Optimization of the light intensity for Photodetectors calibration

In this article we present an evaluation of the uncertainty in the average number of photoelectrons, which is important for the calibration of photodetectors. We show that the statistical uncertainty depends on light intensity, and on the method of evaluation. For some cases there is optimal light intensity where the accuracy reaches its optimal value with fixed statistics. A method of photoelectron evaluation based on extraction of pedestal's (zero) probability gives best accuracy at approximately 1.6 photoelectrons.