Thursday, November 3, 2011
Paul R. Laska
The human eye is complex and often mysterious. We “see” when our brain perceives what our eyes deliver. At times, a photograph won’t capture what we thought we saw. At other times we’re unable to see what’s really there.
The eye is also a delicate organ. We all know not to look directly at the sun because the intensity can severely damage our optical system. Various wavelengths, especially in the ultraviolet spectrum, can cause significant damage.
In photography, filters have long been used to enhance images. Latent print specialists have long used a medium-to-dark-green filter to enhance the purple image visualized by the use of ninhydrin.
When working with forensic light sources, filtration is necessary to enhance the effect of the light in use. With blue and cyan (blue-to-green) lights, an orange filter is used. With green, an orange or red filter is used. While UV doesn’t require filters for viewing, it’s seriously injurious to human eyes. Users of UV light sources should wear clear or yellow goggles designed for UV viewing, with appropriate inhibitors to prevent UV light from reaching and damaging their eyes.
A variety of forensic suppliers offer goggles designed for use with forensic light sources. FoxFury features four models, in orange, yellow, red or clear. Manufactured from a polycarbonate material, these goggles also provide impact protection, which should be a consideration—especially when processing a crime scene in a dilapidated location. At under $15 a pair, they provide economical protection.
In photography, a proper filter is necessary to ensure the camera is able to accurately record the image. Interchangeable lenses for single lens reflex cameras and most bridge cameras have a threaded section ahead of the lens elements; a threaded filter of the correct diameter may be screwed in. Depending upon glass quality, most glass filters may be found new for $10–25. Most photo shops also have bins of used filters. If you can find the correct size in the needed color, and find it to have no damage (scratches, fogging or fungal growth), save yourself the money and buy used.
Some bridge and all-pocket cameras lack threaded filter rings. Also, if a variety of lenses with different filter diameters are in use, equipping them may become expensive. Cokin, a French filter manufacturer, offers a convenient solution. Manufacturing a wide range of plastic filters in an extensive assortment of colors and effects, they also make adapters. Some screw into the camera’s tripod socket and hold filters in front of the lens. Others use a threaded adapter for a specific diameter lens. One mount consists of a spring that clamps to the front element of the lens. The Cokin system provides solutions to a variety of problems facing the filter-using photographer. For more information, visit www.omegasatter.com