PTV( Particle Tracking Velocimetry) is applied to images with moving particle images. Properties required for image sensors to analyze movements of scattered particles are discussed. Much higher frame rate than 30 pps is essential, which is realized by parallel readout architecture. Lower descretization level and image compression effectively work to keep both high frame rate and high spatial resolution (number of pixels) for a given number of readout lines. 1) The optimum descretization level for PTV is 4 to 6 bit: 2) Image compression schemes generate weak false particle images, which can be compensated by post-processing if the scheme is not complicated.