Appendix S1 - Temporal Statistics of Natural Image Sequences Generated by Movements with Insect Flight Characteristics

Time course of first order statistics of the mean brightness and of the root mean square contrast in differently sized image patches during rotational and translational movements (see Appendix S1 for details). Moreover, we examined the spatial frequency statistics within the image patches and, thus, calculated two-dimensional power spectra (Fig. 2D–F), after having tapered the image patches with a sinusoidal window to eliminate boundary effects. Power spectra were calculated by taking the squared magnitudes of fast Fourier transformations (FFTs). Taking the mean over all frequencies for each viewing direction, we obtained the orientation-dependent power spectra (Fig. 2G) providing some information about the orientations of contours that were most prominent in the image. By taking the mean over all orientations for each frequency, we calculated the frequency-dependent power spectra (Fig. 2H). More details are given in Appendix S1. (DOCX)