Nat­u­ral his­tory, wildlife and sci­en­tific pho­tog­ra­pher Adrian Davies shows you how to make the in­vis­i­ble vis­i­ble

Digital Camera World - - CONTENTS -

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.

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