Gas discharges in point or parallel plate counters can produce a blackening effect on photographic emulsion layers inserted in such counters. The discharges are localized to points where ionizing radiation enters the counter. Arrangements of this type can be used for image intensifiers. A description of the operation of such counters and a proposed interpretation as to the physical mechanisms involved are presented.
K. S. LION and G. F. VANDERSCHMIDT, "Photographic Effect of Counter Discharges," J. Opt. Soc. Am. 45, 1024-1027 (1955)