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相机上的“卷帘快门效应”有什么用? – 译学馆
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相机上的“卷帘快门效应”有什么用?

Why Do Cameras Do This? (Rolling Shutter Explained) - Smarter Every Day 172

大家好吗?我是Destin
What’s up? I’m Destin.
这里是《每天聪明一点》节目 现在拿出你的手机
This is smarter every day get your phone now.
你看到这个小摄像头附件了吗?
You see that little camera assembly there.
我们把它从手机上取下来
Let’s take it out of the phone.
是的 它长这样
Yep, that’s what it looks like.
我们要这么做
So here’s what we’re going to do.
首先我们要把透镜移除
The first thing we’re going to do is pop the lens off,
大家看 这个叫做CMOS传感器
and there we go, that is called a CMOS sensor
这就是你手机的摄像头
that is the camera on yourphone.
互补金属氧化物半导体
Complementary metal-oxide-semiconductor.
那么当你用手机拍照或录像的时候
So when you take a photo or a video with your phone,
你以为感光元件是一下子整体曝光的
you will think that it exposed that entire chip at one time
就像相机快门那样
like snapping a photo.
其实它的原理并不是这样
That’s not heavy works.
实际上光线是以扫描的形式成像的
It actually scans down the chip and
这就是数码成像的原理
that’s how images are created.
我们称为“卷帘快门效应”
This is called rolling shutter
这也就是为什么你的手机
and it’s the exact reason your cell phone
拍摄快速运动物体时会产生怪异形变
makes wired shapes out of fast-moving objects.
这是一部平板扫描仪
This is a flatbed scanner and
我拿着一个圆形标签
I have a circular patch right here.
如果我把标签面朝下放在扫描仪上
If I were to take this patch and set it face down on the scanner,
然后在扫描时随着扫描元件移动方向
and I were to start the scanner and move the patch
同时慢慢移动这个标签
in the same direction as that moving row of pixels,
看看扫描结果 你可能想到了 它会是圆形的吗?
check out what happens, you are smart, is this going to look like a circle?
不 不是圆形的 而是被拉伸了
No, it’s not a circle, it stretched out.
这是有道理的对吧?
And that makes sense right? You’re stretching
图像被拉伸是因为你跟着扫描元件移动标签
that image because you’re moving it along with the scanner.
那么相反 如果我反向移动
Now, conversely what’s going to happen if
迎着扫描元件移动会发生什么
instead of moving it with the scanning row pixels we move opposite.
这次不会拉伸 那会怎么样呢
It’s not going to stretch it out is it what’s it going to do,
这次会把圆形压扁
It’s going to compress that circle down
你手机摄像头的卷帘快门效应和这个很像
a rolling shutter on your cell phone camera is very much like this
只不过它是从图像上方开始
is that it goes from the top of the image all the way.
一直扫描到底部
All the way down to the bottom that means that
这意味着你看到的并不是真相
what you’re seeing is actually a lie,
而像是不同时间图像的一个堆叠
it’s like a stack up of several different moments.
好的 现在我们知道了它的工作原理
Okay now that we understand how this works,
下面就是见证奇迹的时刻了
it’s time to visualize in the most turbo awesome way possible.
过去的三年中 只要我手头
Over the past three years, anytime I had
同时有手机和一部高速摄像机
a phone and a high-speed camera at the same place at the same time.
我就会拍一些卷帘快门的特效照片
I would be able to look out for rolling shutter events,
并且用手机录下来
and I would video with the phone,
然后使用高速摄像机拍下来
and then I would video with a high-speed camera,
这样我就能通过手动回放模拟卷帘快门
so that I could go back and manually simulate rolling shutter
来理解这种效应是如何产生的
to let you understand exactly how the artifacts were created.
这实在是非常酷
This is so stinkin cool.
你一看到就会明白
Your brains going to get it instantly
我们先用iPhone拍一段视频
we’ll start with iPhone video
然后我们来看模拟结果 非常酷
and then we’ll go to the simulation “piu” result.
这是我第一次意识到我可以人造卷帘快门效果
This is the first moment I realized I can fake rolling shutter.
我坐在一架螺旋桨飞机里穿越澳大利亚内陆
I was in a terrible problem over the Australian outback
我意识到当我旋转手机时这个图案会随之改变
and I realized that the patterns would change as I rotated my phone.
我手头碰巧有高速摄像机
I haven’t have a high-speed camera with me so I’ve gotten down
所以我就开始拍摄 采集数据
and I started collecting data.
这就是你的摄像头每秒都要重复多次的事情
This is what your camera does dozens of times per second.
我注意到图案会有不同的变化
I noticed that the patterns are very different depending on which way
这取决于螺旋桨相对于快门的旋转方向
the propeller rotating relative to the rolling shutter.
这真的很美 但是很遗憾
This is really beautiful, but I was kind of bummed that
我没法从螺旋桨的头部拍摄
I didn’t get to see the effect head on to the propeller.
多年之后 当我上高空飞行课时
Couple of years later though, when I was taking high altitude flight lessons
在科罗拉多的派克斯峰附近
near Pikes Peak in Colorado.
我终于有机会在跑道上从螺旋桨正前方拍摄了
I finally got my chance the video a propeller head-on on the tarmac.
指尖陀螺已经流行了一段时间了
The fidget spinner community has known for a while now
在户外明亮光线下用手机拍摄陀螺时
that when it’s really bright outside a cell phone camera videoing a fidget,
陀螺旋转的样子就是人们所谓的“怪异形状”
spinner will turn it into what they call the thing.
其实这只是略微带点混叠的”卷帘快门效应”
It’s just rolling shutter with a little bit of aliasing thrown in,
让它看起来像是某种忍者飞镖
but it looks like some kind of ninja alien throwing star.
而当你通过高速摄像机拍摄慢动作时
Anyway, when you slow it down with a high-speed camera,
你就会发现它的形状变得非常奇怪
you can really reveal the map that makes this look so weird.
我一个哥们会弹吉他和曼托林
My buddy been plays both the mandolin and the guitar,
为了拍出弹奏时的“卷帘快门效应”
and it took us a really long time to get the rolling
我们费了很多功夫
shutter effect to show itself.
但拍出来以后 画面真的很棒
But when we did, it was awesome.
– 哦 太牛了- 哦……快看啦
oh-hoooo, oh win, oh work will, oh.[ guitar music]
[笑声]
[ laughing][ guitar music]
因为吉他弦震动频率太高 所以拍摄极难
Guitar strings are especially difficult because they vibrate so quickly
普通的高速摄像机根本不够快
that a normal high speed camera isn’t fast enough.
我们需要以每秒钟20000或28000帧的频率拍摄
We had to record them at 20,000 or 28,000 frames per second
才能够得到较好的模拟效果
to be able to run this simulation properly.
最后一个好玩的现象我以前没有见过
The last trick is something I had never seen before,
是别人告诉我的
but somebody told me about.
如果你拍摄一个旋转的硬币
If you video a coin spinning,
你能在硬币的边缘看到一个螺旋形状
you can see a swirl pattern on the edge of the coin.
是的 这也是“卷帘快门效应”
Yep, that’s also rolling shutter.
显然制作这个需要相当长的时间
Obviously this took a really long time to make
来自《分钟物理》的Henry功不可没
and Henry from minutephysics made it possible.
就是他发明了利用AE
He’s the guy that figured out exactly
来模拟“卷帘快门效应”的
how to make After Effects simulate rolling shutter.
画中画里是幕后花絮视频
All the behind the scenes video on the second channel Henry
其中Henry和我在商量怎么做视频
and I talked about what we’re trying to accomplish.
我们会给Henry宣传一下 你可以去看看
Go check it out and moan will throw some love Henry’s way.
我们还要感谢我们的赞助商Audible
Also, once they thanks to the sponsor which is audible
在介绍我在Audible上听的一本有声书之前
before we talk about the book that I’m listening to an audible right now.
让我们和小鸡们玩玩“卷帘快门效应”游戏
Let’s go goof around with rolling shutter and some chickens.
我正在听的有声书叫做
Okay, the book I’m currently listening to on audible
《白色城市的恶魔》
is called the devil in the white city.
这是本很棒的书 讲了1893年的芝加哥世博会
it’s a really good book about the 1893 Chicago World’s fair,
这次世博对美国造成的影响之大 让人不敢相信
a fair that I had no idea changed America, but it did.
还讲了美国第一个连环杀手 就是这个
Also America’s first serial killer, so there’s that.
很疯狂 我也不敢相信
It’s pretty crazy, I had no idea.
很不错的故事 你应该看看
It’s a great story you should check it out.
Eric Larson写的《白色城市的恶魔》
Devil in the White City by Eric Larson.
你会喜欢的
If you will enjoy it,
你可以登陆audible.com/smarter获取
you can get that by going to audible.com/smarter.
这事有两方面好处 首先你免费得到一本有声书
That is two things number one you get a free audiobook,
其次我也受益于背后的网络点击量
and number two I get secret internet points,
因为若Audible知道您从《每天聪明一点》登陆
because audible knows you came from smarter every day
以后就会给《每天聪明一点》更多支持
and they’re more likely to support smarter every day in the future
这对我及我的家人都非常重要
and that’s a big deal for me in the family.
非常感谢
I appreciate that.
总之如果你看到有人谈论“卷帘快门”
Anyway, if you see anybody that talks about rolling shutter,
告诉他们原理 别和混叠即“车轮效应”搞混了
make sure they don’t get confused with aliasing, that’s the wagon wheel effect
很多人都会将两者混为一谈
a lot of people get those too confused.
我希望这个视频对你有所帮助
I hope this video earned your subscription,
如果没有 也别介意
if it didn’t, no big deal.
我是Destin 每天聪明一点
I’m Destin, you’re getting smarter every day.
祝您天天快乐 再见
Have a good one, bye.
最后一只鸡
Last chicken, bright chicken.
非常勇敢

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视频概述

卷帘快门最早出现在单反相机上,我们现在的手机摄像头仍然使用了这种快门。视频中将介绍一种有趣的“卷帘快门效应”

听录译者

收集自网络

翻译译者

AF

审核员

审核员JF

视频来源

https://www.youtube.com/watch?v=dNVtMmLlnoE

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