NCJ Number
113370
Journal
Journal of Forensic Identification Volume: 38 Issue: 3 Dated: (May-June 1988) Pages: 83-90
Date Published
1988
Length
8 pages
Annotation
This study examines the effect of the electronic flash for photographing three dimensional impressions in various soil consistencies during daylight conditions, with attention to film speed, flash angle, and distance to the impression.
Abstract
All of the test photographs were taken during midday hours with the weather clear and mostly sunny. A flash-to-subject distance of .85 meters was used. This distance allows one person to hold the flash, operate the camera, and if necessary, cast a shadow over the impression. The flash was held at a 45-degree angle to the subject, since an angle of less than 45 degrees can result in uneven lighting across the impression. The aperture adjustments on the camera were needed for reducing the ambient light being reflected from the subject to the film, thereby allowing the flash to be the dominant light source. The exposures were made while casting a shadow over the impression to eliminate as much of the existing ambient light as possible. The amount of subject light reflectance was determined by using the camera's light meter. Negatives were developed at a variety of contrast indexes (C.I.). Based on an evaluation of these results, a C.I. between 0.70 and 1.0 appears optimum. 3 figures, 1 table, 5 references.