Abstract
Our recent work on subjective red/green balances of targets that vary along the blue/yellow color axis showed that the amount of S-cone activity in a target would differentially shift their perceived red/green balance point when presented with a black surround compared to a white surround such that targets with low S-cone activity (yellow) showed large shifts in their red/green balance point between the two surrounds and high S-cone activity targets (blue) showed little to no shift (DeLawyer et al., JOSA A, 2018). However, when using surrounds with identical luminance and L/M-cone activity that varied only in S-cone activity we found no differential effect (blue and yellow targets shifted by the same magnitude). This suggested that luminance contrast between white and black surrounds, and not S-cone contrast was the main factor driving the differential red/green balance shift in blue/yellow spectrum targets. However, one other aspect that varies between white and black surrounds is L/M activity. In a series of experiments using surrounds that were white, black, red, green, blue, or yellow; and composed to vary in either luminance, L/M balance, S-cone activity, or some combination of the two, I tested the possibility of surround L/M contrast playing a role in the aforementioned differential surround contrast effect. I found that L/M contrast with the surround creates a powerful differential effect very similar to that seen with white and black surrounds. This effect occurs in addition to that of luminance contrast suggesting both work together to create the differential red/green balance shift.