In response to Pete Andrews the treatises presented by Hansma, Peterson, Luong et al derive the optimum F-Stop for a given focus spread. The formula is simply fs=(Focus spread * 375) ^ 1/2 . For a symetrical lens(most normal, and moderate wide angle and tele lenses), where the magnification is less then 1/10, maximum sharpness is obtained. The resulting resolution on the film is measured by R=2/(F-Stop/530), and the maximum print enlargement is R/5. If you want maximum PRINT resolution, this is the way to go.