Photographing a footwear impression in dust is sometimes
difficult, especially if the dustprint is on a highly reflective surface,
such as a gelatin lift or mylar from an electrostatic dustprint lift. Either
reflective surface will cause glare back into the camera from the light
source. However by using the ALS, a beam of light can be positioned so
the light is parallel and just above the reflective surface. This lighting
technique has proven successful in photographing these difficult surfaces.
No camera reflections, no light flares, no hot spots - just even lighting
for a photograph suitable for comparison to the suspected footwear.
This lighting technique can be used on any surface, not
just highly reflective surfaces. Footwear patterns found on concrete, wood
floors, tiled floors or any surface that oblique lighting identifies an
impression. The use of the ALS should not be confined to just oblique lighting
for footwear but also for lighting any dust impression, such as a finger
or palm print, fabric impressions or to photograph the dust to show the
disturbance or lack of disturbance at the crime scene.
Exposure time has been approximately 12 seconds at F4
with 100 ISO film. Exposure will depend on the intensity of the light source
and the distance between the light source and the object to be photographed.
The light source must be held almost parallel or you will
have uneven illumination of the object you are attempting to photograph.
The white light frequency on the ALS should not be used for more then 45
seconds with the fiber optic cord attached. The power output may burn the
fiber optic cord. However if you are using a liquid fiber optic cord no
harm will be done. The other light frequencies will not effect the fiber