The utilization of the Bartley effect for the improvement of readability under conditions of low contrast was investigated. A reading chart with gradually decreasing brightness contrast was read under steady and flicker conditions with four different light-dark ratios and two flicker frequencies (9 and 15 cps). The number of lines read was accepted as index of readability and, in a more general way, as index of visibility under low |D^BL)/L conditions. It was found that the effect of flicker was to lower the number of lines read especially at low illumination levels. For this reason it seems doubtful that flicker can be used for the improvement of visibility under conditions of low contrast."
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