Dynamic Vision—The Legibility of Equally Spaced Alphanumeric Symbols 1

Abstract

A. trial study was conducted on the ability of observers to identify moving targets consisting of alphanumeric symbols. The targets, randomly assigned, were regularly spaced on an endless belt which was viewed from a constant distance. The target subtended an angle of 39 min. The space between targets subtended an angle of 51 min. The targets moved vertically from top to bottom in the frontal plane. Six subjects were tested on criteria of zero legibility and 100 per cent legibility when the targets were viewed through apertures 2 in. wide and 2 in., 8 in., and 20 in. high.

Performance was measured in terms of the angular velocity of the targets past the observer's eyes. As aperture height increased both legibility criteria could be met at higher angular velocities of the stimulus materials. The mean angular velocities for the zero legibility criterion were approximately three times as great as for the 100 per cent legibility criterion.

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