The measurement of the modulation transfer function (MTF) is one of the key steps in characterizing the signal transfer characteristics of an imaging system as a function of spatial frequency in terms of linear response theory. Various methods have been proposed to determine the MTF of an imaging system which are based on point, slit or edge images. The slanted-edge method is the ISO 12233 standard for the MTF measurement of electronic still-picture cameras. In this paper, the method is modified to avoid amplifying the noise during the derivative computation by performing curve-fitting. In the experiments, we compare several different analytical function models for the ESF fitting and find that Logistic (Fermi) function gives the best result.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.