Pastilha Ruben, Gupta Gaurav, Gross Naomi, Hurlbert Anya
Neuroscience, Institute of Biosciences, Newcastle University, Newcastle upon Tyne, UK.
J Vis. 2020 Dec 2;20(13):18. doi: 10.1167/jov.20.13.18.
Temporal changes in illumination are ubiquitous; natural light, for example, varies in color temperature and irradiance throughout the day. Yet little is known about human sensitivity to temporal changes in illumination spectra. Here, we aimed to determine the minimum detectable velocity of chromaticity change of daylight metamers in an immersive environment. The main stimulus was a continuous, monotonic change in global illumination chromaticity along the daylight locus in warmer (toward lower correlated color temperatures [CCTs]) or cooler directions, away from an adapting base light (CCT: 13,000 K, 6500 K, 4160 K, or 2000 K). All lights were generated by spectrally tunable overhead lamps as smoothest-possible metamers of the desired chromaticities. Mean detection thresholds (for 22 participants) for a fixed duration of 10 seconds ranged from 15 to 2 CIELUV ΔE units, depending significantly on base light CCT and with a significant interaction between CCT and direction of change. Cool changes become less noticeable for progressively warmer base lights and vice versa. For the two extreme base lights, sensitivity to changes toward neutral is significantly lower than for the opposite direction. The results suggest a "neutral bias" in illumination change discriminability, and that typical temporal changes in daylight chromaticity are likely to be below threshold detectability, at least where there are no concomitant overall illuminance changes. These factors may contribute to perceptual stability of natural scenes and color constancy.
光照的时间变化无处不在；例如，自然光在一天中色温与辐照度都会发生变化。然而，人们对人类对照明光谱时间变化的敏感度知之甚少。在此，我们旨在确定沉浸式环境中日光同色异谱色的最小可察觉色度变化速度。主要刺激是全局照明色度沿着日光轨迹朝着更暖（朝着更低相关色温 [CCT]）或更冷方向，远离适应基础光（CCT：13000K、6500K、4160K 或 2000K）进行连续、单调的变化。所有灯光均由光谱可调的顶灯产生，作为所需色度尽可能平滑的同色异谱色。对于固定的 10 秒持续时间，22 名参与者的平均检测阈值范围为 15 至 2 CIELUV ΔE 单位，这显著取决于基础光 CCT，并且 CCT 与变化方向之间存在显著交互作用。对于逐渐变暖的基础光，冷变化变得不太明显，反之亦然。对于两种极端基础光，对朝着中性方向变化的敏感度显著低于相反方向。结果表明在照明变化辨别能力方面存在“中性偏差”，并且日光色度的典型时间变化可能低于阈值可检测性，至少在没有伴随整体照度变化的情况下是这样。这些因素可能有助于自然场景的感知稳定性和颜色恒常性。
