A new wide-range logarithmic circuit for a light-intensity meter is described. The circuit, consisting only of photoconductors and constant resistor, takes advantage of the inverse power law that the photo conductors obey. The indicator (miocroammeter) used is of simple linear type: the deflection is proportional to the current. Accordingly, the over-all response is logarithmic in light intensity. An experimental unit covering more than four decades of intensity is described. The same principle may be applied to nuclear radiation meters.
DAVID S. GREY, PETER MARK, and STANLEY HASKELL, "New Class of Wide-Range Logarithmic Circuit for a Light-Intensity Meter," J. Opt. Soc. Am. 50, 40-43 (1960)