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RECREATING THE NIGHTTIME SCENE

Photographs, especially of nighttime scenes, can be very frustrating: it is possible with a photograph to make night look like day. Conflicts frequently arise in court between experts as to which photograph most accurately depicts a scene. How do you know, for example, which of Photographs A or B best represent the nighttime scene?

Our experience in litigation and in providing support to the insurance industry has proven to us that the ability to illustrate the circumstances observed at a nighttime accident scene is crucial to an effective presentation of our reconstruction opinion. Ultimately, this allows the judge or jury to "stand in our shoes" at the scene, providing them with a better foundation on which to base the important decisions they must make. Walters Consulting Corporation has over the years developed a simple to understand, "court-friendly" solution to the problem of reconstructive nighttime photography.

Producing a photograph of low illumination scene that reasonably represents the observer's view is not simply a matter of taking a 35mm camera to a scene and snapping a few photographs at various shutter speeds. Under poor illumination conditions, the human observer loses his capacity to discern colour and sees in "black and white". The goal is to produce a black and white print having tones of gray approximately representative of those perceived by the observer. An additional concern is that a normally made black and white print will over represent red objects (objects that would appear red under higher illumination); this is because the film is sensitive to low level red light while the human eye is not. As well, one can produce a print that shows far greater detail, or far less, than was observed at the scene, simply by adjusting exposure or printing procedures.

Our procedure is to select a film that approximates the sensitivity of the human eye, and to filter the incoming light to absorb a proportion of incoming red light and to attenuate the film's sensitivity to ultra violet radiation, which the human eye cannot see. As well, we add a reference object to the scene so that we can adjust the printing process to produce a print that reasonably replicates observations made of the site. This is best explained by reference to Photographs A and B, both of which were printed from the same negative.

The checkered target board to the left of the scene (most clearly visible in Photograph A), is a basic prototype version of the target board we used to record the contrast that we are able to discern at a scene; it is painted with rectangles of various shades of gray, each adjacent to black squares of the target board and was just able to see the lower left square. Print A shows that the negative was more "sensitive" than the human eye (due to the long exposure); it was able to record the presence of each contrasting shade of the board.

Photograph B illustrates reasonably well the visibility of the scene as observed. The upper corners of the contrast board are not discernible while the lower left corner marginally is. Photograph B is the print that we would use to illustrate our observations and to support conclusions as to the visibility of the pedestrian in the scene; the relatively low contrast of the pedestrian shown in Photograph B is readily apparent.

 
The information contained in this web site is intended for marketing purposes only. It is not all-inclusive, and does not fully describe the many and varied services that the company provides, nor does it completely describe the education, training, skills, or expertise of our staff.

 
 
 

Walters Forensic Engineering | 277 Wellington Street West, Suite 800 | Toronto, ON M5V 3H2
Information contact: engineering@waltersforensic.com