Fig 1.
Schematic diagrams of the experimental system.
(A) Plan of the experimental space. The visual stimuli were displayed using a multispectral light source. The light originating from the multispectral light source was controlled via a laptop which was located outside the experimental room. Participants were placed in a dark room and asked to observe visual stimuli with the right eye. The head was stabilized with a chin rest. (B) Visual stimuli from the participants’ perspective. The left image shows the view in the foveal vision; the right image shows the view in the peripheral vision. The white circle of each image is the visual stimuli and the red circle is the fixation point. The size of the white circle is 1.4°, and that of the red one is 0.4°. (C) Perth diagram of the experimental space. Visual stimuli were set for the foveal condition. The line of sight of the right eye was checked by the camera. The left eye was occluded by a light-shielding plate to prevent light from entering the eye.
Fig 2.
The melanopsin stimulation in the experimental conditions.
The relationship between the correlated color temperatures (CCTs) and action factors of melanopsin in several light sources, including the visual stimuli. The reference illuminants are blackbody radiation and CIE daylights. The general illuminants are commonly-used light sources, such as fluorescent lamps and light-emitting diodes (LEDs). The experiment involved four CCT conditions: four in which the stimulation three levels of melanopsin were modulated and the tristimulus values were constant.
Fig 3.
Spectral power distributions of visual stimuli measured using a spectroradiometer.
The visual stimulus was generated with a multispectral light source and was presented as a circular transmitted light-emitting uniform surface with a visual angle of 1.4° using a diffuser.
Table 1.
Measured values of the visual stimuli.
Fig 4.
Presentation sequences in the foveal and peripheral vison conditions.
(A) Foveal vision. (B) Peripheral vision.
Fig 5.
Pie charts were plotted with the results of foveal and peripheral vision in each of the correlated color temperature (CCT) conditions (2700, 5000, 6500, and 8000 K).
The left and right graphs show the results of the high (1,200 cd/m2) and low (55 cd/m2) luminance conditions. The sizes of the pie charts indicate saturation; each portion represents the color components (red, green, yellow, blue) of the elemental color-scaling. The “-,” “none,” and “+” labels correspond to half-, equal-, and two-fold values of melanopsin stimulation based on the reference illuminants of each CCT condition. The “F” and “P” denote foveal and peripheral vision.
Fig 6.
Response results of the elemental color-scaling for eight participants in the foveal vision condition.
The correlated color temperatures (CCTs) of the visual stimuli are (A) 2700 K, (B) 5000 K, (C) 6500 K, and (D) 8000 K. The vertical axis represents the +red-green component and the horizontal axis represents the +yellow-blue component. The symbols indicate the conditions of the visual stimuli; the inverse triangle, circle, and standard triangle indicate half-, equal-, and two-fold of the values of melanopsin stimulation based on the reference illuminant of each CCT. “High” and “Low” in the legends denote high (1,200 cd/m2) and low (55 cd/m2) luminance conditions, respectively.
Table 2.
Bayesian analysis of variance (ANOVA) conducted on the responses of elemental color-scaling (red-green and yellow-blue responses) in foveal vision.
Fig 7.
Response results of the elemental color-scaling for eight participants in the peripheral vision condition.
The correlated color temperatures (CCTs) of the visual stimuli are (A) 2700 K, (B) 5000 K, (C) 6500 K, and (D) 8000 K. The vertical axis represents the +red-green component and the horizontal axis represents the +yellow-blue component. The symbols indicate the conditions of the visual stimuli; the inverse triangle, circle, and standard triangle indicate half-, equal-, and two-fold of the values of melanopsin stimulation based on the reference illuminant of each CCT. “High” and “Low” in the legends denotes high (1,200 cd/m2) and low (55 cd/m2) luminance conditions, respectively.
Table 3.
Bayesian analysis of variance (ANOVA) conducted on the responses of elemental color-scaling (red-green and yellow-blue responses) in peripheral vision.