Lighting

The normal rules of lighting apply to reflected ultraviolet photography. For flat subjects such as gels, chromatograms, documents, etc., 45° "copy" lighting is advocated. When photographing the human skin the source of radiation may need to be moved to reduce highlight reflections to a minimum. The oils in human skin reflect ultraviolet very efficiently, so large areas of bright highlight may obscure important pigmentary detail (Figure 24). When using an ultraviolet transmission filter over the camera lens it is possible to work with the visible modelling lights built into most studio flashes. If the flashgun has no modelling light, or is filtered with the Wood's filter, it is preferable to attach an electric torch to the top of the unit - this will help in placing the highlights appropriately. Continuous sources of ultraviolet "leak" enough blue light for them to be positioned by eye, but again remember the warning about erythema and conjunctivitis discussed above.

Figure 24 (above). The oils in human skin reflect ultraviolet very efficiently, so large areas of bright highlight may obscure important pigmentary detail.