Detection of blue under chromatic adaptation: the effects of stimulus size and eccentricity.

We measured thresholds for the perception of blue under chromatic adaptation to white, green, yellow or red at the eccentricities of 0-70 deg in the temporal visual field of four subjects. We used a series of stimulus sizes at each eccentricity, without a prior assumption of any peripheral size-scaling factor. The CIE 1976 UCS (u',v') chromaticity coordinates corresponding to blue perception were subtracted from the chromaticity coordinates of the adaptation field in order to obtain the threshold differences (du',dv') in chromaticity coordinates. Spatial scaling factors for the perception of blue were obtained by non-linear regression (E2 + 5 deg) refers to the eccentricity at which stimulus diameter had to be doubled in order to maintain performance found at the eccentricity of 2.5 deg. E2 for the perception of blue tint varied from 1.2 to 36 deg depending on the state of chromatic adaptation and subject. For the perception of blue tint in yellow three subjects and for the perception of blue tint in red one subject had no spatial scaling factor that would make performance independent of eccentricity. Thus, spatial scaling does not always work.