A resolving power criterion is used to evaluate a method which utilizes the Herschel effect to improve the resolution of aerial photographs. The maximum resolving power is increased and the useful exposure range is considerably widened in a Herschel print. To minimize exposure times, the sensitivity of Kodabromide paper to the Herschel effect is increased by a desensitizer. Although equivalent resolution may be obtained by the use of unsharp masks, the economy of time and material in the Herschel method makes it superior for application to mass printing operations.
MARY JOHNSON, "Use of the Herschel Effect in Improving Aerial Photographs," J. Opt. Soc. Am. 41, 748-749 (1951)