A broad range of element size, element shape, and interelement spacing/element size ratio combinations at high and low ambient illuminance levels was used to determine optimal combinations for a 5 X 7 dot matrix visual display. Three tasks - a reading test, a random search task, and a structured (menu) search task - were used to enhance the utility of the research. All tasks were displayed on a CRT display 1.02 m from the subject.
There were different overall results for the reading and the search tasks, as shown by an analysis of variance. The smaller elements (0.76 and 1.14 mm) and the 0.5 space/size ratio produced the shortest reading times, while the shortest search times came from the larger elements (1.14 and 1.52 rum). The square shape and low illuminance level (5.4 lux) had the shortest times for all three tasks.
For a general purpose display, the combination of a square 1.14 rum dot, with 0.57 mm edge-to-edge spacing is recommended, to be used with the lowest practical ambient illuminance.
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