What happens to color perception in low light? Previous research has shown that the brightness of color is directly related to the color of the object. The present experiment was designed to test the ability of individuals to identify the colors red, blue, green, and yellow in low light levels. In this experiment the light levels in the laboratory were varied while subjects were presented with stimuli of different colors. This was done in order to find a threshold that could be generalized for these colors.
Methods
Our experiment used twenty Alma College students (ten men and ten women) as subjects, individually tested.
A light meter (photometer) was used to measure light intensity at different levels. These levels were marked on the dimmer light dial. Each increment was equal and was represented by a number (example: 1, 2, 3, etc.).
Each subject was seated eight feet two inches in front of a white board. The lights were turned off, and the subject was presented with the first color on the white background. The light intensity was then increased by one increment at a time, until the subject could identify the color of the chip. The light intensity was recorded and the lights were raised to full intensity to counteract dark adaptation. This process was repeated for each color card, in random order, for a total of sixteen trials. Munsell color chips were used on the background. The value/chroma is shown in Table 1. (See Table 1.)
Table 1.Hue, value/chroma of each color.
Results
The color red was identified with the lowest mean light level in this study. The mean level of the room's light intensity during a red trial was .22 foot candles. Yellow was identified correctly at a mean light level of .25 foot candles. Green's average light level was .35 foot candles, and blue, .39 foot candles. (see Figure 1.)
Figure 1. Mean light level in foot candles of each color hue when subjects responded correctly.
Yellow was the most accurately perceived color, with only one incorrect response out of 80 total responses. Responses to red were incorrect in five of the total responses. 24 responses to blue were incorrect. Green was the least accurately perceived, with 35 of the 80 responses incorrect. (See Figure 2.)
Figure 2. Number of incorrect subject responses to each hue.
When subjects incorrectly responded to green, their responses were: blue 33 times, red 1 time, and yellow 1 time. When subjects incorrectly responded to blue, their responses were: green 19 times, and red 4 times. When subjects incorrectly responded to red, their responses were: green 1 time, and yellow 4 times. When subjects incorrectly responded to yellow, their responses were: red 1 time.
Discussion
The conclusions that can be drawn from these findings are quickly apparent. While yellow was the color most accurately identified in low light, red was the color that was identified at the lowest average light level. Both green and blue were much more difficult to identify in low light, and more difficult to identify as their respective color. Subjects noted that they were able to see the color chip, but were unable to decide if the color was green or blue (having only those choices as "dark" colors).
If there is an application where the ability to accurately perceive the color of an object is essential, the data from this study suggests that the color used should be yellow. If a color is needed that can be perceived at a low light level, the data from this study suggest that red is used.
Further research in this area could include the use of a black background to mount the color chips on. This would be used along with some trials that did not have a color chip on the background, and therefore, were completely black. This would more accurately represent low light level situations.
The results from a study such as mentioned above would likely include a much lower mean light level for yellow, and a higher mean light level for green and blue.