The accuracy and reproducibility of measurement of the optical transfer function are dependent upon the differing sources of noise in various measurement approaches. These noise sources include: fluctuations in the light source, noise and drift in the detector, atmospheric turbulence and stratification, mechanical vibrations, and distortions in the structure of the bench. In addition, uniformity of illumination of the aperture of the system and uniformity of collection of the detector may affect the results.
D. R. Herriott,
J. H. Bruning,
"Modulation Transfer Function By Measurement Of The Pupil Function", Proc. SPIE 0046, Image Assessment and Specification, (1 June 1974); doi: 10.1117/12.953990; https://doi.org/10.1117/12.953990