UV/IR Injury Photography
Written by Curtis Klingle and Katie Reiter   

ROUTINE USE of ultraviolet (UV) and infrared (IR) in forensics and in the medical field is not something that is new. Vast amounts of information on these subjects can be found, but much of it is contradictory. In one article an author would report that a particular technique worked, and in yet another article a different author stated something nearly the polar opposite for virtually the same instance. Apparently what worked for one person didn’t necessarily work for another. There appeared to be too many generalities and too many opinions— and not nearly enough facts. The goal of the authors was to be able to devise a method or methods that anyone (including those with limited photographic experience) could follow and obtain the best results possible, and not churn out yet another boring dissertation on these subjects which would be difficult to understand and with little practical application.

Research and Methods

Light is the most important component of photography. UV and IR photography utilizes what is called light, but is actually radiation waves in the electromagnetic spectrum. To begin, a brief explanation of the electromagnetic spectrum is necessary.

Electromagnetic radiation includes many different forms of radiation. Starting at one end of the continuum, we find gamma rays, which are closely followed by X-rays. Ultraviolet is next. And then comes visible light, which precedes infrared. Infrared is then followed by microwave and radio waves. The unit of measurement used in the spectrum is termed a nanometer (nm) which equates to one billionth of a meter. Ultraviolet radiation ranges from 10nm to 310nm, visible light 400nm to 700nm, and infrared 710nm to 1,000,000nm.

For the purposes of UV and IR photography, the waves we are interested in are those in the 310nm to 830nm range. Basically, there is the light (or radiation) that you can see (400nm to 700nm) and the light that you can’t see (anything above 700nm).

One of the most informative books on the subject of injury documentation is the 2004 publication by Robert B.J. Dorion, Bite Mark Evidence. In this book, the author painstakingly documented procedures and equipment that are necessary to document a victim’s injuries. According to Dorion, light waves begin to penetrate the surface of the skin starting around 200nm and gradually increase in the depth of penetration (up to 3 mm) as you go further up the infrared spectrum, peaking at 790nm. The depth of penetration then begins to decrease as one goes higher in the IR spectrum. Because UV and IR penetrate the skin, they can be invaluable tools in detecting injuries that otherwise may not be visible on the surface of the skin.

UV and IR photography are useful tools in photographically documenting injuries because of the biological and biochemical changes that occur when a body is injured. Specifically, in contusions and bruises, the skin remains unbroken while small blood vessels rupture in the underlying tissue. This escape of blood into the tissue results in the familiar discoloration of a bruise. Hemoglobin, melanin, and bilirubin collect at the injury site and appear as dark areas, thereby creating contrast between normal and damaged tissue.

Although a bruise may be visible to the naked eye, when viewed under UV, the injury will be enhanced showing otherwise hidden detail. However, the same bruise may actually “disappear” when viewed or photographed with IR. It is very important to always remember that IR penetrates deeper into the skin. If the injury is merely epidermal or dermal, it may not be completely visible in IR photography. It is often suggested that IR is “the way” to capture bruises. This statement is false. Unless the injury is deep—such as a severe bruise, bite wound, knife wound, or gunshot wound—IR will not capture the full extent of the injuries.

Prior to digital imaging, UV and IR photography were accomplished with film cameras. Both techniques were very time consuming and expensive. The advent of digital cameras has made this process faster and much less expensive. Instead of film, a digital camera is equipped with a charge-coupled device (CCD). For a very simplified explanation, the CCD acts like the film in the camera. When the shutter is opened, the CCD collects the incoming light and converts it into a charge, which is then converted into an image. Most digital cameras, however, have filtering devices built in to inhibit the passage of UV and IR. In order to perform UV or IR photography, the camera utilized must allow the passage and capturing of this “light.” The camera manufacturer can be contacted and an inquiry made as to whether the camera can be utilized in UV or IR photography. You can also test the camera as suggested in the sidebar “Testing the Equipment”.

Getting started with
ultraviolet photography

Accessibility to an alternate light source (ALS) with variable light frequencies is a necessity in injury examination and documentation. When examining a victim, an ALS that emits light in the 450nm range will be needed; this is the optimum light frequency to view and enhance injuries, though some lower frequencies can and should also be utilized. Technically, 450nm falls within the visible light spectrum. However, all research revealed that the term ultra-violet is commonly applied to ALS in this wavelength. (Note: When using an alternate light source, be sure that safety goggles are worn by the operator and the person being examined. The light frequency dictates which color of goggles will be utilized.)

Before documenting the injury with an ALS, do a quick examination and take note of any visible injuries. When this preliminary examination is completed, the next step is photographic documentation. First, it is necessary to photograph the victim’s face for identification purposes. Any injuries that were observed during the preliminary examination should now be photo-graphed with and without a scale, in full color, and at the standard camera settings. Extensive notes should be taken of all injuries and their locations. Be sure to wear appropriate personal protective equipment when working with injured individuals.

To perform ultraviolet photography, the camera should be set to black-and-white with a slow film-speed setting, preferably ISO 100 or 200. UV can be captured in color settings, but the contrast is not nearly as great as it is in black-and-white photography. (If your camera does not have a setting for black-and-white photography, this same effect can be accomplished later using Adobe Photoshop or other imaging programs.) The lens aperture should be set to f5.6 or greater in order to allow as much light as possible to pass through the lens. Shutter speeds can vary greatly depending on the amount of light that is emitted from the ALS. A good start-ing point is one second and gradually increasing exposure times. In some of the tests conducted, exposure times were as long as 13 seconds. The camera should be mounted on a tripod and positioned at a 90 degree angle to the injury site. A shutter release cable or remote shutter release will need to be utilized.

According to Lee Frost in his 2002 book The Photographer’s Guide to Filters, the camera lens must be equipped with either a No. 15 Yellow or YA2 Orange filter. All test results showed conclusively that the YA2 Orange was superior in photographically documenting bruise type injuries. Position the camera and the light source about 10 to 12 inches from the target area to optimize the amount of light on the subject and the amount of light that is reflected into the camera. All injury sites identified during examination should now be photographed with and without a scale. (Note: Slow exposures are only applicable to those individuals who can be completely still for long periods—up to and beyond 13 seconds—during exposure. In order to photograph children, the film speed may need to be increased and the shutter speed changed accordingly.)

Getting started with
infrared photography

For infrared photography, a source of infrared light is a necessity. Many ALS systems come equipped with infrared attachments. However, another option is the use of a standard flash unit. The majority of flash units emit UV, visible, and infrared light. As in UV photography, filtering the camera lens is manda-tory to inhibit the passage of visible light through the lens. Good results with both a Wratten 18A and a Wratten 87 lens filter have been obtained. The camera must be mounted on a tripod and positioned at a 90-degree angle to the injury site. In most instances, the lens will need to be focused (these filters are opaque), and then the filter is affixed to the camera lens. Aperture setting should be f11 or smaller. Remember, IR penetrates the skin up to 3 mm, thereby necessitating a greater depth of field. The shutter speed is the flash unit sync speed which is normally 1/60th of a second. IR photography should also be performed in black-and-white with an ISO of 100 to 200. Depending upon exposure results, the ISO may need to be changed.

Infrared photographs will tend to appear out of focus. This is due to the fact that the camera lens is actually focused on the target surface and the resulting image is actually of something up to 3 mm further away. This can be corrected by focusing on the target, and then adjusting the lens to focus “deeper” into the target area. This will give an out-of-focus appearance when looking through the viewfinder, but the resulting photograph should be clearer.

An alternative infrared:
filtering the light source

An alternative action to filtering the camera lens is to filter the light source, which is, in most instances, a flash unit. Rather than purchase an expensive flash filter, a do-it-yourself filter can be easily fashioned from exposed and developed film. Most one-hour photo stores will develop exposed film free of charge. (To evenly expose the film, simply pull it out of the film canister and expose it to light. There is no need to load the film into a camera.) After processing, the film strips are cut and layered. Two layers is usually sufficient. The layers of film are then taped to the flash unit. It is imperative that no white light escape from the flash during IR photography. Depending on the flash unit, electrical tape may need to be applied to seams in the unit to prohibit light leakage.

You will find that this technique works very well because the light source itself is filtered. Since a lens filter is not needed, the camera can be utilized free-hand, thus allowing more movement by the operator.

Experimentation with
ultraviolet photography

During annual defensive tactics training, four individuals were chosen as test subjects in order to evaluate the UV and IR techniques previously described in this article. These individuals were monitored over a three-week period, or until their injuries could no longer be detected. For the purposes of this article, the accompanying photographs will focus on only one of the individuals monitored during the test.

The subject is a 33-year-old white male. Photographs of the injury that are shown in Photos 1, 2, and 3 were taken 16 hours after the injury was sustained. Note coloration of the bruise in Photo 1; the contrast in UV Photo 2; and the very slight contrast in IR Photo 3.



Photos 1, 2, and 3 (in sequence, left to right)

Photos 4 and 5 were taken 88 hours later. Note the color of the bruise in Photo 4 and the contrast in UV Photo 5. IR photography no longer yielded contrast of the injury.



Photos 4 and 5 (in sequence, left to right)

Photos 6 and 7 were captured 280 hours after the injury was sustained. The bruise had nearly completely faded as can be seen in Photo 6. But UV Photo 7 still yielded contrast.



Photos 6 and 7 (in sequence, left to right)

 

Experimentation with
infrared photography

Infrared was found to be an unsuitable technique in photographically documenting contusion- or bruise-type injuries due to the depth of the tissue that IR penetrates. However, IR proved to be quite useful use in capturing more severe injuries.

When photographing injuries it was noted that surface blood “disappeared” and a clearer image of the injury was obtained. Photos 8, 9, 10, and 11 were taken during an autopsy. Photo 8 shows an incised wound on the left side of the victim’s head. Photo 9 is an IR photograph of the same injury. Another benefit of IR photography is that tattoos can be discerned much easier. This can be seen when comparing the images in Photos 10 and 11. According to Dorion, IR can also be utilized in the case of a victim in advanced stages of decomposition in order to capture tattoos for identification purposes.



Photos 8 and 9 (in sequence, left to right)



Photos 10 and 11 (in sequence, left to right)

Conclusions

When either of the two techniques mentioned in this article are followed as described, the photographer can expect to obtain good to excellent results. These particular techniques are applicable to photography of virtually any type of injury, and as the photographic documentation clearly reveals, the injury is better depicted using these techniques. Although the IR technique is not as useful in bruise or contusion documentation, it is a useful tool in more serious injuries. It is imperative that all equipment be tested and that the operator devote time to extensive practice. These are only tools and a tool is only effective in the hands of a person who is well versed in the use of that tool. Further experimentation will need to be performed as technological advances are made.


TESTING THE EQUIPMENT

The following tests are effective ways to evaluate photographic equipment for UV and IR photography. Whether you perform these tests or not, contacting the manufacturer is highly recommended.

To test a camera and lens for ultraviolet sensitivity

Photograph a person with freckles or “liver spots” with standard lighting. An additional photograph is taken using the photographic technique previously described: ALS set to 450nm; camera set to black-and-white; aperture set to f5.6; shutter speed set to 1 second or longer; and a YA2 orange lens filter. If the freckles or liver spots are more pronounced in the latter photograph, then at least some UV is passing through the camera and the CCD is capturing it.

To test a camera and lens for infrared sensitivity

Photograph a person with dark pigmentation in their skin utilizing a source of infrared and follow one of the infrared techniques described in this article (using a filtered lens or filtered light source). If the resulting photograph depicts the person’s skin to be of a significantly lighter tone, then the camera is recording infrared.


About the Authors

Curtis D. Klingle serves as a crime-scene investigator with the Bryan (Texas) Police Department. He draws on more than 19 years of experience working in crime-scene investigation. Klingle can be reached at: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

Detective Kathryn Reiter serves in the Criminal Investigations Division at the College Station (Texas) Police Depart-ment. She received her BS in Sociology at Texas A&M University in 2000 and is currently working on completing a BS degree in Entomology-Forensic Science at the same university. She can be reached at: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it


ORIGINALLY PUBLISHED:
"Ultraviolet and Infrared Injury Photography", written by Curtis Klingle and Katie Reiter
September-October 2008 (Volume 6, Number 5)
Evidence Technology Magazine
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