An apparatus and a method for optimizing the quality of electrophotographic imaging based on the properties of the printing media are presented. In order to determine the properties of the printing media without interrupting the normal image transfer process, the present invention uses rollers as a part of a sensor. When the printing media lies between the rollers, the rollers and the printing media form an RC circuit. A pulse is applied to the RC circuit, the step response of which is periodically sampled. The samples may be obtained logarithmically in time. Based on the resultant response, a controller calculates the resistance and the capacitance of the printing media and adjusts imaging parameters, such as the transfer bias voltage, for optimal image transfer. The entire optimization process occurs between the time the printing media passes through the rollers and the time the imaging transfer is executed.