1. A method for providing an exposure value for radiographic imaging comprising: obtaining a set of flat-field images at two or more exposure values; measuring a noise power spectra using the flat field images; generating at least one noise table according to the noise power spectra interpolated for a set of predetermined exposure values; transforming exposure values of a clinical image to form a reduced exposure simulation image; generating a noise mask according to the at least one noise table and exposure values of the reduced exposure simulation image; adding the noise mask to the reduced exposure simulation image; assessing the reduced exposure simulation image; and generating a preferred dose reduction factor.