Color Perception in Peripheral Vision under conditions of Rapid Light Adaptation
According to Stabell and Stabell (1982) color vision deteriotes as the stimulus is moved further into the peripheral field. In the same study, some visible spectrum wavelengths (colors) were perceived as different a color than their agreed norm. This false perception was dependent on the angle in the field, and the field in which the stimulus was presented. In a somewhat similar study, Nagy and Wolf (1993) reaffirmed that stimulus size also had an effect on the perception of color. The present study will combine these findings with the addition of rapid light adaptation. It is expected that the rapid adaptation will increase the liklihood of false identification and decrease the angle of perception.
Method
Apparatus
A retinal focusing apparatus which included a small mirror, and a semicircular angle marker (see above picture). Munsell color chips of the following designations:
- 7.5Y, 8.5/10 - Yellow
- 7.5G, 4/10 - Green
- 7.5B, 4/10 - Blue
- 7.5R, 4/14 - Red
- 7.5P, 4/10 - Purple
A photometer was also used to measure light levels, as well as small tweezers to hold the stimuli without the presence of the experimenter's fingers.
Subjects
A convenience sample of eight subjects was used to gather the data for this study. All but one subject was an aquantaince of the experimenter. Only one potential subject was ommitted due to color-blindness.
Technique
Prior to running the study the five colors and the two conditions were randomized. The randomization produced the following sequence in which the study was run.
- Light - Red
- Light - Blue
- Dark - Green
- Dark - Yellow
- Light - Purple
- Dark - Blue
- Light - Yellow
- Dark - Red
- Dark - Purple
- Light - Green
The light levels were measured to be approximately 0.09 foot candles (fc) for the dark condition and 4.30fc for the more lighted condition.
Using a retinal focusing apparatus, the subject was asked to focus their eye in the small mirror attached to the equipment. The light level was then adjusted to the proper setting. Beginning at 90 degrees temporal, the stimulus was moved foveal in 5 degree increments until the subject correctly identified the color. This procedure was then repeated for the next stimulus.
Results
As expected some colors were more easily perceived dependent on the condition in which it was presented. However, the Red stimulus apeared to show little or no variation for all subjects. The Blue and Yellow stimuli also varied only slightly among subjects in the lighter condition. However, Blue was often perceived as Green in the dark condition, and vice versa. Often Green was not correctly perceived until at least 50 degrees in the temporal field, in two cases it was not perceived at all.
| Condition/Color |
Min. Perception Angle |
Max. Perception angle |
Mean Angle of Perception |
Range (max - min, all Ss) |
| Dark Red |
90 |
70 |
82.5 |
20 |
| Dark Blue |
90 |
0 |
48.75 |
90 |
| Dark Green |
50 |
0 |
20 |
50 |
| Dark Yellow |
80 |
0 |
45.63 |
80 |
| Dark Purple |
80 |
0 |
33.75 |
80 |
| Light Red |
90 |
70 |
86.25 |
20 |
| Light Blue |
90 |
70 |
85.63 |
20 |
| Light Green |
90 |
25 |
71.88 |
65 |
| Light Yellow |
90 |
80 |
84.38 |
10 |
| Light Purple |
85 |
25 |
68.13 |
50 |
Table A. Perception angle data for all subjects.
Figure 1. Mean perception angles for Five Colors under Light and Dark Conditions.
Discussion
According to the data, human vision requires less adaptation time for color perception in lighter conditions. However, human vision was intended for light, and the better vision may be related to more light being reflected off the stimulus. On the contrary however, testimony from subject provided evidence of a fading effect during the first few seconds of the light condition. For example, Yellow was seen as white, blue as turquise, etc.
The opposite was true for the darker condition. Subjects used modifiers such as Dark Red, or Navy Blue, when describing the colors. Also, under the darker condition subjects viewed the Green stimlus as Blue until approximately the 50 degree mark, at which point it suddenly turned Green.
The most likely explanation for the effects of peripheral vision is physiology, however due to time constraints, physiology was not explored in this study.
Although precautions were taken to make the enviroment as neutral as possible, some aspects may have hindered, or altered color perception. For instance, the room in which the study took place was metallic grey, and may have affected the blue and green perception the most. Also, the subjects tended to get frustrated when they could not perceive the color immediatly. This led to one subject stating that he guessed at the Green stimulus (he guessed wrong however).
Overall the data proved that color perception in the peripheral field is dependent on at least three variables, and possibly more. The three variables that seem to play the largest role are light level, angle, and according to Nagy and Wolf (1993), size.
References
- Nagy, Allen L., Wolf, Steven. (1993). Red - Green Color Discrimination in Peripheral Vision. Vision Research, 33, 235-242.
- Stabell, Bjorn., Stabell, Ulf. (1982). Color Vision in the Peripheral Retina Under Phototopic Conditions. Vision Research, 22, 839-844.
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