Fig. 4. Correlation-length analysis. (a-c) Square regions of the images (a) were filtered through Fourier mask (b) to highlight features along one orientation (c). Correlation curves measured along this direction (d, blue) were fitted (d, red) with theoretical correlation function to obtain the correlation length. (e,f) Mean correlation length measured in simulated images (solid lines) varies, depending on the mean filament length, (e) branching angle fluctuation and (f) curvature radius. Curves were compared with experimental correlation length measured in untreated cells (dashed black lines) and in cells treated with cytochalasin D at 0.05 µM (dark gray line) and 0.1 µM (light gray line). (g) Comparison of normalized correlation-length distributions from simulated images with different sets of parameters (colored symbols) to experimental images (black curve).