High Frame Rates and Human Vision: A View through the Window of Visibility

There is new interest in higher frame rates for digital cinema. The frame rate and subsequent processing have a large impact on the presence of artifacts in the final presentation. The structure of these artifacts is revealed by transforming the sequence of frames into the spatiotemporal frequency domain. The visibility of these artifacts can be determined through application of a tool called the window of visibility. This is a simplified representation of human visual sensitivity to spatial and temporal frequencies. This paper describes the capture and display of movies in signal processing terms. It shows how the several steps in the process can by represented in space and time and in spatial and temporal frequency. It then introduces the window of visibility as a simplified version of the human visual contrast sensitivity function. It shows how the tool can be used to compute the lowest artifact-free frame rate under simplified circumstances. It also shows how it can be used to visualize the impact of various steps in processing the image sequence. Finally, the paper describes the influence of luminance, eccentricity, color, and eye movements on the size and shape of the window of visibility. In conclusion, the tool provides a useful aid to understanding the role of human visual sensitivity in the selection of frame rates and frame processing. The paper also provides an interactive demonstration that allows exploration of the trade-offs in movie capture and display.