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A brief background on ultraviolet radiation
Before attempting to undertake ultraviolet photography, it would be helpful to know a little background of this special kind of scientific photography. Scientists label the light used in normal photography as “visible light" or light waves that are visible to the human eye. This means that there are light waves (more aptly called electromagnetic waves) that are not visible to the eye. One group of these invisible light waves is ultraviolet radiation. Compared to visible light, ultraviolet has more energy and can disrupt human cells. This is why skin doctors warn against overexposure to UV rays. But UV rays are useful in helping the human eye extend its range of vision. Simply put, with the use of ultraviolet radiation in digital photography, the human eye can unveil whatever it was that was previously unseen. This is why ultraviolet photography is used in scientific and medical researches. And this is why special ultraviolet cameras are part of the set of forensic photography equipment.
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Basics of ultraviolet photography
Ultraviolet photography is all about photography lighting because ultraviolet radiation, after all, is of the same nature as visible light. There are two basic techniques to carry out ultraviolet photography using digital cameras: reflected technique and fluorescence technique. In the reflected technique (also called direct technique), the subject is illuminated with ultraviolet light and the camera uses a filter that will allow only the UV light (reflected by the subject) to pass through. In the fluorescence technique, ultraviolet rays are again used to illuminate the subject but the material of the subject responds to UV by glowing or emitting fluorescence. The digital camera captures the image projected by fluorescence. Since ultraviolet images may appear distorted to the human eye, the ultraviolet photographer also needs to take a normal picture of the same subjects using regular digital camera.
Both techniques in ultraviolet photography will require a better and more concentrated source of ultraviolet light than direct sunlight. The popular sources for professional photographers are mercury vapor discharge lamps and xenon arc lamps. The mercury vapor discharge lamps can provide a consistently continuous ultraviolet radiation, which is useful in taking images of documents and other physical inanimate evidences. The xenon arc lamps can also supply continuous ultraviolet light but it can also be used in providing instantaneous and fleeting UV rays. In forensic photography, flash UV is recommended in taking images of patients and living victims. Sometimes, mercury vapor discharge lamps are used in taking images of the skin, but these lamps are fitted with a Woods filter, to restrict the UV radiation.
Becoming an ultraviolet photographer requires a strong interest in science, a passion for accuracy, and a characteristic meticulousness for details. There are numerous digital photography schools that offer courses and workshops for those who are interested in ultraviolet photography.
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Williams, R. & Williams, G. (2002). "Reflected ultraviolet photography." Medical and scientific photography. Retrieved May 23 from http://msp.rmit.edu.au/Article_01/index.html