Optimal colours for human vision occur on the boundary of a three‐dimensional object‐colour solid, and result from optimal reflectance spectra that take on only the values 0 and 1, with at most two transitions between those values. Different illuminants lead to different solids. If there are two illuminants and a single sensing device, then we can construct a six‐dimensional double object‐colour solid by concatenating colour signals from both illuminants. Colours on the boundary of a double‐object solid, and the spectra that generate them, can also be called optimal. This article shows that, while optimal spectra for double solids take on only the values 0 and 1, there is no maximum number of transitions between those values: given a device, we can always construct two illuminants such that the resulting double object‐colour solid has an optimal reflection spectrum with as many transitions as desired.

中文翻译：

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双目标色固体的最佳光谱

人类视觉的最佳颜色出现在三维对象颜色实体的边界上，并且是由最佳反射光谱产生的，该光谱仅具有0和1值，并且这些值之间最多有两个过渡。不同的光源导致不同的固体。如果有两个光源和一个传感设备，那么我们可以通过串联来自两个光源的颜色信号来构造一个六维双对象颜色实体。双对象实体边界上的颜色以及生成它们的光谱也可以称为最佳颜色。本文表明，虽然双固体的最佳光谱仅采用值0和1，但在这些值之间没有最大的跃迁数：给定设备，