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  • [MUSIC PLAYING]

  • DAN COFFEY: All right.

  • Hello, and welcome back to another week of exploring digital media.

  • This week we're going to talk about the basics of video production.

  • We have wrapped up our still photography component which has been a lot of fun.

  • It's been really fun to see what you guys have done.

  • We're excited to see your projects.

  • And so now we move into the world of video,

  • where we're talking about more than just one frame at a time.

  • So speaking of which, as I said, we've been focused on one frame.

  • But now our camera is literally capturing at high speed

  • multiple frames at a time.

  • So there's a lot more that we have to think about as we do this.

  • So we refer to how many times we see an image per second

  • as the frame rate for a video.

  • And what is the frame rate of film?

  • Like, you go see a movie in the theater, what

  • is the typical frame rate you'll see?

  • Anybody know?

  • IAN SEXTON: A few answers from online.

  • DAN COFFEY: Yeah?

  • IAN SEXTON: We'll see 24 frames per second.

  • DAN COFFEY: 24 frames per second.

  • Yes.

  • Yes, exactly.

  • And certainly this graphic shows 60 FPS, 60 frames per second.

  • What IS 60 frames per second?

  • Why choose one versus the other?

  • That's kind of some of what we're going to unpack a little bit tonight.

  • But how about broadcast television?

  • How many frames per second is that shown at?

  • AUDIENCE: 24.

  • DAN COFFEY: 24.

  • No, actually, it's not.

  • So it goes back to some old standards, but 60 frames per second

  • is what broadcast television is sent at.

  • And that doesn't mean that the content that you're viewing

  • was recorded at 60 frames per second necessarily.

  • But it has been conformed to 60 frames per second as you watch it back.

  • All right.

  • So as far as frame rate goes, this all kind of comes down to human perception.

  • And how do we determine that 24 frames per second is the--

  • how did that become the standard for film making?

  • So let's look at a couple of clips here, starting

  • with just three frames per second, as you see on the top right corner.

  • Let's watch this and see how this little clip feels.

  • And to be clear, this is a video that was shot at a higher frame rate

  • and has been conformed to three frames per second.

  • But the effect is the same.

  • How did this motion feel?

  • Very unnatural, right?

  • Very kind of not pleasant to watch.

  • You're noticing every single frame rather than watching

  • the motion of the people walking.

  • So let's jump ahead here.

  • Here's six frames per second.

  • How does this one feel?

  • We're getting there.

  • We're kind of still seeing quite a bit of judder,

  • as we refer to as a frame rate that is very low and kind of clunky like that.

  • Let's move ahead to 12 frames per second.

  • OK.

  • Is that starting to feel a bit more like a natural motion?

  • Yeah?

  • And let's double up one more time.

  • Let's go to 24 frames per second, as we've already discussed

  • as the standard frame rate for film.

  • And so this kind of comes down to what it is that we're looking at.

  • We're looking at a group of pictures in a rapid succession.

  • That's all video is.

  • It's encoded a bit more smartly than that, but at the end of the day,

  • you're really just looking at pictures being--

  • it's like a flip book you open and flip through very quickly,

  • the images move forward.

  • So 24 frames per second has kind of become the standard.

  • Does anybody know the reasoning for why that was initially the standard back--

  • I don't even know the year that it was established.

  • But--

  • IAN SEXTON: I actually don't know off the top of my head either.

  • So I should look into it.

  • DAN COFFEY: So we'll look that one up.

  • But 12 frames per second is kind of where

  • we start to not be able to distinguish the difference between the still images

  • being flashed before us.

  • But 24 frames per second is the standard.

  • So my question is why.

  • No?

  • Go ahead, Alec.

  • AUDIENCE: I was just saying, to save money for 24 frames--

  • DAN COFFEY: Yeah.

  • Well, that's actually interesting.

  • That's a part of it.

  • So on this film strip here, we had 24 frames per second.

  • I'm sorry, where you have your film, you've

  • got your picture encoded alongside your audio.

  • So the audio track actually ran alongside the picture.

  • And one of the reasons--

  • film is not cheap, so we wanted to find a way to use as little as possible.

  • But we also needed to have enough fidelity in the audio

  • that it sounded nice and clear and sharp and was not too muddy

  • and that you could actually understand it.

  • And 24 frames was a good frame rate for that-- didn't cost too much,

  • you had a good natural motion to it, and you had good audio fidelity.

  • So that's kind of where the standard was set.

  • So the audio, as I said.

  • And so as we define our frame rate, we can kind of pick and choose this.

  • If you open up Shotcut or Adobe Premiere, or whatever

  • nonlinear editing system you're using, you

  • can say, hey, I want my project to be at this frame rate.

  • And so you can also additionally set your camera and say,

  • I want to shoot at 24 frames per second.

  • I want to shoot at 30 frames per second.

  • I want to shoot at 60 frames per second.

  • It kind of depends on the hardware that you're actually using.

  • But common frame rates that we might see--

  • 24 is equivalent to what we usually see for film.

  • A common video standard is actually 30 frames per second.

  • The soap opera effect where everything is very smooth,

  • that comes down to a 60 frames per second playback.

  • And then you've got some higher frame rates

  • at the other end that can be used for specialty things.

  • So you might have a camera where you're kind

  • of saying, hey, how do I actually set my frame rate in my camera?

  • And so if you've got a Canon, it might look like this.

  • If you've got a Nikon, like this, and a Sony, like this.

  • And the idea is that you're going to choose

  • your frame size, the actual width by height,

  • as well as how many frames per second.

  • And so looking here at top left with the Canon frame size,

  • we've got 1920, which is short for an HD frame, or 1920 by 1080

  • as the resolution, at 30 frames per second.

  • The "ALL-I" in this case just refers to how the frames are actually encoded

  • and means that it's easier for a non-linear editing system to actually

  • access every frame.

  • When you get these IPB frames, it's just a lighter weight

  • version of encoding where it's harder to decode is really what we need to know.

  • But it's much more space efficient.

  • So if you're given this option on a Canon camera, choose the ALL-I.

  • And so you can choose 30 frames per second, 24 frames per second,

  • or you can jump down to the next, the smaller resolution of HD video,

  • which is 1280 by 720, or 720p for short.

  • And so you can choose either of those as well.

  • You know, Nikon looks pretty much the same.

  • And with Sony, you actually need to choose your Kodak, what

  • the video is actually being stored as.

  • Kodak is simply that kind of container that holds all the frames together

  • and defines how it is actually encoded.

  • But we don't need to know those details.

  • We just need to know that you can actually choose on this camera.

  • And if you're using Sony, XAVC is just the newer video

  • codec that they are using.

  • So choose that.

  • And then you can choose what frame rate and frame size you want.

  • All right.

  • So overcranking and undercranking-- does anybody

  • know what these terms mean offhand?

  • We're talking about frame rates.

  • That's a little hint.

  • This "jif" here-- or GIF, however you want to say it-- is a hint as well.

  • Overcranking, what might this be?

  • Any guesses from online?

  • So what is this hand doing as it cranks?

  • What's happening?

  • What are we looking at?

  • We're looking at an antique camera.

  • But we're seeing two kind of things happen in the camera.

  • We're seeing this kind of wheel go around,

  • and we're seeing this bar here kind of slide up and down.

  • Any guesses?

  • AUDIENCE: Does it mean maybe that the [INAUDIBLE]

  • the succession of the images up and down?

  • DAN COFFEY: Yeah.

  • Benjamin is saying is this actually control

  • the speed, the images moving up and down.

  • So this is the shutter that we're seeing.

  • We're used to talking about shutter speed from still photography.

  • And then this is the--

  • I don't know what this is technically called,

  • but it advances the frames of film down through the camera as it moves.

  • And in the old school cameras, it literally

  • was a matter of kind of keeping a constant crank going

  • to determine your frame rate.

  • IAN SEXTON: It's called the claw.

  • DAN COFFEY: The what?

  • IAN SEXTON: The claw.

  • DAN COFFEY: The claw.

  • OK, yes.

  • So the claw hooks into the perforation on the film and pulls the frame down.

  • And so what happens if you start to crank this more quickly?

  • You overcrank.

  • The film advances faster.

  • And so what is the effect of that if you were to play it back?

  • AUDIENCE: Fast motion.

  • DAN COFFEY: Well, fast motion is what you would think.

  • You record a lot of frames very quickly.

  • But if you were to play them back at your normal frame

  • rate, the 24 frames per second, it's going to be slow motion.

  • So it's kind of counterintuitive in that sense.

  • But it's because you're cranking very quickly, recording a lot of data,

  • and then playing it back more slowly, you get slow motion.

  • So we thought to kind of show what this example

  • looked like, we'd set up in this beautiful Harvard Library and recruit

  • a boxer to kind of come in and show us what different frame rates can

  • look like.

  • So here we go.

  • We've got Conor Doyle here being a guest for us.

  • So yes, just a little hint as to what the setup looked like.

  • So the things we want to keep in mind here, I've kind of alluded to these,

  • are the captured frame rate-- this is the frame rate

  • that you set your camera to, how many frames per second you're

  • recording-- versus your project frame rate or your timeline frame rate--

  • how many frames per second are being played back over the sequence.

  • And they matter.

  • If they're the same thing--

  • so here, if you look at the top right of this frame,

  • we've got 24 frames per second being played back at 24 frames per second.

  • This is going to be a real time playback.

  • So as we watch this, Conor's punching the punching bag here.

  • All right, feels like normal time.

  • If you were standing there watching him, this is the speed at which it happened.

  • But if we look at--

  • we overcranked here, we cranked very quickly,

  • we recorded 250 frames per second.

  • And we play it back at 24 frames per second, roughly how--

  • what's the time delta here?

  • How many times slower is this going to be?

  • 10 times?

  • Yeah.

  • Because 24 times 10 is 240.

  • We'll round up to 250.

  • So 250 frames per second, his punching should be about 1/10

  • of the speed of normal time when we play it back.

  • And here it is.

  • So it really matters here, what is it that we want to do?

  • Do we want to slow things down?

  • We need to shoot at a higher frame rate.

  • But how much higher do we need to shoot?

  • And that depends on how fast your sequence

  • is, how many frames per second you're going to playback

  • that your viewer is going to watch.

  • All right.