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Window of visibility: a psychophysical theory of fidelity in time-sampled visual motion displays

Many visual displays, such as movies and television, rely on sampling in the time domain. We derive the spatiotemporal-frequency spectra for some simple moving images and illustrate how these spectra are altered by sampling in the time domain. We construct a simple model of the human perceiver that predicts the critical sample rate required to render sampled and continuous moving images indistinguishable. The rate is shown to depend on the spatial and the temporal acuity of the observer and on the velocity and spatial-frequency content of the image. Several predictions of this model are tested and confirmed. The model is offered as an explanation of many of the phenomena known as apparent motion. Finally, the implications of the model for computer-generated imagery are discussed.