Color perception within a chromatic context: Changes in red/green equilibria caused by noncontiguous light

Light at tke boundary of a ~fo ~ test field ~co~~~) has a qu~~~vely diiferent effect on coIor perception than Iight in more remote ~~g ~ regium (corrtcxt). Basic properties of &or perceptioa with contextual skort-wavelength iight are amessed here with a lo test iieid smrou&d by either contiguous or noncontiguous 440 or 491 nm light (32 td). Contrasting sthnuii are 3 or 5’ adapting iields, a thin lo i,d.-2O o.d. (0.5O wide) contiguous band, or a large lo i.d.-5O o.d. contiguous surround. Contextual stimuii are a remote 3O i.d,-5O o.d. ring or 0.50 wide noncontiguous bauds at various distances from the edge of the lo test field (2 ” i.d.-3O o.d., 30 i.d;-4 ’ o-d., or 4O i.d.-50 o.d. bands). Contiguous surrounds have iittIe influence on color appearance, but remote noncontiguous short-wavelength light strong aifects the color of the test field, shifting it toward redness. The shift toward redness increases as a thin 440 nm band is moved farther from the test field (up to 50), unlike the effect of distance on remote middle- and long-wavelength bands. M easurements comparing the effects of 440 run and lu~na~uat ~ 491 nm light indicate a contribution from S cones. Color appearance Color context Color contrast Induction Color perception Red/green equilibrium Short-wavelength light INTRODUCTlON Local retinal contrast at the boundary of a uniform test field affects perceived color and brightness. These effects are well-documented, and are accounted for by fairly simple models of center-surround interaction (e.g. Brou