Frames Per Second (Temporary Article)

FPS? Frames Per Second? Ones, Twos, How Do You Do's?

You're all set. You position your puppet, look through the camera or at a monitor, and take the first frame of your epic... Congratulations! Ready to move the puppet aga---

"Wait! How MUCH do I need to move the puppet? How many frames do I take to create, say, one second's worth of passable animation?"

Here's a cut-to-the-chase answer with no definitions, followed by a more detailed explanation:

The answer depends on where and how you intend to show your completed movie.

30FPS: TV Video (America, Japan, a few other places; NTSC video standard), usually shooting on twos except for extra smoothness or fine movement.

25FPS: TV Video (Europe, Australia, lots of other places; PAL & SECAM video standard), shooting on ones or twos.

24FPS: Sound film projection, shooting on ones or twos.

18FPS: Silent film projection, shooting on ones or twos.

10FPS - 30FPS: Web Video. 15FPS is pretty standard these days (Whether 10FPS is "passable" is HIGHLY debatable.) ---

DETAILED EXPLANATION:

This explanation has two parts: the technical moviemaking part, and the animating part. We'll use the example of a guy walking across the screen for illustration, and we'll say that in one second he takes one (slow!) step.

First, we'll deal with...

THE TECHNICAL MOVIEMAKING PART: Frame Rate and FPS

Movies consist of still images sequenced together, then shown in rapid succession. Our brains interpret this succession of images as continuous movement. The rapidity with which the still images replace each other is called the FRAME RATE.

The frame rate is fixed for the system the movie will be shown on.

A typical motion picture film camera shoots 24 individual pictures every second, so it will take 24 individual pictures of our actor taking one step: The frame rate is 24 FRAMES PER SECOND, or 24FPS. Traditional film projectors then show that film at 24 frames per second, and we see the motion reproduced in a relatively lifelike manner: we see our guy taking one step in one second.

Video shown on television uses different frame rates. In the US, Japan, and a few other countries, video is usually shot and shown at about 30FPS (technically, it's 29.97FPS). So, for the same one step that our actor takes, there will be about 30 individual frames. In Europe, Australia, and other places, video is shot and shown at 25FPS: there will be 25 individual pictures for our actor's one step.

On the Web, there is no set standard. The frame rate is chosen for practical reasons: the higher the FPS, the larger the file, which means that it takes longer to download (or it's harder to stream). In typical Web video, the lowest frame rate that produces results acceptable to the producer is chosen. A typical rate for Web these days is 15FPS. For "showing" purposes, you choose this rate using the settings in your codec software when you output your movie into a single video file.

When you're making a movie, it's good to ask yourself: How and where am I going to show it? If you want your movie to be shown on a traditional film projector, you'll shoot it at 24FPS (regardless of whether you're shooting on film or digitially through a computer for later transfer to film). If you live in Australia and want your movie to work on local television sets, you'll choose 25FPS. If you live in the U.S., and want your movie to work on television, you'll choose 30FPS or, if your software allows it, 29.97. If you never intend to show your movie anywhere but on the Web and you don't require supersmooth playback, you can choose 15FPS.

When in doubt, choose a higher frame rate over a lower one. You can always reduce the frame rate later by dropping some frames out. If you shoot your video at 12FPS intending it to be shown on the Web, then realize it's so good you want to show it to your Grandma on her television, you can convert it, but it won't look as good as if you'd shot it for TV video in the first place. Frame rate conversions are done all the time (for example, whenever a film is shown on American television), and it's always better to start with higher quality.

OK, that's enough for the technical moviemaking part of the answer. The thing to remember is, you're best off choosing your frame rate before you begin shooting.

THE ANIMATING PART: Shooting on Ones, Twos, Etc.

As an animator, YOU have to individually take each of the pictures in your motion sequence. Let's say you're in Canada making a video to be shown on your Granny's television set. Canada uses NTSC video standard, which is about 30FPS.

Our walking guy is now your puppet. You want him to take one step in one second. You'll have to take 30 pictures of him just for one second of video. Does that mean you have to move the puppet 30 times for that one slow step? Well, it CAN mean that. And if you do that, you will be "shooting on ones." That means, one "click of the shutter" for every puppet position. Shooting on ones creates the smoothest animation.

You can also take two identical pictures for every puppet position: "shooting on twos." In this case, you'll move the puppet twice as far for each position to end up with (roughly) one second of video. Why twice as far? Because otherwise, your puppet will only have taken half a step after you've clicked the shutter the 30 times. Shooting on twos generally creates a jerkier animation than shooting on ones; however, it is still quite acceptable for most purposes (especially for 30FPS. Even shooting on twos at film's rate of 24FPS can look acceptable). For a rougher look, you can shoot on threes or even fours... The more frames you take for each puppet position, the fewer times you have to move the puppet, the greater distance you will move the puppet, and the jerkier the animation will look.

During shooting--even during a single shot--you can change from shooting on ones to shooting on twos, depending on the effect you want. Sometimes, for example, camera moves will be shot on ones while puppet motion is shot on twos in a single shot. HOWEVER, you DON'T change your FPS in mid-shot or even mid-movie. The FPS is fixed in the device you'll be using to show your movie.

Experience will teach you when to shoot on ones or twos.

Notice that by shooting on twos at 30FPS, you'll be taking shots of 15 different puppet positions. If you later want to stream your video on the Web, you won't lose animation by converting your video to 15FPS.

Finally, a brief word about timing your animation. Let's say you want your puppet to raise an arm slowly. You raise your own arm and time the action with a stopwatch. It takes four seconds. You're showing your movie on Australian TV, so you're shooting at 25FPS. Therefore, you'll need 100 images to fill up four seconds. You've decided to shoot on twos. So, you'll need to position the puppet 50 times to get that four seconds of video.

LAST WORD

Even though this seems like a long discussion, it's really very brief and leaves out lots of details, exceptions, etc. But we hope it's useful as a starting point.