Effect of field view size and lighting on unique-hue selection using Natural Color System object colors

• Selection of object unique hue (UH) stimuli is apparently affected by field view size.
• Change of illumination conditions influences UH selections of object stimuli.
• Chromatic adaptation and objects color inconstancy account for some of the hue shift.
• Inter and intra-subject variation among subjects is larger in ∼5.7o field of view.
• Intra subject variability in UH selections is ∼19% of inter-subject variability.

The aim of this study was twofold, first to determine the effect of field view size and second of illumination conditions on the selection of unique hue samples (UHs: R, Y, G and B) from two rotatable trays, each containing forty highly chromatic Natural Color System (NCS) samples, on one tray corresponding to 1.4° and on the other to 5.7° field of view size. UH selections were made by 25 color-normal observers who repeated assessments three times with a gap of at least 24 h between trials. Observers separately assessed UHs under four illumination conditions simulating illuminants D65, A, F2 and F11. An apparent hue shift (statistically significant for UR) was noted for UH selections at 5.7° field of view compared to those at 1.4°. Observers’ overall variability was found to be higher for UH stimuli selections at the larger field of view. Intra-observer variability was found to be approximately 18.7% of inter-observer variability in selection of samples for both sample sizes. The highest intra-observer variability was under simulated illuminant D65, followed by A, F11, and F2.