1. IR Photography Forensic Applications

2. Characteristics of IR Photography  In digital IR photography the sensor is sensitive to IR light –  Near-infrared is not far-infrared, which is for thermal imaging. Wavelengths range from 700- 900nm.  Filters used with infrared-sensitive sensors give interesting “in-camera effects“: false-color or black and white images with a dreamlike appearances known as the "Wood Effect,"  Caused by foliage (such as tree leaves and grass) strongly reflecting in the same way visible light is reflected from snow. There is a small contribution from chlorophyll fluorescence, but this is marginal and is not the real cause of the brightness seen in infrared photographs. The effect is named after the infrared photography pioneer Robert W. Wood.  Other attributes of infrared photographs: very dark skies and penetration of atmospheric haze, caused by reduced Rayleigh scattering and Mie scattering, respectively, compared to visible light.  The dark skies result in less infrared light in shadows and dark reflections of skies from water  Clouds stand out.  Near IR wavelengths also penetrate a few millimeters into skin and give a milky look to portraits. Eyes often look black. http://en.wikipedia.org/wiki/Infrared_photography

3. Visible (left) vs. Infrared (right @ 900nm) Aerial Photography Old Hickory Lake, TN Taken from a passenger airplane seconds apart using Sony H-9 Digital camera Water Absorbs Near IR Light Water Absorbs Near-IR Light

4. Digital IR Photography  Most digital imaging chips are sensitive to IR light  Must remove filter  How to check camera:  Turn off auto-focus & set camera to bulb using a wide aperture  In a dark room: open shutter, point TV remote control at lens & press button on remote  If end of remote glows, camera is sensitive to IR radiation Will be able to convert camera  Converting cameras  Remove IR filter Manufactures add filter to imaging chip that cuts IR sensitivity o Low pass filter o Removing requires complete teardown of camera, removal of imager  Using an IR lens Example #87 Wratten filter o Can put high-pass filter on imager behind shutter in place of Wratten filter Use a tripod  Example of exposure on sunny days  1/60@f/11, ISO 200

5. What do you Need to Know?  Where in the electromagnetic spectrum is the IR region  What part of the IR region is used  What are the sources of IR light  How to interpret filter data  What are the applications  Under what circumstances would you use IR photography

6. The Electromagnetic Spectrum Using Light to Find Evidence 190-290290-400 Ultraviolet Region Short wave Long wave Visible Region 400-455 455-492 >700 492-577577-597597-622622-700 Infrared Region Violet BlueGreenYellowOrangeRed IR Near IR – NIR ~ 700-1200nm Far IR – FIR > 1200nm

7. Maglite Infrared Light Sources  Digital IR photography typically relies on a NIR light source  Sun  Incandescent lamps  Digital camera sensors based on silicon: NOT sensitive to the far (thermal) IR (typically > 3.0µ )  To photograph in the dark  Provide proper NIR illumination  External NIR-only flash with no filter

8. Blocking Light Entering Camera Bandpass Filters  Block wavelengths of light from hitting the digital sensor  Allow unblocked wavelengths into the camera  Different Filters have different characteristics Camera Sensor Bandpass Filter Blocks Visible & UV Light Allows Near IR Light to Pass Through Near IR Light Light: Visible/UV/IR

15. Predominately a Red Color Photographed

17. X-Nite Filters

18. BPBBPGBPR IR Selective Filters

20. Forensic IR Applications

21. Gunshot Residue Black t-shirt T-shirt does not absorb Infrared light GSR Particles

22. Searching for Blood @ Crime Scene Dark Surfaces That Do Not Absorb in the Infrared

23. IR Photography of GSR Through Bloodstains GSR Particles Blood Absorbs In the IR

24. Check Fraud In 830nm (Deep BW) Infrared light you can clearly see the original amount was $100 In visible light the check looks to be written for $400 dollars http://www.lifepixel.com/galleries/forensic-photography-gallery

25. Post-Mortem Photography http://www.evidencemagazine.com/index.php?option=com_content&task=view&id=106&Itemid=49