Fig. 10. Deviation of measured, absolute stroke amplitude between both wings from the numerical model, which predicts the wing motion required to compensate for the velocity bias. Object orientation and optomotor experiments using low (high) contrast patterns are plotted in black and red (blue), respectively. Mean minimum deviation at 520 pNm s damping coefficient amounted to approximately 6°, while the animals responded to the bias applied to the high-contrast background (blue). Values are means ± s.e.m., N=24 (black), N=8 (red) and N=15 flies (blue).