An inverse densitometric circuit is described which employs the technique of voltage-transfer curve translation to provide a direct linear measure to photographic-energy profiles. An antilog D scale (reciprocal-transmittance scale) linear to ±0.05 antilog D units over a basic antilog D range of 12 is obtained. Neutral-density filters are used to compound the basic sensitivity increment and obtain a total light-level range in excess of 1 to 103. An optical system is described which provides an instrument resolving power of 500 lines/mm.
A. B. HOOK, L. F. GILLESPIE, and F. MASTRUP, "Energy-Recording Microdensitometer," J. Opt. Soc. Am. 51, 1402-1405 (1961)