ABSTRACT
The interaction of time and color can be striking. If two quite different colors (such as red and green) are alternated slowly, the change in apparent color is dramatic. Alternatively, if the two colors are alternated rapidly, a single intermediate color appears to be flickering. If in addition the ratio of luminances of the two colored lights is varied, the apparent flicker can be minimized. Typically, flicker is at a minimum for only a very narrow range of luminance ratios. This phenomenon was first exploited as a photometric method a century ago [1] with a technique that has become known as heterochromatic flicker photometry (HFP) [2].
