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像素工程:长时间曝光摄影 – 译学馆
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像素工程:长时间曝光摄影

Pixel Engineering: Long Exposure Photography

大家好,我是Jeff
Hey there, I’m Jeff.
我是Steve
And I’m Steve.
我们是麻省理工学院的学生
And we’re students at MIT.
今天,我们要给你们展示一些很酷的东西
Today we’re going to be showing you
只要用一些摄影和科学的知识
some really cool things you can do with photography and science
在家里就可以做
at home.
像这样的东西
Things like this.
[音乐播放]
[MUSIC PLAYING]
相机固定得很稳定
It stays still.
这样就非常好
So it’s pretty cool like that.
你也可以这样使用
You can let it go like that.
(音乐播放)
[MUSIC PLAYING]
我们在麻省理工学院博物馆看艾哲顿博士的展览
We’re here at the MIT Museum at the Doc Edgerton exhibit.
艾哲顿博士是麻省理工学院的专家
Edgerton was a professor at MIT who
他率先使用频闪摄影
pioneered the use of the stroboscope in photography
拍摄了像这样美轮美奂的东西
to capture images like these.
频闪灯能像连发手枪一样频繁精确地闪光
The strobe can be precisely triggered
在瞬间之内照亮拍摄对象
to illuminate the subject for only an instant,
能让相机在一瞬间记录动体的连续运动过程
allowing the camera to capture a moment frozen in time.
今天,我们要做的不是捕捉瞬间
Today, instead of capturing an instant,
而是要做长曝光摄影
we’re going to be doing long exposure
来拍摄一段时间内发生的事物
photography to capture events as they take place over time.
让我们回到实验室
Let’s go back to the lab and meet up
跟Steve研究科学
with Steve for some science.
模拟激光噪音
[MIMICS LASER NOISES]
Jeff,你的实验外套在哪里
Jeff, where’s your lab coat?
哦,不好意思
Oh yeah, sorry.
(两人模仿激光噪音)
[BOTH MIMIC LASER NOISES]
现在我们换上实验服啦
Now there we’re in properly lab attire,
让我们来看看基本的相机设置
let’s look at our basic camera setup.
这儿是光源
Here’s our light source.
这是我们的场景,在镜头的焦距之上
This is our scene, which is at the focal distance of our lens.
这是光圈,快门
He’s our aperture, our shutter, and our piece
以及一卷胶片,也可以说是数字传感器
of film or digital sensor.
现在,让我们在这种条件下,仔细看看这个传感器
Now let’s take a closer look at, in this case, or sensor.
当光线透过来的时候
We can think of each of these squares
我们可以把每个小方格
as representing a pixel which cumulatively records light
看做是一个可以累积记录光的像素
as it hits it.
现在,如果我们打开光圈
Now, if we open up the aperture, we
就可以看到图像呈现在传感器上
can see the image resolve on the sensor.
通过不断改变光圈大小
By changing the size of the aperture,
就可以控制传感器上的进光量
we control the amount of light that hits the sensor.
另外一种控制进光量的方法就是用快门来控制
Another way of controlling light is the shutter.
由于传感器的累积特性
Because of the cumulative nature of the sensor,
打开快门的时间长
opening the shutter for a longer period of time
就意味着每个像素点可以记录更多的光
means each pixel records a higher light count,
得到的图像就会更亮
resulting in a brighter image.
这是长曝光摄影的关键所在
This is the key to long exposure photography.
现在,要理解这一点的另外一个方法,就是来看个例子
Now another way to understand it is to look at an example.
现在,我在一个小黑屋里挥动着手电筒
Here I am in a dark room waving a flashlight around.
实际上,你看到的视频
The video you actually see is made up
都是由一些连续拍摄的照片组合到一起
of successive photographs, or frames, played back to back
大概以每秒24帧的速率播放
at around 24 frames per second.
如果我们把所有的照片叠加到一起
If we superimpose all of these photographs together,
我们就一个大概看起来很像这个场景的
we get a discrete approximation to what a long exposure
长曝光图像
this scene would have looked like.
这是因为相机的累积性
This is due to the cumulative nature of the camera.
下面才是这种图像的
Here’s what the actual continuous long exposure
真正的连续长曝光
of the scene looks like.
既然我们已经了解了基本原理
Now that we’re past the basics, let’s talk about how
那让我们来看看你在家里可以怎么做
you can do this at home.
首先,你得有一个黑暗的环境,一台相机
First you’ll need a dark environment, a camera,
一个三脚架,或者是一个能固定住相机的地方,一个光源
a tripod, or a steady place for the camera, a light source,
当然,要是能有一位可爱的助理会更好咯
and it helps to have a happy assistant.
第二点,你需要设置一个较慢的快门速度
Secondly, you need to set your camera to a very slow shutter
通常来说,至少五秒或者五秒以上
speed, typically at least five seconds or more.
如果你有一台单反相机
If you have a digital SLR, this is
那么使用手动模式或者B门模式就会很简单了
easy to do using manual or Bulb mode.
如果你有一台小型照相机
And if you have a compact camera,
就可以把相机设为烟火模式或者夜景模式
you can set the camera to fireworks or night mode
让相机进行长曝光拍摄
to trick the camera into taking a long exposure.
接下来,按下快门,同时,让你的助手
Next trigger the shutter, and have you or your assistant wave
在相机面前挥动光源,写一些字或者画一些形状出来
a light in front of the camera to write words or draw shapes.
当快门关闭后,你就可以得到一幅光绘作品了
After the shutter closes, you’ll have your light painting.
长曝光摄影有很多用途
There are many uses for long exposure photography,
不管是用于科学还是艺术
both scientific and artistic.
例如,你可以测量一个物体的速度
For example, you can measure the speed of an object
比如汽车或者飞机
like a car or a plane.
这儿是一条飞机划过的痕迹
Here we have a plane landing.
如果我们知道距离和快门速度
And, if we know the distances, and the amount of time
我们就能够
the shutter was open, we can actually
计算出飞机的速度
calculate the speed of the plane.
如果你有一个在黑暗中可以发光的弹跳球
You can also see the parabolic trajectory of an object if you
那你就可以看到弹跳球的抛物线轨道
have a glow-in-the-dark bouncy ball.
根据长曝光的时间,就可以计算出弹跳球的减速过程
From the long exposure, you can calculate the decay of bounces
并且你也可以看到
as well as notice that the path of the ball
弧形轨道的顶端会亮一些
is brighter at the top of the arcs,
因为弹跳球在靠近弧形顶端的时候速度会变慢
because it is moving more slowly near the apex.
长曝光的另一个应用就是天体摄影术
Another cool application is astrophotography.
如果你把星星作为光源来拍摄
If you use to stars as your light source,
那你就可以看到地球的旋转
you can see the rotation of the earth.
在旋转中心
And, if you trace back to the center rotation,
你可以看到北极星
you’ll find the North Star.
最后,如果你也在麻省理工学院,
Finally, if you’re at MIT, and just happen
而且刚好有办法弄到一个高科技的机械臂
to have access to a high-tech robotic arm,
你就可以做一个超级精确的光绘作品了
you can do super precise light painting.
让我们来看看吧
Let’s check it out.
现在,我们和介导物质组在麻省理工学院媒体实验室
We’re here with the Mediated Matter group at MIT Media Lab,
我们要用这个机械臂创造一幅光绘作品
and we’re using this arm to do light painting.
在机械臂上尾部安装上一个光源
By attaching a light to the end of the robotic arm,
就可以创造出一幅这样的光绘作品了
we can actually create light paintings like this.
因为机械表能进行精确的操控
Because of the precise control of the arm,
所以我们就可以制作一个视频
we can actually make animations where every successive video frame
视频的每一帧都是拍摄的光绘图片
is its own light painting.
我们也可以通过附加一个传感器对隐藏区域可视化
We can also visualize hidden fields by attaching a sensor
通过传感器来控制光的亮度
and controlling the brightness of the light with the sensor.
例如,这是我的笔记本电脑,你可以看到
For instance, this is my laptop, and you see the magnetic field
电脑周围的磁场
surrounding it.
哇哦,这机械臂真是相当酷啊!
Wow, that arm was pretty cool.
那是必须的!但是记住,
Definitely, but remember, you don’t
你不需要用一个机械臂,你只要一个电筒和相机
need a robotic arm, just a flashlight and a camera
就可以尝试光绘摄影了
to try out light painting.
好的,这次视频到这儿就结束了
Yeah, well that’s the end of our video.
我们希望你会喜欢
We hope you enjoyed it.
这是我们第一次尝试着做这个内容
And this was our first try doing this,
如果你有任何评论,建议
so if you have any comments, suggestions,
或者你只是想和我们分享一些照片
or even if you just want to share some photos with us,
可以通过这个方式随时联系我们
feel free to contact us at this right here.
这个方式就可以联系上的
This will work.
谢谢观看
Thanks for watching.
(音乐播放)
[MUSIC PLAYING]

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视频来源

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