Natural history, wildlife and scientific photographer Adrian Davies shows you how to make the invisible visible
See scientific photography in a new light with Adrian’s UV project
Ultraviolet (UV) fluorescence is the visible light that is emitted from a subject when it is illuminated (the technical term is ‘excited’) by UV in a
dark room. Think of the longwave UV lights used in nightclubs, funfair ghost trains and so on that make shirts glow a brilliant white due to the whitener in the fabric.
Many subjects fluoresce in UV, including some minerals (which can be identified by the colour they produce); security markings on banknotes, passports and driving licences; some plant material (including the quinine in tonic water, fruit and some woods); different birds’ eggs; some animals such as scorpions; and various cosmetics such as face paints. A walk around the garden at night with a UV torch, or in your bathroom, can be an enlightening experience. The technique is also used by forensic scientists and art restorers.
UV fluorescence photography is much easier now than it was before, thanks to the availability of relatively cheap yet powerful UV torches containing LEDs. The technique can yield some startling and unexpected results.
There are several models of UV torch on the market, but you will need a relatively powerful one for photography purposes. My current favourite model is the Convoy S2+ 365nm Nichia UV Waterproof LED Flashlight, which costs around £20. The most useful type is one that emits UV at a wavelength of around 365 nanometers.
For UV fluorescence photography you will need to be in a dark room, so that the only light reaching the subject is the UV from the torch. Virtually any camera and lens can be used, though they must have the ability to shoot long exposures. You will need a lens with a macro or close focusing facility for smaller subjects, a good solid tripod and a remote release.
UV wavelengths from the sun can cause sunburn to the skin, and prolonged exposure to UV can also cause greater damage or even skin cancer – so take great care when using powerful UV torches. In particular, never point them towards someone’ s eyes. If you are photographing teeth or fluorescing face paint, get your model to shut their eyes during the exposure. If you are going to do a lot of this work, it may be well worth getting a pair of UV absorbing safety glasses. (Ski goggles will work too, as these are designed to absorb the UV light wavelengths that can cause snow blindness.)
Take care, too, when working in a dark room. I use a head torch so that I can make adjustments to the camera and subject without having to move around in the dark.