In this paper we present experimental measurements of optimized rotating retarder systems in the presence of noise and in the presence of experimental error in the angular positioning of the rotating elements. Previous studies have analyzed such effects theoretically and through numerical simulation. Our results agree with the theoretical predictions, but point out several practical factors that affect such systems. These factors include intensity fluctuations that cannot be modeled as additive noise, the balance between noise and error, which have always been considered separately, and the effect of input polarization state on the performance of the polarimeter systems. We present results for both passive (Stokes) and active (Mueller) polarimeters.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.