Figure 3. The experimentally derived optimum persistence time constant as a function of disk diameter for speeds of (a) 6.25 mm s^–1, (b) 12.5 mm s^–1, (c) 20 mm s^–1, (d) 40 mm s^–1 and (e) 75 mm s^–1. The illustrative error bar represents an average standard error estimate for each point.