RGB 色彩系统能唯一地对应某一种频率的光吗？

RGB并不是一种对颜色的精确描述，想要用这种办法准确描述一种颜色，需要指定某种绝对色彩空间才行。比如某种红色为sRGB或者Adobe RGB描述下的（255,0,0）这样才有意义，单纯说一个RGB值没有任何意义。

详细解释清楚非常麻烦，我尽量简单的说吧。

还是把这张图放上来：

图示为CIE 1931 xy色度图。你可以看到中间彩色部分的边界标记着一些数字，这些是对应单色光的波长。注意这张图只是个示意图，其中带颜色的部分表示人眼能观测到的所有颜色。这些颜色在绝大多数（甚至可以说所有）显示设备中，都没有办法完整表现出来。所以它只是个示意图，不要太较真。

曾经人们做过一系列颜色感知有关的实验，

这里描述了这个实验。它们用了一个屏幕，一边是被测试色彩，一边是三种颜色的光混合出的颜色。通过调整三种光中每种光的不同明度，来得到和另一侧相同的颜色。事实证明人眼并不区分究竟是单色光还是混合光。当某种单色光可以通过这三种颜色的光混合出来时，把这三种光当时的明度记录下来。据此计算出颜色匹配函数。

这里横坐标就是单色光的波长，纵坐标就是合成相同的颜色，所需三种光分别的明度。

这里实验用的三种光波长是特定的。就是第一张图里三角形的三个顶点。三角形内的所有颜色都可以通过这三种波长的光混合而成。基于这三种光构造出的色彩空间就是CIE RGB。其中R,G,B三种光每种都是特定的波长。

但基于三种数值构造出的色彩空间并非只有这一种。类似的还有sRGB和Adobe RGB，他们选择的RGB和CIE RGB是不同的，表示的颜色范围也有所不同。

比如这是sRGB的：

中间那个D65是所谓的白点，我们把它就当成白色。

这里是Adobe RGB，你可以看到它涵盖的颜色要比sRGB更广

说到这里你应该清楚了：

RGB并不是三种确定的颜色，在不同色彩空间中，对于这三种颜色有不同的规定。究竟选择怎样的颜色作为RGB的基础，取决于这个色彩空间的设计目的。比如CIE RGB是基于之前的实验数据，Adobe RGB是为了包含印刷用的全部色彩。而当你选择了某种色彩空间，就相当于选择了如何去用数值抽象的描述一种颜色。

你在很多地方看到的这种舌行的彩图，画的的都是CIE 1931 XYZ色彩空间，包括前面用的三张图都是。这种色彩空间比较特殊，是基于实验直接测定的。因而很多其他色彩空间都是基于它来定义的。只要给出一个转换函数，就能以另外的三种数值来描述一个颜色了。

另外我在这个回答里说了一些不同颜色空间的区别，你也可以参考一下：

以上图像均来自WIKI

不能惟一对应，只能说人眼看单波长光和看 RGB 色感觉是相似的。

"Primary colors are not a fundamental property of light but are related to the physiological response of the eye to light. Fundamentally, light is a continuous

of the

that can be detected by the human eye, an infinite-dimensional

space.

However, the human eye normally contains only three types of color receptors, called

. Each color receptor responds to different ranges of the color spectrum. Humans and other species with three such types of color receptors are known as

. These species respond to the light stimulus via a three-dimensional sensation, which generally can be modeled as a mixture of three primary colors."

"Each different pigment is especially sensitive to a certain

of

(that is, the pigment is most likely to produce a

response when it is hit by a

with the specific wavelength to which that pigment is most sensitive)."

"As an example, suppose that light in the orange range of wavelengths (approximately 577 nm to 597 nm) enters the eye and strikes the retina. Light of these wavelengths would activate both the medium and long wavelength cones of the retina, but not equally—the long-wavelength cells will respond more. The difference in the response can be detected by the brain, and this difference is the basis of our perception of orange. Thus, the orange appearance of an object results from light from the object entering our eye and stimulating the different cones simultaneously but to different degrees.

Use of the three primary colors is not sufficient to reproduce all colors; only colors within the

defined by the

of the primaries can be reproduced by additive mixing of non-negative amounts of those colors of light."

一种任意波长的单色光，作用在视网膜上给人的感觉，是可以通过混合基色光来模拟的，基色不能由其他颜色混合得来。

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RGB 是加色模型的基色，屏幕是从黑色往上加色。

"The choice of primary colors is related to the physiology of thehuman eye; good primaries are stimuli that maximize the difference between the responses of the

of the human retina to light of different wavelengths, and that thereby make a large

.

The normal three kinds of light-sensitive photoreceptor cells in the human eye (cone cells) respond most to yellow (long wavelength or L), green (medium or M), and violet (short or S) light (peak wavelengths near 570 nm, 540 nm and 440 nm, respectively[3]). The difference in the signals received from the three kinds allows the brain to differentiate a wide gamut of different colors, while being most sensitive (overall) to yellowish-green light and to differences betweenhuesin the green-to-orange region."

http://en.wikipedia.org/wiki/RGB_color_model#Additive_primary_colors

"full intensity of each gives a white; the quality of this white depends on the nature of the primary light sources, but if they are properly balanced, the result is a neutral white matching the system's white point."

http://en.wikipedia.org/wiki/RGB_color_model#History_of_RGB_color_model_theory_and_usage

CMY 是减色模型的基色，K 用来控制黑度，印刷只能从白色往外减色。

减色模型不止 CMYK，还有我们美术课用的 RYB/红黄蓝。

http://en.wikipedia.org/wiki/Subtractive_color

"In late 19th and early to mid-20th century commercial printing, use of the traditional RYB terminology persisted even though the more versatile CMY (Cyan, Magenta, Yellow) triad had been adopted"

http://en.wikipedia.org/wiki/RYB_color_model#Modern_understanding

"German and English scientists established in the late 19th century that color perception is best described in terms of a different set of primary colors – red, green, and blue (RGB) modeled through the additive, rather than subtractive, mixture of three monochromatic lights"