The hours during which useful photo-reconnaissance can be carried out are limited by the speed of the film on which the images are recorded. The capability of recovering information from photographic negatives which have been severely underexposed would significantly extend that limitation. This paper describes a system for imaging information contained in an ultra thin (i.e., severely underexposed) negative by means of light that is scattered by the individual particles comprising that information. Density vs. exposure curves displaying the behavior of the system are presented. Examples are given showing that the use of this scattered light system together with common metal toning enabled the recovery of information from photographic film underexposed as much as six "f" stops.
K. Murray, K. Murray,
"A Scattered Light Imaging System", Proc. SPIE 0242, Long Focal Length, High Altitude Standoff Reconnaissance, (23 December 1980); doi: 10.1117/12.959274; https://doi.org/10.1117/12.959274