Horn and schunck Relatively crude form of numerical differentiation can be source of error Spatiotemporal smoothing Gaussian prefilter with o= 1.5 pixels in space and 1. 5 frames in time 4-point central differences for differentiation mask;(-1,8.0,-81)Horn and Schunck • Relatively crude form of numerical differentiation can be source of error • Spatiotemporal smoothing – Gaussian prefilter with 1.5 pixels in space and 1.5 frames in time • 4-point central differences for differentiation – mask 1 ( 1,8,0, 8,1) 12 − −  =