Fig. 4. Characterization of flash-induced photophobic responses of individual cop^d mutant cells. Average actual speed changes of individual cells after application of light flashes with different intensities (100, 10, 1 and 0.1%). The observed maximal speed reduction (v) was plotted versus the photon exposure (Q). No intensity dependent differences in the stop response are observed between wt (CC2454) and cop^d35 (opsin content <5%).