Forensic Dentistry, Second Edition

226 Forensic dentistry

results in nonvisible light photography will require some trial-and-error

experimentation. Available and predictable sources of nonvisible lighting are

listed below for both ultraviolet and infrared photography. This list is by no

means totally inclusive and is intended to be a potential resource. It is possible

to find sources of adequate nonvisible light other than those listed here.

11.10.1 Ultraviolet (UV) Light Sources

•   Sunlight: A good source of long-wave UV light but not practical for

situations requiring indoor or nighttime exposures.^24

•    Fluorescent tubes: Produced in short, medium, and long UV wave-

lengths, these are routinely used for indoor lighting; some useful UV

emission. One of these types of lights is known as a black light, which

emits good UV radiation; the brighter, the better.

•   Mercury vapor lights: Particularly useful in lighting small areas with

intense UV light. Problems include long warm-up time for the light

and limited availability.^24

•    Flash units: Many older units provide adequate UV light emission.

Some newer units emit a measurable amount of UV but will require

experimentation to determine the correct output.^24

•    Combination fluorescent/black light: This light combines the emis-

sion of the two light sources in one light fixture; commonly known

as a Wood’s lamp.

•   Special wavelength UV LED lights^37 (Figures 11.28 and 11.29).

11.10.2 Infrared (IR) Light Sources

•   Flash units: Most commercial flash units emit sufficient IR light to

be adequate but require experimentation to determine their accept-

ability in infrared photography.

•   Tungsten lamps: Used routinely in forensic investigation. The brighter

the Kelvin value, generally the more IR output.

•   Quartz-halogen lamps: Good source of IR radiation if unfiltered;

more readily available and easy to use.

•   Special wavelength IR LED lights.^37

11.11 Focus Shift

After securing a source of predictable nonvisible light illumination, the prob-

lem of focus shift must be addressed. By definition, focus shift is “the dis-

tance between the visible focus and either the infrared or ultraviolet focus.”^17