Color contrast | Color science | Computer Animation | Khan Academy · Khan Academy Labs
了解颜色对比的感知原理，学习如何通过调整对比度来增强视觉效果。适合练习颜色理论与视觉设计相关技能。
So far, we've been talking about color in terms of wavelength of light and human color receptors.
到目前为止，我们讨论颜色的时候主要是从光的波长以及人类对颜色的感知能力这两个角度出发的。
That's the physics part of color.
这就是颜色背后的物理原理。
Now let's turn to the perceptual part.
现在，让我们来看看感知方面的内容。
We just learned that every color has a hue, saturation, and lightness.
我们刚刚了解到，每种颜色都包含色调（hue）、饱和度（saturation）和明度（lightness）这三个属性。
But colors appear in our world alongside other colors, and that can really affect how they appear.
然而，颜色在我们的世界中总是与其他颜色共同存在的，而这确实会影响到它们本身的视觉呈现效果（即人们看到这些颜色的方式）。
It's also when things can get really, really weird.
也正是这个时候，事情会变得极其、极其奇怪。
For example, look at this image.
例如，看看这张图片。
Notice the two inner color rings.
请注意那两个内部的彩色环。
The one on the left looks green, the one on the right looks blue.
左边的那个看起来是绿色的，右边的那个看起来是蓝色的。
There are different colors, right?
有不同的颜色，对吧？
Nope.
不行。
If you take away the other colors, you'll see that they are in fact the same color.
如果你把其他颜色都去掉，就会发现它们实际上属于同一种颜色。
And it's not only color which can trick us.
其实，能欺骗我们的并不仅仅是颜色。
Different brightness levels will also affect how we perceive an image.
不同的亮度水平也会影响我们对图像的感知方式。
For example, look at the following gray scale image.
例如，请看下面的灰度图像。
Take a closer look at these two squares, A and B.
仔细观察这两个正方形，A和B。
One is a black square in the light.
其中一个是在光线中显现出的黑色方块。
The other is a light square in shadow.
另一个是一个被阴影笼罩的、颜色较浅的方形物体。
Do you think they are different shades of gray?
你觉得它们只是不同深浅的灰色而已吗？
Nope.
不行。
Let me show you.
让我来给你们演示一下。
They are in fact the same shade of gray.
实际上，它们属于同一种灰度。
So clearly not everything is what it seems.
显然，并非所有事情都像表面上看起来的那样。
How we perceive contrast or brightness depends very much on the surrounding image.
我们对对比度或亮度的感知在很大程度上取决于周围的图像。
And it brings us back to how the brain processes incoming image signals.
这让我们再次回到大脑如何处理传入的图像信号这个问题上来。
The structure of our visual system is optimized so that we can do important things, like survive.
我们视觉系统的结构经过优化，使我们能够完成一些重要的事情，比如生存下去。
But a key survival trait is the ability to very quickly identify danger.
但一个关键的生存能力就是能够迅速识别危险。
This requires the ability to rapidly refocus our attention when we need to.
这要求我们在需要时能够迅速重新调整自己的注意力方向。
Our brain does this by automatically refocusing our attention to dramatic changes in color, brightness or movement.
我们的大脑通过自动将注意力重新聚焦在颜色、亮度或运动方面的显著变化上来实现这一功能。
We call this difference in color or illumination, contrast.
我们将这种颜色或光照上的差异称为“对比度”。
Our brains are hardwired to notice when the colors contrast with each other.
我们的大脑天生就具备识别颜色对比度的能力（即当两种颜色相互形成鲜明对比时，我们能够立刻察觉到这一点）。
In the color mastering suite, we can adjust the contrast of an entire image using a contrast slider.
在色彩调色室中，我们可以使用对比度滑块来调整整张图片的对比度。
It works by increasing or decreasing the differences in brightness or the illumination levels across the image.
其工作原理是通过增加或减少图像中各区域的亮度差异或照明强度来实现效果的调整。
For example, notice the left half of this image has a lower contrast level than the right half.
例如，可以观察到这张图片的左半部分的对比度低于右半部分。
Getting this contrast level right is really important in Pixar movies.
在皮克斯的电影中，正确调整对比度水平至关重要。
For example, at the end of Inside Out in the headquarters, there's a scene where the character anger gets really,
例如，在电影《头脑特工队》（Inside Out）的结尾部分，当主角们回到总部时，有一个场景：主角们的愤怒情绪被彻底激发了出来……
really angry and to sort of heighten this sense of him flames exploding from his head.
他非常愤怒，这种愤怒的情绪似乎让他整个人都仿佛要“爆炸”一样（即情绪失控到极点）。
The surrounding area of the image is darkened so that the contrast difference is really quite extreme in that moment.
图像周围的区域被处理成了暗色，因此在这一瞬间，对比度差异显得非常明显（或者说极其强烈）。
These kinds of decisions are made by the director of photography.
这类决策由摄影指导负责做出。
And casually, we refer to them as the DPs.
我们随意地将它们称为“DPs”。