TED-Ed:运动的视错觉

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本短篇讲述了人的眼睛会在物体速度达到一定程度时出现幻觉的故事。


中英双语
Take a series of still, sequential images.
取一叠静止 连续的图像
Let’s look at them one by one.
我们逐一来看看
Faster.
加快速度
Now, let’s remove the gaps, go faster still.
现在 我们去掉停顿 继续加速
Wait for it … Bam! Motion!
等一下…… 砰! 动起来了!
Why is that?
那是怎么回事呢
Intellectually, we know we’re just looking at a series of still images,
从理性来说 我们知道自己在看一沓静止的图像
but when we see them change fast enough,
但图像更换的足够快时
they produce the optical illusion of appearing as a single, persistent image
它们会产生一种光学错觉 就像是只有一张固定的
that’s gradually changing form and position.
连续不断改变形状和位置的图像
This effect is the basis for all motion picture technology,
这种效果是所有电影技术的基础
from our LED screens of today
从如今的LED屏幕
to their 20th-century cathode ray forebearers,
到它20世纪老祖宗-阴极射线管
from cinematic film projection to the novelty toy,
从电影放映到新奇玩具
even, it’s been suggested, all the way back to the Stone Age
甚至 有人说 它可以一直追溯到
when humans began painting on cave walls.
人类开始在洞穴的墙上作画的石器时代
This phenomenon of perceiving apparent motion in successive images
这种在连续图像中感知视运动的现象
is due to a characteristic of human perception
是基于人类感知的特性
historically referred to as “persistence of vision.”
其在历史上被称作“视觉暂留现象”
The term is attributed to the English-Swiss physicist Peter Mark Roget,
这一术语出自英裔瑞士医生皮特•马克•罗杰克
who, in the early 19th century,
他在19世纪早期
used it to describe a particular defect of the eye
用这种说法来描述眼睛的特殊缺陷
that resulted in a moving object
即 运动物体达到一定速度时
appearing to be still when it reached a certain speed.
出现类似静止一般的状态
Not long after, the term was applied to describe the opposite,
不久之后 这个词被比利时物理学家
the apparent motion of still images,
转盘活动影相镜的发明者 约瑟夫•普拉托
by Belgian physicist Joseph Plateau, inventor of the phenakistoscope.
用来描述相反的物体 即静止图像的视运动
He defined persistence of vision as the result of successive afterimages,
他把幻象的持续性认定为连续余象的结果
which were retained and then combined in the retina,
幻象被存储 然后在视网膜中积聚
making us believe that what we were seeing is a single object in motion.
使我们相信 自己看到的 是独立的运动物体
This explanation was widely accepted in the decades to follow
这种解释在随后几十年得到广泛的认可
and up through the turn of the 20th century,
直到20世纪之交
when some began to question what was physiologically going on.
一些人开始质疑生理上发生的事情
In 1912, German psychologist Max Wertheimer
在1912年 德国心理学家马克斯•韦特海默
outlined the basic primary stages of apparent motion
用简单的视错觉
using simple optical illusions.
概述了视运动的初始阶段
These experiments led him to conclude
这些实验使他推断出
the phenomenon was due to processes which lie behind the retina.
这种现象是由视网膜背后的处理引起的
In 1915, Hugo Münsterberg,
1915年 雨果•闵斯特伯格
a German-American pioneer in applied psychology,
一位德裔美国应用心理学先驱
also suggested that the apparent motion of successive images
也提到了 连续图像的运动感
is not due to their being retained in the eye,
并非因它们被存储在眼中形成
but is superadded by the action of the mind.
而是被记忆行为附加上去的
In the century to follow, experiments by physiologists
在接下来的一个世纪 心理学家的实验
have pretty much confirmed their conclusions.
已经几乎证明了他们的结论
As it relates to the illusion of motion pictures,
图像动起来的幻觉
persistence of vision has less to do with vision itself
视觉暂留其实与视觉本身关系不大
than how it’s interpreted in the brain.
而与大脑对其解读有关
Research has shown that different aspects of what the eye sees,
研究显示 眼睛看到的不同形态
like form, color, depth, and motion,
比如形状 颜色 深度和移动
are transmitted to different areas of the visual cortex
在视网膜中 通过不同的神经
via different pathways from the retina.
传输到视觉皮质的不同区域
It’s the continuous interaction
这是视觉皮质中多重指令
of various computations in the visual cortex
持续的相互作用
that stitch those different aspects together
把各种不同的方方面面整合到一起
and culminate in the perception.
体会到了感官上的满足
Our brains are constantly working,
我们的大脑不断地运转
synchronizing what we see, hear, smell, and touch
把我们此时此刻看到的 听到的 闻到的
into meaningful experience
和触到的进行同步
in the moment-to-moment flow of the present.
以获得有意义的体验
So, in order to create the illusion of motion in successive images,
所以 为了在连续的图像中营造出运动的幻觉
we need to get the timing of our intervals
我们需要使停顿的时间间隔
close to the speed at which our brains process the present.
接近我们的大脑处理“此刻”的速度
So, how fast is the present happening according to our brains?
那么 对于我们的大脑 “此刻”发生的速度有多快呢
Well, we can get an idea
我们可以通过测量
by measuring how fast the images need to be changing for the illusion to work.
图像需要改变的速度来感知错觉
Let’s see if we can figure it out by repeating our experiment.
我们来看看是否能通过重复我们的实验看出来
Here’s the sequence presented at a rate of one frame per two seconds
这是按每两秒一帧的速度排好的图像
with one second of black in between.
在每两张之间有一秒的黑屏
At this rate of change, with the blank space separating the images,
更换过程中 用黑屏隔开两张图片
there’s no real motion perceptible.
不能察觉到明显的动作
As we lessen the duration of blank space,
当我们减少黑屏的时长
a slight change in position becomes more apparent,
位置上轻微的改变变得更明显了
and you start to get an inkling of a sense of motion
在分开的画面之间
between the disparate frames.
你开始有种动感的感觉
One frame per second.
每秒一帧
Two frames per second.
每秒两帧
Four frames per second.
每秒四帧
Now we’re starting to get a feeling of motion,
现在 我们开始有动起来的感觉了
but it’s really not very smooth.
但得确还不够流畅
We’re still aware of the fact that we’re looking at separate images.
我们还是能意识到 自己在看不同的图像
Let’s speed up. Eight frames per second.
我们加快速度 每秒八帧
12 frames per second.
每秒12帧
It looks like we’re about there.
看上去差不多了
At 24 frames per second, the motion looks even smoother.
在每秒24帧时 动作看起来更流畅了
This is standard full speed.
这是标准全速
So, the point at which we lose awareness of the intervals
所以 此刻我们就注意不到间隔了
and begin to see apparent motion
觉得是在运动了
seems to kick in at around eight to 12 frames per second.
看来在每秒8到12帧时开始奏效
This is in the neighborhood of what science has determined
这差不多正是科学断定的
to be the general threshold of our awareness
我们能区分独立画面的
of seeing separate images.
一般阙值
Generally speaking, we being to lose that awareness
总的来说 我们是在100毫秒每帧时
at intervals of around 100 milliseconds per image,
失去那种感觉的
which is equal to a frame rate of around ten frames per second.
也差不多等同于10帧每秒的帧频
As the frame rate increases,
随着帧频的增加
we lose awareness of the intervals completely
我们就完全没了间隔的感觉
and are all the more convinced of the reality of the illusion.
并且更加相信幻觉的真实性
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