There are two types of light detectors in the human retina, rods and cones. Cones perform best in daylight conditions, whereas rods are specialized for night vision. In the daylight, humans are able to perceive color. This is because there are three different types of cones, each picking up on different spectrums of color (blue, green, and red). At night, human color perception is relatively impaired.
This study focuses on how the cones and rods operate under less than ideal conditions; conditions where both rods and cones are detecting light at the same time but neither detector is operating at its best. Such lighting conditions would be comparable to those experienced at dawn or dusk. The reason for this study is that for many years it has been assumed that rods do not contribute to our ability to perceive color, even under conditions where both rods and cones are detecting the presence of light. It is now known that rods alter color perception, so the color of an object seen under daylight conditions may not be the same as the color seen at dawn or dusk. When color is used to convey information, but lighting conditions under which the color is viewed are changing, the information provided by color may not be accurate. The goal of this study is determine under what conditions failures in color perception arise and how the visual system may compensate for these failures. The results from this project may be applied to the design of color monitors, the efficacy of color information dissemination, and the design of cockpit and/or video displays.