A new dynamic image processing technique is proposed for measuring the velocity-field of the translational motion of crowded particles. The local velocity at a target pixel-site is estimated by mutual-correlation analysis between the temporal brightness change of the target pixel and that of neighbouring pixels. The next-nearest 16 pixels are selected as the neighbouring pixels in this study. The direction and the speed of the particle motion are evaluated by the mutual-correlation function having maximum value and the lag time of the function, respectively. The usefulness of the proposed technique is examined by a simulation experiment (unidirectional motion) and an actual scene analysis (vortex motion). Obtained velocity-field of these motions are visualized with orientated lines, and the resulting fields are consistent with expected fields.