[en] Two measures (not independent) of radiographic image quality are contrast and spatial frequency response. At normal radiographic exposure levels, noise is not a significant factor in evaluating these parameters. However, when the photon fluence on the detector is less than 100 photons/pixel, the statistical noise in the image significantly degrades the image contrast. This paper presents a method of characterizing the image quality that utilizes both contrast and noise by calculating the net information content of the image (in bits) using the image entropy. An algorithm for calculating information content (IC) is developed and results are presented for simulated radiographs as various radiographic parameters are varied. This Mathematica code is listed in the Appendix. A copper step wedge is radiographed and the actual IC is measured for all the steps which are taken two at a time. This experimental data is compared to simulated results with good agreement. A companion report will show how varying such radiographic parameters as x-ray energy and total dose affect the IC of the image