Empirical data on visual detection and recognition of photographic detail as recorded on the photographic negative are presented in terms of sizes and contrasts in the object space. The performance of diffraction limited systems is given for five emulsions.
DUNCAN E. MACDONALD and JOHN T. WATSON, "Detection and Recognition of Photographic Detail. I. Empirical Data Applicable to the Prediction of Performance of Diffraction Limited Systems," J. Opt. Soc. Am. 46, 715-718 (1956)