How we see color - Colm Kelleher

我们如何看到颜色 - Colm Kelleher

Translator: Andrea McDonough Reviewer: Bedirhan Cinar

翻译人员: Minji Seo 校对人员: Ying Wang

You might have heard that light is a kind of wave

你可能听过光具有波动性，

and that the color of an object

而物体的颜色取决于

is related to the frequency of light waves it reflects.

该物体反射出光线的频率

High-frequency light waves look violet,

高频率的光波看起来是紫色，

low-frequency light waves look red,

低频率的光波看起来是红色，

and in-between frequencies look yellow,

而且两者中间的频率看起来可能是黄色、

green,

绿色、

orange,

橘色

and so on.

等颜色

You might call this idea physical color

你可以说这是物理性的颜色，

because it says that color is a physical property of light itself.

因为它表示光的颜色源自于本身属性

It's not dependent on human perception.

和人类解读能力没有关系

And, while this isn't wrong,

虽然这并非错误，

it isn't quite the whole story either.

但是不能完全解释人如何辨别颜色

For instance, you might have seen this picture before.

举例而言，你可能看过这张图

As you can see, the region where the red and green lights overlap is yellow.

如你所见，红色和绿色光叠加看起来是黄色

When you think about it, this is pretty weird.

但如果你仔细思考，就会觉得怪怪的

Because light is a wave, two different frequencies

因为光具波动性，两种不同频率的光波

shouldn't interact with each other at all,

不应该会有交互作用，

they should just co-exist

它们应该像是合唱演出般

like singers singing in harmony.

共同存在

So, in this yellow looking region,

所以，在你看起来是黄色的区域

two different kinds of light waves are present:

有两种光波存在：

one with a red frequency,

一种是红光光波

and one with a green frequency.

另一种是绿光光波

There is no yellow light present at all.

但这里并无黄光光波的存在

So, how come this region,

那为什么这个

where the red and green lights mix,

红色和绿色迭加的区域

looks yellow to us?

看起来会是黄色呢？

To understand this, you have to understand a little bit about biology,

要了解这个现象，必须先了解生物学

in particular, about how humans see color.

尤其是关于人如何看到颜色的部份

Light perception happens in a paper-thin layer of cells,

光由人类眼球底部

called the retina,

薄薄一层

that covers the back of your eyeball.

被称为视网膜的细胞所接收

In the retina, there are two different types of light-detecting cells:

在视网膜上有两种感光细胞

rods and cones.

杆状细胞和锥状细胞，

The rods are used for seeing in low-light conditions,

其中杆状细胞在低亮度时 负责接收，

and there is only one kind of those.

而且只有一种

The cones, however, are a different story.

而锥状细胞就有所不同了！

There three kinds of cone cells that roughly correspond

我们有三种锥状细胞，

to the colors red,

他们分别对应红色、

green,

and blue.

绿色、

和蓝色

When you see a color,

当你看到颜色时，

each cone sends its own distinct signal to your brain.

不同的锥状细胞会将不同的讯息送向脑部

For example, suppose that yellow light,

举例而言，

that is real yellow light, with a yellow frequency,

当有一道真正具有黄色频率的光线

is shining on your eye.

射入你眼睛时，

You don't have a cone specifically for detecting yellow,

你并没有专门负责接收黄光的锥状细胞

but yellow is kind of close to green

但是因为黄色和绿色

and also kind of close to red,

及红色相近，

so both the red and green cones get activated,

所以负责红色和绿色的锥状细胞会被活化，

and each sends a signal to your brain saying so.

分别传送讯息到你的脑部

Of course, there is another way to activate

当然，有另一种方式可以达到相同效果：

the red cones and the green cones simultaneously:

红色和绿色光同时抵达，

if both red light and green light are present at the same time.

造成负责红色和绿色的锥状细胞同时被启动

The point is, your brain receives the same signal,

这时候脑部会收到相同的讯号，

regardless of whether you see light that has the yellow frequency

不论是接受一束黄光

or light that is a mixture of the green and red frequencies.

或是由红光和绿光所混成的光线都是一样

That's why, for light, red plus green equals yellow.

所以对光线来说，红色加绿色就成了黄色

And, how come you can't detect colors when it's dark?

那为何你无法在黑暗中辨别色彩呢？

Well, the rod cells in your retina take over

这是因为在低亮度的状况下

in low-light conditions.

是由视网膜上的杆状细胞接手感光

You only have one kind of rod cell,

但是你只有一种杆状细胞，

and so there is one type of signal

所以它只能送出一种讯号

that can get sent to your brain:

告诉你的大脑

light or no light.

是亮还是暗

Having only one kind of light detector

因为只有一种侦测器，

doesn't leave any room for seeing color.

所以没办法侦测看到的颜色

There are infinitely many different physical colors,

物理颜色近乎无限多种，

but, because we only have three kinds of cones,

而我们只有三种锥状细胞，

the brain can be tricked into thinking it's seeing any color

大脑则藉由运算

by carefully adding together the right combination

红、绿、蓝

of just three colors:

这讯号强弱相加的结果

red, green, and blue.

让我们看到不同色彩

This property of human vision is really useful in the real world.

人类视觉原理在真实世界中十分有用

For example, TV manufacturing.

例如：电视机的制造

Instead of having to put infinitely many colors in your TV set

与其要放进无限种颜色的光源

to simulate the real world,

以仿真真实世界的色彩

TV manufacturers only have to put three:

电视制造商只需要用到三种光源：

red, green, and blue,

红、绿、蓝

which is lucky for them, really.

这对他们来说真是太幸运了！