Take a series of still, sequential images.
Let’s look at them one by one.
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?
Intellectually, we know we’re just looking at a series of still images,
but when we see them change fast enough,
they produce the optical illusion of appearing as a single, persistent image
that’s gradually changing form and position.
This effect is the basis for all motion picture technology,
from our LED screens of today
to their 20th-century cathode ray forebearers,
from cinematic film projection to the novelty toy,
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.
This phenomenon of perceiving apparent motion in successive images
is due to a characteristic of human perception
historically referred to as “persistence of vision.”
The term is attributed to the English-Swiss physicist Peter Mark Roget,
who, in the early 19th century,
used it to describe a particular defect of the eye
that resulted in a moving object
appearing to be still when it reached a certain speed.
Not long after, the term was applied to describe the opposite,
the apparent motion of still images,
by Belgian physicist Joseph Plateau, inventor of the phenakistoscope.
He defined persistence of vision as the result of successive afterimages,
which were retained and then combined in the retina,
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
and up through the turn of the 20th century,
when some began to question what was physiologically going on.
In 1912, German psychologist Max Wertheimer
outlined the basic primary stages of apparent motion
using simple optical illusions.
These experiments led him to conclude
the phenomenon was due to processes which lie behind the retina.
In 1915, Hugo Münsterberg,
a German-American pioneer in applied psychology,
also suggested that the apparent motion of successive images
is not due to their being retained in the eye,
but is superadded by the action of the mind.
In the century to follow, experiments by physiologists
have pretty much confirmed their conclusions.
As it relates to the illusion of motion pictures,
persistence of vision has less to do with vision itself
than how it’s interpreted in the brain.
Research has shown that different aspects of what the eye sees,
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
via different pathways from the retina.
It’s the continuous interaction
of various computations in the visual cortex
that stitch those different aspects together
and culminate in the perception.
Our brains are constantly working,
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
in the moment-to-moment flow of the present.
So, in order to create the illusion of motion in successive images,
we need to get the timing of our intervals
close to the speed at which our brains process the present.
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
by measuring how fast the images need to be changing for the illusion to work.
Let’s see if we can figure it out by repeating our experiment.
Here’s the sequence presented at a rate of one frame per two seconds
with one second of black in between.
At this rate of change, with the blank space separating the images,
there’s no real motion perceptible.
As we lessen the duration of blank space,
a slight change in position becomes more apparent,
and you start to get an inkling of a sense of motion
between the disparate frames.
One frame per second.
Two frames per second.
Four frames per second.
Now we’re starting to get a feeling of motion,
but it’s really not very smooth.
We’re still aware of the fact that we’re looking at separate images.
Let’s speed up. Eight frames per second.
12 frames per second.
It looks like we’re about there.
At 24 frames per second, the motion looks even smoother.
This is standard full speed.
So, the point at which we lose awareness of the intervals
and begin to see apparent motion
seems to kick in at around eight to 12 frames per second.
This is in the neighborhood of what science has determined
to be the general threshold of our awareness
of seeing separate images.
Generally speaking, we being to lose that awareness
at intervals of around 100 milliseconds per image,
which is equal to a frame rate of around ten frames per second.
As the frame rate increases,
we lose awareness of the intervals completely
and are all the more convinced of the reality of the illusion.
Take a series of still, sequential images.