Ultraviolet, Infrared & Fluorescence Photography

The electromagnetic spectrum is comprised of a series of waves arranged in order of wavelength. The various types of radiation forming this spectrum differ widely, and only a very minute part of this spectrum has any relevance to photography. Usually photography is confined to the visible part of the spectrum, those waves that the eyes see as "light'. This part of the spectrum is comprised of wavelengths from approximately 400 700 nanometers (nm), which can be seen by the eye as a change of color. The shorter wavelengths are blue, the longer ones red. At either end of the visible spectrum lie two "invisible" spectra: the ultraviolet which extends from x-rays to the blue end of the visible spectrum, and the infrared which extends beyond the red and into heat (Figure 1). One important function of photography is to extend the range of spectral visualization of the human eye and record these "invisible" spectra. Infrared and ultraviolet photography therefore acts as investigative tools that are capable of discovering new facts about the subject. In some fields of investigation, extensive work has been reported on the use of invisible radiation photography. Other areas of application, however, remain unexplored and await the attention of the research-oriented photographer.