Fig. 2. (A) Velocity maps of -actinin-EGFP and mRFP-actin in a MEF cell plated on 1 µg/ml fibronectin. Analysis was performed on 100 frames imaged at 10 seconds per frame. The color-coding for the velocity vectors is universal within the figure with blue being slow velocities and red being faster velocities. The scale of the velocity vectors is different for each plot and is referenced on each image with a 0.5 µm/minute velocity scale arrow. Spatial scale bar is 5 µm. Pixel size is 0.215 µm. (B) Sample STICS correlation function showing that flow-component peak tracking is quite difficult without immobile population filtering (arrowhead). (C) After immobile population removal, a clear displacement of the flow component peak can be observed (white arrowhead) and tracked to reveal the direction and magnitude of the velocity. This filtering removes the contribution to the correlation function of the large static features, i.e. the actin filament structures. Bar, 1 µm.