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NCJRS Abstract

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NCJ Number: 200466 Find in a Library
Title: Background Correction in Forensic Photography I. Photography of Blood Under Conditions of Non-Uniform Illumination or Variable Substrate Color--Theoretical Aspects and Proof of Concept
Journal: Journal of Forensic Sciences  Volume:48  Issue:3  Dated:May 2003  Pages:593-603
Author(s): John H. Wagner; Gordon M. Miskelly Ph.D.
Date Published: May 2003
Page Count: 11
Type: Report (Study/Research)
Format: Article
Language: English
Country: United States of America
Annotation: This paper discusses the application of a background correction technique to photographic images to provide increased discrimination, using bloodstain evidence as an example.
Abstract: In photographing crime scenes and forensic evidence, there are some circumstances in which either variable lighting of the surface of interest or patterning of the surface on which the evidence sits can produce a relatively poor view of the evidence in a given photograph. These problems can be reduced or eliminated by performing background corrections on photographic images. The authors first explain the theory of the background correction method in a quantitative manner for transmission mode photography; the theory is then extended to approximate treatments of "normal" (reflectance) photography. The treatment is based on the use of a consumer digital camera that can provide linear images and that has controllable variable shutter speeds. The camera used in the work described in this paper was a Canon D-30 digital single lens reflex, with either a Canon 24-85 mm zoom lens or a Canon EF 100 mm F2.8 mm macro USM lens attached. The case examples described in this paper involved the enhancement of photographic images of bloodstains on problematic materials, i.e., a dark red rumpled shirt with a glossy finish, dark blue stretch jeans, and black jeans with blood and dirt. The production of background corrections through three wavelength linear images provided the best detectability of blood in the photographic images. The entire process is based on the mathematical treatment of the whole image consistent with standard analyses of absorbance or reflectance. 9 figures and 21 references
Main Term(s): Police policies and procedures
Index Term(s): Blood stains; Camera technology; Evidence collection; Forensic sciences; Photography; Photography techniques; Police photography training
Note: For part II of this paper, see NCJ-200467.
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