The authors have made investigations with Super XX film and find that the resolving power in white light is strongly influenced by the shape and size of the blue and red images. The results indicate that if the imaging characteristics of a lens in white light are to be determined photoelectrically they should be done in at least three wavelength regions. As a by-product of the experiments it was found that the low-contrast resolving power correlated fairly well with subjective picture evaluation.
ROBERT E. HOPKINS, SUSANNA OXLEY, and JAMFES EYER, "The Problem of Evaluating a White Light Image," J. Opt. Soc. Am. 44, 692-692 (1954)