Abstract
A unique calibration equation for all radiochromic film types is proposed. The determination of this equation comes from an analogy that the authors made between the radiochromic and photographic processes. Photography dynamics is ruled by a differential equation, the logistic equation, describing phenomena of growth versus competition. A solution of the logistic equation is the Green-Saunders equation which was used for the first time by the same authors in a previous referred work for the calibration of a set of EBT3 Gafchromic films. Since this equation has a fundamental physical interpretation, the fitting parameters also represent important physical quantities and two of them in particular fix the film dynamics; one being the contrast and the other the abscissa of the inflection point of the sensitometric curve. In order to show the validity of this approach for more than one radiochromic film type, two sets of radiochromic films, the B3 and HD-V2 Gafchromic films were exposed to several known doses and the Green-Saunders equation was found to perfectly fit the experimental data. A comparison with the same procedure used for EBT3 Gafchromic films is proposed. The findings of this work are an important step forward in the understanding of an interesting and widely used dosimetry technique.