Appearance of Maxwell’s spot in images rendered using a cyan primary

Abstract

The discovery of melanopsin as a third type of retinal photoreceptor, contributing to both perceptual vision and reflex light responses, represents a new opportunity to optimise the design of artificial light sources for practical applications and to generate experimental stimuli. In the case of emissive displays, multiprimary designs incorporating a cyan primary could be used to allow melanopic radiance to be controlled independent of colour and luminance. Here we explore the performance a five-primary (violet, cyan, green, yellow, red) display device and find an anomaly in colour appearance when the cyan primary is employed. The anomaly took the form of a reddish/pinkish tinge in the central visual field, consistent with descriptions of Maxwell’s spot. This effect was apparent in some full colour images and in uniform discs over a range of chromaticities. Its appearance in coloured discs correlated with differences in calculated colour coordinate between central and peripheral vision. A simulation indicated that inclusion of any primary with predominant output in the 470–500 nm range has the potential to produce such a discrepancy in central vs peripheral appearance. Applying an additional constraint in colour processing to reproduce naturally occurring differences in central vs peripheral colour coordinate eliminated appearance of the spot and produced acceptable colour images.

Daylights with high melanopsin stimulation appear reddish in fovea and greenish in periphery

“…The visual stimulus of high melanopsin stimulation appears reddish in the foveal vision, which is similar to Maxwell’s spot, an entopic phenomenon that appears as a red spot at the fovea. Maxwell’s spot is related to the difference in tristimulus values between the 10° and 2° CMFs, and a higher cyan primary light is more likely to appear in metameric visual stimuli [ 56 , 57 ]. Although the color appearance model to explain the phenomenon of Maxwell’s spots is unclear, the absorption of light by the macular pigment [ 56 ] and melanopsin stimulation [ 57 ] may be involved.…”

“…Maxwell’s spot is related to the difference in tristimulus values between the 10° and 2° CMFs, and a higher cyan primary light is more likely to appear in metameric visual stimuli [ 56 , 57 ]. Although the color appearance model to explain the phenomenon of Maxwell’s spots is unclear, the absorption of light by the macular pigment [ 56 ] and melanopsin stimulation [ 57 ] may be involved. The visual stimuli with high melanopsin stimulation used in the current study were spectral power distributions with a high cyan component.…”

Melanopsin-mediated amplification of cone signals in the human visual cortex

“…As such, these measured contrast imperfections are smaller than can be detected in an ERG recording [ 10 , 37 , 40 – 43 ], and at such levels, their magnitude is too low to modify cone-mediated visual thresholds [ 19 ]. Accordingly, none of our observers reported the appearance of Maxwell's spot [ 44 ] or a Purkinje tree [ 39 ], with the orangish appearing background [ 44 , 45 ], and with the balanced rod activity across the central and peripheral visual field [ 46 ].…”

Melatonin suppression does not automatically alter sleepiness, vigilance, sensory processing, or sleep

“…Values were calculated using the luox app (Spitschan, 2021). A white background with a black spot in the centre subtending to a visual angle of 8.6° was presented on the screen to avoid a phenomenon called Maxwell's spot, a red spot appearing in the centre of the visual field due to the absorption of light by the macular pigment (Spitschan, Jain, Brainard, & Aguirre, 2014;Gardasevic, Lucas, & Allen, 2019;Isobe & Motokawa, 1955). In the middle of the black circle, there was a small white circle, which served as a fixation point and subtended to a visual angle of 0.5°.…”