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Evaluating High Dynamic Range (HDR) Processing with Regards to the Presence of Individualizing Characteristics in Shoeprint Impressions

NCJ Number
Date Published
17 pages
This study examined High Dynamic Range (HDR), a method for processing a series of photographs into one image that captures the fullest range of highlights and shadows present in the original impression.
Results found that HDR processing of multiple images does not produce a significant increase in detailed information compared with viewing the same images in Photoshop. However, exposure (auto) bracketing increases the ability to capture more detailed images of footwear impressions than a single image alone, and allows the use of HDR software for rapid processing and comparison. Difficult lighting situations that lead to challenging photographic conditions are common at crime scenes. The ease and accuracy with which the laboratory is able to analyze footwear evidence is largely determined by the quality of the evidence collected in the field. HDR is a method used to increase the span between shadows and highlights in an image by taking more than one picture of the same scene - shots that maximize shadows, maximize mid-tones, and maximize highlights - and then merging them into one unified picture with tremendous tonal range. It is imperative that the photographer accurately documents the scene details despite vast differences between the brightest areas and the darkest shadows. For this reason, if difficult lighting situations, limited equipment, time constraints, or resources pose a challenge at the crime scene, use the auto-bracketing feature. Auto-bracketing over a large exposure range is now available on many digital cameras. This will provide a quick, straightforward, and forgiving means of capturing the best image possible in the form of multiple source images. Tables, figures, and references

Date Published: January 1, 2012