Persistence of Vision
This relates to how our eyes keep images for a fraction of a second longer than they appear, causing a sequence of fast flashes to emerge as one continuous image.
The persistence of vision is an optical illusion where visual perception continues after the object itself has ceased to exist. This effect occurs when people watch movies or television shows, giving them a much different experience than those who are illiterate and do not have access to written media.
Our eyes and brain can process only 12 separate images per second. Still, if an artist replaces an image during the time frame our vision retains it, we will create the illusion of continuity when viewing them.
How animators create persistence of vision
Animating on three’s
One of the things that complicate animating is the animation in “threes”. Threes means the animator has one drawing hold for 3 consecutive frames in a row. So if you wanted to do an 8-second animation at 24 fps on threes, then this would mean having some number of individual drawings all holding for three frames each between them.
Animating on two’s
For a realistic effect, animators adhere to the rule of “on twos”. This means that every second frame appears twice at 12 frames per second; this allows for smooth motion and makes things feel more naturalistic.
Animating on one’s
Animators can use “on ones” to show one image per frame of animation at 12 frames per second. This allows the action to go much faster than it could if the animator showed each individual drawing on its own time in-between pictures.
Where animators use persistence of vision
Generally, higher budgets like Disney films animate in one’s while most other films will use two’s as they tend to be lower budget, but the details often balance that out.
Anime typically uses third’s which is unique because it tends to have low-budget productions yet still contains high detail drawings for more engaging content with viewers regardless of their age or interest level.