35-MM FILM SCANNER AS AN INTRAORAL DENTAL RADIOGRAPH DIGITIZER .2. EFFECTS OF BRIGHTNESS AND CONTRAST ADJUSTMENTS

Typical 35-mm slide scanners use a photodiode array and software that allows for digital and analog controls that are manually adjustable. T he digital controls provide brightness and contrast adjustments, where as corresponding analog controls adjust the exposure time and black le vel that determines the clamping level of the charge-coupled device fo r the maximum black in the image. The objective of this study was to d etermine the effects of these controls on the radiometric data of intr aoral dental radiograph images, to establish recommended settings, and to set specific standard guidelines for the digitization process. Thr ee approaches were used. The results of this study demonstrate that br ightness and contrast control alterations on the digitizer produces di fferent optical densities and modulation transfer function values. The impact of these results is unresolved yet must be considered in analy sis on quantitative radiometric studies.