this, the bright yellow areas are hottest and the dark blue areas coldest.
This idea is hugely important in astronomy, where clouds of dust and gas often prevent visible wavelengths from reaching us from distant objects. Infra-red astronomy, however, can reveal stunning detail and structure which has huge implications for our understanding of the universe.
The Trapezium cluster in the Orion Nebula, from the Hubble Space Telescope. On the left, visible light; on the right, an infrared picture reveals a swarm of stars and brown dwarfs.
A modern camera and the human eye work in similar ways, with even the structure of the eye relating to the parts of a camera; the lens, aperture (iris) and detector (retina). In the workshop, we look at some simple pinhole cameras and lenses before having a go at light painting.
Light painting is done by keeping the shutter of the camera open for a long time – somewhere between 5 and 10 seconds, or even longer. Any movement that occurs while the shutter is open will appear as streaks across the photograph. So by taking the picture in a dark room and using bright LED lights, we can create all sorts of shapes, shadows, spooky figures and colourful concoctions.
To the left, one of the pictures taken in a light painting workshop by our friends at the Centre for Life.
The pictures below were taken by Think Physics’ film-maker Jonathan at an arts event called Ghost Peloton, which consisted of dozens of illuminated cyclists. It was staged in Leeds to mark the Yorkshire Grand Départ, the opening of the Tour de France in 2014.
Combine light painting techniques and stop-motion animation, and you can (with a huge amount of patience) produce something more like this:
If that looks like too much effort, you can automate the process to some extent using a phone or tablet app. One example is Holographium.
…but things are about to get easier. A company called Pixelstick have created a way to insert pictures and graphics into photos. They can even make time-lapse videos of moving images. The Pixelstick flashes up different sequences of light and as it moves in front of the camera they appear like a fully formed image. By taking a series of photos you can put them all together to make some amazing animations.
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