An experimental study was conducted investigating the effects of colour and brightness contrast, direction of contrast, and 6 contrast values upon the legibility of a circular dial. The brightness of four chromatic hues was matched with four achromatic hues. Hues were combined in all possible combinations excluding chromatic with achromatic, resulting in 6 contrast values. For both dark on light and light on dark contrast directions, the contrast values were equal. Half of the 24 subjects had pilot training and half did not. A Dodge type tachistoscope was used to present the stimulus conditions. Reading time results indicated that the action of colour contrast to a dial of a given achromatic brightness contrast value, with a light on dark contrast direction, will not degrade and may improve the legibility of that dial.
Abstract