Stray Light And Shading Reduction In Digital Photography - A New Model And Algorithm

In optical imaging systems, specifically digital cameras, part of the incoming light flux is misdirected to undesired locations due. to scattering, undesired reflections, diffraction and lens aberrations. The portion due mainly to scattering and undesired reflections is called stray light. Stray light reduces contrast and causes color inaccuracy in images. The point spread function (PSF) model for stray light is shift variant and has been studied by Jansson et al. (1998) and Bitlis et al. (2007). In this paper, we keep the model's shift variant nature and improve it by first normalizing it and then incorporating the shading effect inherent in the optical system. We then develop an efficient method to estimate the model parameters by using a locally shift invariant approximation. Finally, we reduce the stray light by deconvolution. We conducted extensive experiments with two camera models. Results from these experiments show the reduction of stray light and thus the improvement of image quality and fidelity.