Ultraviolet & Infrared Photography
Written by King C. Brown & M. Dawn Watkins   

Photography is the driving force behind any crime scene investigation. It is the best means of recording the scene of a crime. Photography produces courtroom displays that bring the jury to the crime scene. Everyone looks at and understands what a photograph is and what it represents. Looking at a photograph and seeing the evidence that is usually invisible is a new concept. Finally, with little preparation, a few filters, and remarkable upgrades in equipment, we can see the invisible—the hidden evidence.



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UV/IR Specifics
 
The human eye—and the camera (with the standard filter attached to the sensor)—see in the visible light spectrum, from approximately 380 to 700nm. By simply removing the interior filter and replacing it with clear glass, camera manufacturers have created UV/IR cameras that “see” in the spectrum of approximately 350nm to 1000nm, thus visualizing “invisible” evidence.
 
How does this assist the investigator? Evidence that could not be photographed before now can be easily captured. Blood on dark clothing, gunshot residue, semen, hair, questioned documents, ink differences, partially burned items, and much more can be captured be made visible with a UV/IR camera. With a little bit of practice and a good tripod, you can capture ultraviolet and infrared images with excellent results.
 
The special black-and-white mode in most cameras allows for capture of forensic images in UV or IR using filters from Peca Products, Inc. and an alternate light source. The light source doesn’t need to be an expensive ALS, just a source that emits UV and IR light—for example, a 100-watt light bulb will suffice.
 
How the UV/IR Camera Works:
 
The latest UV/IR camera to be developed and marketed to the crime scene investigation and health care communities, the Fujifilm X-T1 IR, functions just like any single lens reflex or mirrorless camera. This mirrorless camera handles well and has a very firm grip with a vertical shooting exposure button that assists in vertical photographs. In experiments in both regular color photography and black-and-white photography, the camera responds very well to low-light conditions with a variable ISO range from below 200 ISO to over 6400 ISO. This proves very functional for low-light and forensic photography.
 
One of the assets of the UV/IR camera is the live-view preview mode. This is particularly useful when using special UV/IR filters, since they are totally black and don’t emit light in the visible spectrum. The live-view preview mode allows one to focus the camera when the filters are attached. This eliminates issues with out-of-focus photographs and moving the camera lens when installing the filters. The live-view preview mode is very easy to operate. This feature assists the photographer and allows for focused photographs with no fuss.
 
Filters
 
The UV/IR camera system requires the use of several filters for the capture of ultraviolet and infrared images. The filter system, manufactured by Peca Products, is divided into two sets of filters: the basic filter pack and the complete filter pack.
 
The basic filter pack includes:
  • Digital Filter PECA 900 (#18A)
  • Digital Filter PECA 904 (#87)
  • Digital Filter PECA 910 (#87C)
  • Digital Filter PECA 914 (#89B)
  • Digital Filter PECA 916 (IR & UV blocking/visible pass filter)
 
The complete filter pack includes all of the above and:
  • Digital Filter PECA 902 (#70)
  • Digital Filter PECA 906 (#87A)
  • Digital Filter PECA 908 (#87B)
  • Digital Filter PECA 912 (#88A)
  • Cost of the filters is a bit of a shock at approximately $115 each.


A filter kit from Peca Products is required to use the Fujifilm X-TI IR camera for documenting evidence with ultraviolet and infrared light.

 
Instructions for Ultra-Violet Use & UV Theory
 
Bruises, Bite Marks, and Needle Marks
 
Reflective ultraviolet photography for bruises, bite marks, scar tissue, and needle marks records the reflection and absorption of long-wave UV light by the subject matter, excluding exposure of the sensor to all visible light. Simply said, long-wave UV light penetrates deeper into the skin than does visible light. Therefore, by placing a specially designed filter over the camera lens—one that will only allow a specific wavelength of UV light (less than 400 nm)—we can expose the sensor to only this light. Since UV light penetrates deeper into the skin, the sensor will pick up the image of a bruise or bite mark, which has been absorbed too deep into the skin to be seen using visible light. The time frame to obtain good results with this technique has never been fully explored. Photos taken using this technique will not show bruises that are still visible. The earliest time in which these photos seem to show any image is shortly after the bruise or bite mark is no longer visible to the unaided eye. The longest documented period is at least five months after the injury. In one documented case, an infant's injuries (bruising) were almost 3 months old when UV images visualized fingermarks on the infant's chest, where the child had been shaken.
 
The technique for imaging bruises and bite marks:
 
1) The camera is set at ISO 400, shutter speed 1/60, and flash synchronization is set for electronic flash.
 
2) Mount the camera on a tripod. The best UV photos are taken parallel with the subject. You must adjust the tripod so that as little of an angle as possible exists between the subject and lens.
 
3) Position the victim comfortably about 12 to 14 inches from the lens. Again, ensure that the lens plane and bite mark or bruise plane are parallel.
 
4) Take a visible light (unfiltered) photo of the area, and general orientation photos.
 
5) Focus the camera, instruct the victim that you will be taking a series of about three to four photos, and they must keep their movement to a minimum during the process. Place a scale or other measurement device on the injured area, being sure not to block the injury itself.
 
6) Re-check the camera focus. Then place the UV filter on the camera (begin with the Peca filter #914, then #910, and then use a B+W UV/IR cut 486M MRC filter), and take several exposures with each, setting the aperture to f/5.6, f/8, and f/11.
 
7) In order to achieve optimum results, you can then hold your flash or light source in a different position relative to the injury and re-shoot, using the same bracketing.
 
8) Lots of light is the key to good photos. Make sure the flash is pointed in the direction of the injury.
 
Fingerprints with Fluorescent Powders
 
UV/IR photography does a fantastic job capturing UV photographs of fingerprint evidence with the Peca visible pass filter #916 and UV light. The camera can be set on ISO 400, Aperture Priority mode, and f/16, mounted on a tripod or copy stand, resulting in very fine-quality images. No other filtration is needed with florescent powders and the UV/IR camera. Images can be captured in either black-and-white or color and should be photographed in RAW image format, thus resulting in a very high-quality image.
 
Semen, Urine, and Other Body Fluids
 
The capture of biological stains is extremely critical in solidifying a case of sexual assault. Set the UV/IR camera on ISO 400, Aperture Priority mode, and f/16; attach the Peca #916 visible pass filter; and add UV light. Be sure to place the camera on a tripod or a copy stand and use a scale.
 
Questioned Documents
 
When photographing questioned documents and there is a possibility of a different type of ink or pen being used, the infrared capabilities of a UV/IR camera are brought to the forefront. The camera is mounted on a copy stand with the document properly framed and with an exposure of 1/4 sec. and f/22 for maximum depth of field. Adjust the exposure for the type of lighting used, and then the documents can be photographed quite easily and, when adding the proper filtration, excellent results are obtained. We photographed a check with all of the filters of the Basic Filter Pack, and the results obtained determined that the check was altered.
 
Possible Blood Stains
 
The combination of the Fuji XT-1 IR Camera and the infrared filters is an asset for the photography of possible bloodstains on dark-colored clothing. By using the copy-stand method and proper lighting, you can produce excellent quality photographs of most any possible blood stain. Start by setting your camera to ISO 400, 2 seconds, and f/8, and then adjust your shutter speed for lighting. Take several exposures of the item of evidence; be sure to include the Peca #916 visible pass filter for an establishing photograph of the item of evidence. Also photograph the individual under investigation in color with the Peca #916 visible pass filter to document the appearance of possible blood stains.
Blood stains on dark fabric were first photographed without a filter (top) and then with an infrared camera and Digital Filter PECA 914 (written filter #89B) (bottom).
 
 
Gunshot Residue
 
Gunshot residue is one of the easiest items of evidence to photograph and takes very little time and effort. Place the item of evidence on a flat surface with good lighting such as a photo-flood lamp or some other emitter of infrared energy. Place your camera on a Quadra-Pod, tripod, or copy stand. Take a series of photographs using all of the available filters, with the camera set to black-and-white mode, ISO 400, 2 seconds, f/22 to start, and adjust the shutter speed for the particular lighting used. Try to maintain the f/22 setting for maximum depth of field and to help capture the impression-depth of the writing. Be sure to include the Peca #916 visible pass filter for an establishing photograph of the item of evidence. You may also want to photograph the item of evidence in color with the Peca #916 visible pass filter. (Note: Lead-free ammunition with smokeless powder will not show GSR under IR light.)
 
Surveillance Photography
 
Since infrared light is not visible to the human eye, an IR light source cannot be seen by your subject. Using various IR light sources, which can be focused to a distance, will allow IR photography of suspects for surveillance. The photographs will be most useful in black and white. The advantage of this method is the use of totally invisible light sources.
 
Available Equipment
 
There are several companies that sell UV & IR Photographic equipment. This is a partial list of available UV/IR Equipment:
 
  • Fuji Film XT-1 IR Digital Mirrorless Camera with lots of features, designed for the crime scene investigator;
  • Arrowhead Scientific carries the CrimeCam Full Spectrum Imaging System, designed for laboratory use, with a separate model for scene work.
  • Conversion systems are also available for converting a current digital camera to use with UV & IR photography. Note that on this type of application, you are usually using older technology.
 
Conclusion
 
The new advances in UV/IR digital photography are surely an asset to the crime scene investigator and to the forensic science laboratory. For the photographer who knows nothing about ultraviolet and infrared photography, a little research and practice can pay off big with excellent photographs.
 
About the Authors
 
M. Dawn Watkins is a senior latent-print examiner and crime-scene investigator at the Palm Beach Gardens (Florida) Police Department. She has been in the forensic field for 42 years, holds a master’s degree in criminal justice, and is an IAI Certified Latent Print Examiner, Certified Senior Crime-Scene Analyst, and a Certified Forensic Photographer.
 
King C. Brown is the crime scene supervisor with the West Palm Beach (Florida) Police Department. Brown has been in the field of forensics for 32 years, holds a master’s degree in criminal justice and is an IAI Certified Latent Print Examiner, Certified Senior Crime-Scene Analyst, and a Certified Forensic Photographer.
 

 

 
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