This note considers the problem of minimizing the computation time required for digital filtering of pictures by the technique of sectioning. Direct enumeration on a computer was used to tabulate the optimum section size, and tables of the optimum section sizes are presented. The tables are compared with previously tabulated optimum sections for one-dimensional filtering; the optimal two-dimensional section sizes have linear dimensions twice as great as the optimal one-dimensional sections. To explain this discrepancy, analytical models are developed for the optimum one-and two-dimensional sections. The analytical models verify the tabulated data on optimum section size, and demonstrate why optimal two-dimensional sections are greater in size than corresponding one-dimensional sections.