Results for the calibration and testing of a 16‐beam grating‐based division‐of‐amplitude photopolarimeter, that take into account the effect of source polarization and imperfections of the polarization state generator, are presented. A model is developed to analyze the elements of the instrument matrix obtained from calibration. The experimental results are compared with the predictions of the model, and useful information is extracted about the optical elements of the system. ©1995 American Institute of Physics.