Recent revitalization of interests in applying speckle techniques gives rise to the concern of measurement accuracy. In
particular, speckle contrast, an important metric in numerous optical techniques, is affected by many factors related to
light sources, propagation media, and receivers. As a result, proper experimental design is required to minimize
measurement errors. This article considers errors introduced by the discrepancy of incidence and observation angles, by
the limited number of available speckles, and by intensity saturation.