INFRARED PHOTOGRAPHY

     Infrared photography is the recording of images formed by infrared radiation. 
Because infrared radiation is invisible, some special techniques may be needed.  But,
in general, most of the commonly required methods are as simple as those of ordinary
photography.

Uses In Law Enforcement

     1.   Questioned documents.
     2.   Aerial photography.
          a.   Infrared photography can enhance the contrast of the terrain.
          b.   Coniferous (darker) and deciduous (lighter) growth is
               differentiated.
     3.   Surveillance photography.
     4.   Detection of gunshot-powder burns, stains and irregularities in cloth.
     5.   Detection of certain types of secret writings.

Equipment

     1.   Camera
          a.   Almost any camera.  The 35mm camera is most convenient in
               most cases.
     2.   Lenses
          a.   Most good lenses can be used in infrared photography.  It is
               helpful if the lens has an infrared focusing scale.

Film

     1.   Black-and-White Infrared Film
          a.   Records infrared luminescence from subjects.
          b.   Requires an infrared filter on the camera lens.  Try a Kodak
               Wratten Filter #87.
     2.   Color Infrared Film
          a.   Not usually a good choice for law enforcement use.  Color infrared
               film is a "false color" film.  It is sensitive to blue radiation in all its
               film layers so a yellow filter must be used to filter out the blue.
          b.   Color infrared film can be used to emphasize differences between
               objects that are visually quite similar.  Color infrared-sensitive films
               emphasize differences in infrared reflectance.
     3.   Loading Film
          a.   Infrared film is sensitive to heat and should be refrigerated.  Allow
               sufficient time for the film to reach room temperature before
               opening the package.
          b.   Kodak High Speed Infrared Film must be loaded and unloaded in
               total darkness because the felt-lined slots of the magazines are not
               "light-tight" to infrared.  Both exposed and unexposed film can be
               safely stored in the sealed film container.

Lighting

     1.   Use tungsten lamps or electronic flash units for black-and-white infrared
          photography.
     2.   Use electronic flash illumination for color infrared photography.  Other
          light sources (except daylight) require special filtering.

Exposure

     1.   Exposure is determined by test shots.
     2.   Using Kodak High Speed Infrared Film with a Kodak Wratten Filter #87,
          try an ISO 25 for daylight and an ISO 64 for tungsten lighting.

Focusing

     1.   Focus in a normal manner without the filter in place.
     2.   The distance that appears opposite the normal index mark on the lens
          should then be moved to the red (infrared) index mark.  This will usually
          result in a lengthening of the lens.
     3.   Replace the filter for the exposure.

References

     1.   Kodak Applied Infrared Photography, 1981 (M-28)
     2.   Kodak Using Photography to Preserve Evidence, 1982 (M-2)
     3.   Kodak Photographic Surveillance Techniques for Law Enforcement
          Agencies, 1976 (M-8)