Beard and Chuang's equilibrium shapes were
calculated using a frame-averaged volume equivalent diameter for
each observed drop at a particular fall distance. The observed drop
shape captured in each frame was then compared with the predicted
shape. Fig. 12 shows the evolution of drop-averaged R2 values from
these comparisons for 2.6, 3.7, and 5.1 mm diameter drops. Here, a
plateau is observed for all three drop sizes studied after some fall
distance. This plateau indicates the establishment of an equilibrium
drop shape and is used to determine the onset of Zone II, which
coincides with the end of Zone I.