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By: Jason Schneider  
Issue: Dec. 2006/Jan. 2007

Digital technology is putting crime labs on the fast track by making infrared and ultraviolet photography easier, quicker, and less expensive then ever before.

The forensic use of infrared and ultraviolet (UVIR) photography to evaluate forged documents and counterfeit currency, gunpowder residues and tissue abrasions, and virtually every other imaginable type of physical evidence is a technique that goes back many decades. It has been used experimentally since the late 19th century and as a routine procedure in cutting-edge crime labs since the first commercial infrared films became available in the early part of the 20th century. However, until quite recently, shooting UVIR was a time-consuming, laborious, and rather expensive process that entailed the use of films with special handing requirements and demanding processing procedures.

To quote Chuck McKern, an experienced IR expert, “It’s difficult getting the film, difficult shooting with it, and difficult processing it.” Infrared film must be handled and processed in total darkness, is susceptible to static markings in low humidity, and requires a series of tests using heavy filtration (such as a No. 87, 87C, or 89B filter that blocks all UV radiation and visible light) to determine the best exposure. Focusing is often problematic and must be adjusted by noting the correct visual focusing distance, then resetting it opposite the IR index on the lens to correct for the focusing discrepancy between visible light and IR. Exposures are generally quite long, another major inconvenience.

UV photography using conventional blue-sensitive silver-halide film, light or medium yellow filters, and UV emitters for illumination, is somewhat easier, but optimizing a UV setup still requires a considerable amount of trial and error. In short, while film-based IR and UV photography can and does provide very good results in forensic applications and can record a wide dynamic range, neither can provide instant feedback on exposure, filtration, and other key variables. That single crucial factor severely limits the operational efficiency of film-based IR and UV imaging, and that puts a crimp on both the speed and productivity forensic investigators can achieve. It’s the old “time is money” factor rearing its ugly head, and what’s even more important, having to wait days or weeks to get crucial information makes it that much harder to nail the bad guys!

Black T-Shirt with Blood Stain,
captured with the FinePix S3
Pro UVIR using a 700nm filter
Photo courtesy of Julio Sosa, Biomed
Studio.

MOVING TOWARD A DIGITAL SOLUTION
Ever since the dawn of the digital era around the year 2000, innovative scientists and technicians in the forensic, medical, and academic communities began looking for creative ways to adapt this new technology to their particular research areas. Inevitably, a number of talented forensic researchers turned their attention to the knotty problem of digital UVIR imaging. In the beginning they were not aiming so much at enhanced speed, convenience, and quality but simply a workable method for doing it at all. Some forward-thinking specialists could foresee the day when niche-market films like IR would be severely curtailed or even go away, and they wanted to be sure they had viable alternatives.

They soon discovered that the digital revolution posed its own unique set of problems in creating a workable UVIR imaging solution. Since the CCD and CMOS image sensors in virtually every digital camera incorporates strong UV and IR filtration in order to achieve good color accuracy with ordinary visible-light subjects, digital cameras are not very sensitive in the UV and IR spectrums and are therefore inconvenient to use in these applications. When experimenters tried shooting IR or UV images with an ordinary, unmodified digital SLR (by far the most flexible type of camera for forensic use) they discovered that very long exposures were required and that manual focusing wasn’t always easy.

HUT Split Screen. The left side of the split is a "non modified" S3 Pro, while the
one on the right is an S3 Pro UVIR with ALS UV light assistance and no filtration.
Photo courtesy of Fujifilm USA

While the CCD and CMOS sensors in D-SLRs have an inherently high sensitivity to both IR and UV, the combined IR and moiré-reducing filter in front of the actual sensor is all too effective in dramatically reducing it. Indeed, the only reason these early experimenters were able to get any IR or UV images at all is because these filters aren’t perfect – they allow a tiny amount of IR and UV to pass through. Rather than muddling along by operating at the margins of these slight imperfections, the forensic technicians and assorted specialists took the “bull by the horns” and began modifying their D-SLRs by removing the UVIR filters. Over the last five years, this has grown into a veritable cottage industry, with a handful of small independent companies offering D-SLR conversion services. Unfortunately removing the filter is an expensive procedure that leaves the sensor unprotected. And even if it’s properly done, it voids the camera’s warranty, not a trivial consideration when it comes to cameras selling for $1,500-$5,000 each. In fact, many forensic agencies flatly prohibit modification of their cameras.

Photo taken with the FinePix S3 Pro UVIR using a long range IR assisted light
surveillance with no filtration. Photo courtesy of Julio Sosa, Biomed Studio.

THE SOLUTION: AN ADVANCED UV AND IR D-SLR
The roster of popular D-SLRs custom modified for forensic and scientific use include several models made by Nikon, Canon, and Fujifilm. One example is the Fujifilm FinePix Pro S3, which also uses the Nikon mount popular with law enforcement agencies. One reason that forensic specialists, in particular, favored this model for UVIR modification is that it employs a unique double photodiode (6.17 million S-pixels and 6.17 R-pixels) Super CCD SR II image sensor that provides a greater dynamic range than single-pixel sensors, along with very low noise. Both these characteristics are crucial for those who need to capture fine detail in both the shadows and highlights in order to uncover evidence not visible to the human eye.

This camera also has a Live Preview feature that works in conjunction with the mirror lockup. When you lock the mirror up what you see on the LCD is a live feed of the image formed by the lens that’s taken directly off the CCD. So, when the camera is UVIR modified, the LCD displays what the camera sees in the otherwise invisible IR and UV spectrums. This allows manual focusing under IR and UV illumination even when dark IR filters are mounted on the lens, as well as providing pre-capture image verification of the effect of filter changes. Both these capabilities streamline and speed up the process of IR and UV photography to a remarkable degree; what used to take days now takes minutes of even seconds. While independently modified DSLR cameras were certainly a great step forward for forensic applications, there was still not a factory-made, fully warranted product in this category with all the kinks removed and the tweaks applied.

Writing obliterated by paint.
Sample #1. Image captured with a Nikon D2h using a 60mm Nikkor
Lens, Mp-4 Copy Stand, 45 Cross-lighting Photofloods.
Sample #2. Orange LCD Close up. Captured with the S3 Pro UIVR
using a 60mm Nikkor Lens MP-4 Copy Stand, Kaiser 250w Light
Tungsten single light source. Kodak Wratten 87C filter.
Photos courtesy of Brooks Photographic Imaging, LLC

FORENSIC EXPERTS + CAMERA EXPERTS: SYNERGY CREATES NEW TECHNOLOGY
In mid 2005, a group of the forensic imaging users from a variety of local and national law enforcement agencies got together with the technical experts of Fuji-film USA and began to formulate a plan for designing an official production version of a digital SLR for UVIR photography. As a result of this dialogue, designers and engineers from Fujifilm USA worked closely with this informal group of end-users in a collaborative effort to devise a camera that would do all the things necessary to make UVIR in forensic work more reliable, convenient, and affordable. Shortly thereafter, an Alpha version of the new camera was made available for field testing and analysis by researchers at the FBI National Training Academy, the Coroner’s Division of San Bernadino County Sheriff’s Department, and several other more covert government agencies. Though impressed with the camera’s overall performance, these hands-on forensic specialists suggested a number of operational and design modifications, and the designers were able to incorporate many of their ideas.

After about six months of this creative and productive back-and-forth collaborative development effort, Fujifilm in Japan entered the picture, a clear indication that the manufacturer was committed to developing the prototype into an off-the-shelf product – the world’s first factory-made and supported UVIR digital SLR aimed at the forensic/medical/scientific market. The resulting Beta model had improved CCD algorithms and performance parameters, and a special clear glass filter designed to protect the sensor from dust and debris and facilitate cleaning. It also featured new software designed to make the camera more user friendly in a UVIR environment; for example by bringing the Live Preview mode to the top screen in the menu selections.

It was clear from the enthusiastic response and positive feedback by the forensic community that the Beta model was very close to being the finished product. After a remarkably short development cycle of just over a year — an amazing feat —the new camera into limited production as the Fujifilm FinePix S3 Pro UVIR, which will be bundled with HyperUtility Processing Software, providing investigators with convenient side-by-side image comparisons along with metadata analysis, both very useful tools when examining images of blood stains, documents, and other forms of evidence.

Other features of the new camera include RAW capture which, with HyperUtility software, provides a secure way to capture, manage, analyze, and output the 16-bit TIFFs often required by the law enforcement and forensics community, compatibility with most AF Nikkor lenses, five-area AF (which may not perform well in IR and UV applications), shutter speeds from 30-1/4000 sec with X-sync up to 1/180 sec., a 2-inch LCD monitor, and single frame and continuous shooting to 2.5 fps.

REAL WORLD ADVANTAGES FOR FORENSIC PROFESSIONALS
How well does the new camera actually work in day-to-day forensic applications? Julio Sosa, President of Biomed Studio in Miami, Florida observes, “The ability to capture and examine IR and UV images at the moment and to get the information I need is of immense value. I can set up a picture with the S3 Pro UVIR and look at the results in 30 seconds, and Live Preview lets me judge and correct everything in real time —including focus, filtration, lighting, and detail. This camera will also be a boon for Homeland Security people in twilight surveillance, and no Alternative Light Source (ALS) is needed in most applications. The camera’s wide dynamic range is also very significant because you can capture a crime scene without using Photoshop or other image-enhancement programs. That’s vital in courtroom presentations because you can answer truthfully that you didn’t alter the image one iota. The ability to capture extra black; that is, shadow detail; is also a real plus when outputting the image to a screen or hard copy.”

Images captured
with the S3 Pro
UVIR. Top image
used no filtration,
middle image used
a 720nm filter and
the bottom image
used a 850nm fil-
ter. Photo courtesy of
Julio Sosa, Biomed
Studio.

Other areas where the new camera surpasses previously existing technology in terms of performance, speed, and efficiency include:

• Latent fingerprint identification, especially where a confusing background such as print on a soda bottle must be dropped out to see the print clearly.w The ability to examine “invisible” blood stains on black clothing and weapons at a crime scene to provide immediate probable cause for detaining suspects.
• Picking up subtle gunshot residues and burn patterns.
• Capturing and displaying the alterations in a forged document, or the information hidden in an obliterated document using very short IR exposures and with instant visual feedback.
• Choosing the correct filters in real time for enhancing the identification of physical evidence including skin abrasions, chemical residues, and fibers.
• The ability to observe and identify details in dark or low-contrast subjects as a result of its wider exposure latitude.

At the end of the day, this camera is an important step forward, not primarily because it incorporates startling new technology but because of its unique design philosophy: If you want camera specifically designed to meet the needs of forensic specialists, don’t just listen to what they want, make them part of the design team. Creative collaboration is what made it all possible.

Jason Schneider has been writing about cameras and imaging technology for more than 30 years. He was Editor-in-Chief of Popular Photography for over 15 years, is currently Senior Editor of Photo Industry Reporter, a trade magazine, and freelances for a variety of consumer magazines and websites. Jason can be reached at popeditor@hotmail.com