“[…] Improperly Photographed Impressions:

If the examination involves a photographed tire impression, many things can affect the dimensional accuracy of that photograph. If the camera’s film plane (back) is not perfectly parallel to the impression, then the photograph will have a perspective problem that can affect the ability to accurately enlarge the photograph of the impression to its natural size. This type of problem usually occurs due to errors in photographic procedure. Another problem commonly encountered occurs when the scale (ruler) is not placed on the same exact plane (level) as the bottom of a three-dimensional tire impression or when the ruler is resting on the ground at an angle. If the ruler is not on the same plane and parallel with the bottom of the impression, an accurate enlargement will not be possible. Photographic procedural errors often result in limited examination results. Casts can resolve these problems, but unfortunately some impressions are only photographically recorded and thus the examination must rely on those photographs alone […]”

William Bozkiak, Tire Tread and Tire Tread Evidence