Image contrast and edge slope are frequently used to assess image quality. But in the case of two‐dimensional geometries, the definition of contrast is not appropriate, as the maximum and minimum values of intensities may be different at the center, corners, etc. Similarly, edge slope may be different in different planes. Recently, a figure of merit (FOM) has been proposed to evaluate the image quality of two‐dimensional structures by a single parameter. In this paper, both contrast and FOM have been calculated as a function of the parameters of the optical system. It has been shown that in the case of near micron geometries, the variation in the contrast and edge slopes is sometimes misleading, whereas the FOM gives more accurate information of the image fidelity.