Figure 2. Illustration of the method for deriving the optimum frame averaging time constant. This example is for the 11.1 mm disk diameter moving at 20 mm s^–1. The solid arrow shows the minimum of the curve, taken as the optimum time constant. The curved dashed lines indicate an estimate of the standard error about the cubic curve fit. The resulting estimate of standard error on the optimum time constant is shown by the horizontal error bar.