The authors have earlier found support for the notion that apparent motion (AM) is mediated by a low-pass temporal-frequency filter operating over the spatial domain of the AM sources. Experiments have been carried out to test how this response is changed, or unchanged, through varying the source intensities or contrasts. The results indicate no intensity or contrast effects on the spatiotemporal limits for AM. These results are related to the early formulations of Korte and indicate that there is no amplitude-modulation or contrast-sensitivity function for AM--as there is for threshold movement detection. The filter mechanism seems to be largely restricted to the spatiotemporal domain.