What are Ones, Twos, and Threes in Animation?

Does changing the number of frames help realism?

These are a bunch of numbers

 Lifewire / Johnny Chew

If you've watched some behind-the-scenes videos of animators or ever talked to one about animation, odds are you've come across the terms ones, twos, and threes.

Animation is the stringing-together of still drawings, puppets, computer-generated images, or any number of static content to create the illusion of movement. Each second of animation comprises some number of frames per second. That's where these ones, twos, and threes come in.

One, Twos, and Threes

Ones, twos, and threes refer to how long a single image holds on camera in relationship to frames per second. Ones mean every single frame is different, so at 24 frames per second you'll have 24 individual and unique drawings with that second.

Twos means that something holds for two frames, rather than one. So, if we were to animate one second at 24 frames per second on twos, it means every other frame will be different. So we'd have a total of 12 individual drawings within that second.

Threes means that we have a single drawing hold for 3 frames in a row. So, if we did a second of animation at 24 frames per second on threes, that means we'd have 8 individual drawings, all holding for 3 frames at a time.

Four, Fives, and Sixes

You could work in fours, fives, or even sixes if you'd like.The more an image holds in a row before changing to a different image, the more choppy the animation looks. Anything above fours starts to look a little choppier and less smooth. There's nothing wrong with that—in fact, Bill Plympton has made a very good career for himself working where single frames hold for longer. It simply comes down to taste.

Now, where you get the most out of this idea of holding still images for longer periods of time comes when you start to mix them up. Plympton works at a pretty constant rate, but changing things up both helps with your desired motion as well as saves you time.

For example, if we're showing a pitcher wind up to throw a ball, we can use ones, twos, and threes to help accentuate the change in speed. We can have him preparing his wind up when they're nodding and shaking their head at the catcher in threes—for example, he's at rest here and not moving all that much.

When he starts his windup, we can switch to twos. So as he's bringing his leg up and getting ready to throw we can have these frames in twos. So each individual drawing stays on screen for two frames in a row. When he finally goes to throw the ball we can switch to ones, to accentuate that this movement is the fastest part of the action, so each frame is different from the last.

How Changing the Numbers of Frames Creates the Illusion of Realistic Movement

Mixing content and changing the duration of frames is a great way to create the illusion of a realistic or even stylized movement. Faster frames imply faster movement, so we can plan each frame be different to show that there is more change in the position of whatever object we're moving. The slower something goes, the more we can use threes or fours to show that between each frame, the subject moves a lot less.

It helps to think of ones, twos, and threes similar to how you would think of a storyboard. For each second of animation at 24 frames per second, you'll need to fill in 24 blocks. Ones, twos, and threes just decide how many times you can copy and paste an image into those 24 blocks you're trying to fill up.