Photographic Resolution

Photographic recording of an accident or crime scene, or other venues where a forensic investigation is held, is vitally important. After the scene has been cleaned, photographs preserve the scene in time and allow visual analyses to be done long after the fact. The quality of the photographs is therefore extremely important. This is the reason why forensic photography is the domain of a professional photographer, rather than, for example, the investigating officers.

A critical aspect of photographic quality is resolution. The term resolution in the context of photography refers to the degree to which adjacent objects can be distinguished from one another in a photographic image. Obviously, the higher the degree of resolution—which is a function of the acuity of the photographic equipment used, as well as the abilities of the operator—the better the quality of the photograph.

The lower the figure given for the resolution, in metric or English units, the higher the degree of resolution. For example, the first four satellites of the CORONA project, which remained aloft throughout most of the period from June 1959 to December 1963, had a relatively high resolution of 25 feet (7.6 m), meaning that objects smaller than that size were likely to be indistinguishable from one another. Higher still was the resolution of the fifth satellite in the series, KH-4B (September 1967 to May 1972), at 6 feet (1.8 m). Photographs taken by KH-5, a satellite deployed for mapping purposes between February 1961 and August 1964, had a much lower degree of photographic resolution: 460 feet (140 m).

Modern satellite cameras such as Landsat, SPOT, and Quickbird digital imaging systems send photographic images that show resolutions of 2 feet (0.62 m) for panchromatic images and 7.9 feet (2.4 m) for color images. Quickbird images were used to help identify debris from the space shuttle Columbia, when it exploded over Texas in 2003.