This work devotes to the optimization of digital X ray transmission radiography for the observation of time dependent processes using a single X-ray photon counting pixel device. The maximization of frame rate of acquired roentgenograms is crucial for this purpose. The influence of the X ray tube voltage on exposure time, which is necessary for sufficient quality of roentgenograms, was investigated. Roentgenograms are distorted due to non uniform pixel detection efficiency across the X ray detector. Such distortion can be successfully eliminated by the proposed “Direct thickness calibration method” regardless of X ray beam hardening, which is due to the variation of inspected body absorption.