Color supports object identification. However, two objects that differ in color under one light can appear indiscriminable under a second light. This phenomenon, known as illuminant metamerism, underlies the difficulty faced by consumers of selecting matching fabric or paint colors in a store only to find that they appear not to match under home lighting. The frequency of illuminant metamerism has been evaluated only under single, uniform illuminants. However, in real world conditions, the spectral content of light falling on an object varies with direction (Morimoto et al. 2019), meaning that a surface will sample different spectra depending on its angle within the environment. Here we used computer-graphics techniques to simulate a pair of planar surfaces placed under newly measured hyperspectral illumination maps that quantify the directional variability of real-world lighting environments. We counted the instances of illuminant metamerism that can be solved simply by viewing surfaces tilted to a different direction. Results show that most instances of illuminant metamerism can in theory be resolved for both trichromatic and dichromatic observers. Color deficient observers benefit more than trichromats implying that the directional variability allows the recovery of the missing dimension in their colour vision systems. This study adds a new perspective to the classic trichromatic theory of human vision and emphasizes the importance of carefully considering the environments in which biological vision operates in daily life. It is striking that the physical directional variability available in natural lighting environments substantially mitigates the biological limitations of trichromacy or dichromacy.

中文翻译：

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你能看到多少种颜色？真实的环境照明提高了表面颜色的辨别力

颜色支持对象识别。然而，在一种光线下颜色不同的两个物体在第二种光线下可能显得无法区分。这种现象被称为光源同色异谱，它是消费者在商店中选择匹配的织物或油漆颜色时所面临的困难的根源，结果却发现它们在家庭照明下看起来不匹配。仅在单一、均匀的光源下评估光源同色异谱的频率。然而，在现实条件下，落在物体上的光的光谱内容随方向而变化（Morimoto et al. 2019），这意味着表面将根据其在环境中的角度对不同的光谱进行采样。在这里，我们使用计算机图形技术来模拟放置在新测量的高光谱照明图下的一对平面，这些平面可以量化现实世界照明环境的方向变化。我们计算了光源同色异谱的实例，这些实例可以通过简单地通过观察倾斜到不同方向的表面来解决。结果表明，理论上三色和二色观察者都可以解决大多数光源同色异谱的情况。色觉缺陷的观察者比三色视觉者受益更多，这意味着方向可变性可以恢复其色觉系统中缺失的维度。这项研究为人类视觉的经典三色理论增添了新的视角，并强调了仔细考虑生物视觉在日常生活中运作的环境的重要性。令人惊讶的是，自然光环境中可用的物理方向可变性大大减轻了三色性或二色性的生物限制。