In cases in which there are zeros in the optical transfer function, display of the absolute value of the Fourier transform of a blurred image may allow these zeros to be seen, if the noise level is low enough. This can be used to identify the optical transfer function, provided that it is one of the suitable common simple forms, or to determine certain parameters of the optical transfer function if its form is known. Examples of the use of this technique in the generation of restoring filters for image enhancement are presented.
Donald B. Gennery, "Determination of optical transfer function by inspection of frequency-domain plot," J. Opt. Soc. Am. 63, 1571-1577 (1973)