Persistence of Vision (POV) Guide.

Persistence of vision is a fundamental principle of animation. In fact, it’s the core reason why animation works in the first place - and the fascinating phenomenon that helps your art come to life. Read on to have persistence of vision explained, learn examples and get the full context on its workings - so you can learn how best to harness it with your creations.

What you’ll learn:

What is persistence of vision?

Persistence of vision is a type of optical illusion where the human eye continues to briefly see an image after it has disappeared from view. It is utilised in animation to give the impression of motion.

Also referred to as “retinal persistence”, physicist Peter Mark Roget first described the effect and offered a persistence of vision definition in the 19th century. He explained that the human retina can retain an image for a split second before another replaces it. This led to the discovery that having images replacing each other in quick succession gives the illusion of movement.

Everyday persistence of vision examples include:

  • The ‘continuous’ line of light you can see when a sparkler is waved around on bonfire night.
  • If an incense stick is moved quickly in a circular motion, a red circle of light is visible.
  • When looking at rotating blades on a fan, they appear to be continuous.

Persistence of vision in animation.

Creatives can use persistence of vision in animation to create engaging cartoons and films. By displaying several slightly displaced static images quickly one after another, we can 'trick' the observer into thinking that the pictures are moving.

This technique lies behind the core magic of all animation. It’s what allows the animation to appear smooth and seamless to the human eye - without being able to detect any joins between the static images.

How people perceive motion

Persistence of vision works as it does, because the human eye and brain are only equipped to process 10 to 12 images each second, whereas humans can retain an image for 1/15th of a second. This means that if another image were to succeed the first image within this space of time, it would appear continuous.

Frame rate

This refers to the number of still images or ‘frames’ that are used each second in an animation or film. In a piece of motion animation, there are two especially common ‘frame rates’: “On twos” or “On ones”. For these examples, imagine that you’re animating 24 frames every second.

  • "On twos" - animators generally shoot "on twos" when creating moving objects. This means that one image is displayed per two frames of film - so this example would result in 12 drawings every second.
  • "On ones" - is a more practical choice when creating objects that need to move very quickly. Each frame is unique, so that you will have 24 individual drawings each second.

It’s also possible to work “on threes”, “on fours” or even “on sixes” if it suits the animation style. The higher the number of frames the image holds in a row, the ‘choppier’ the animation appears.

Persistence of vision examples and techniques for animators

Now you know how fundamental persistence of vision is for creatives, let’s dive into the different techniques you can experiment with to enhance your use of this optical illusion.

Flipbooks

Flipbook animation offers simple examples of how persistence of vision can work in practice. The simple images in a quickly flicked notebook or pad move faster than the human eye can process, so rather than just seeing the individual drawings, it appears that the image is moving. This is a really fun technique to try out if you're starting with animation.

Animating on ones

Typically, 3D creatives animate “on ones”, as the motion of the character often needs to look smooth and polished - unless you’re trying to follow a particular style. You should animate on ones for scenes that need to be highly detailed or to best portray fast movement. Animating this way tends to be more expensive, however, so it’s no surprise you’re likely to find this being used in Disney films.

Animating on twos

Animating “on twos” is the most common animation form and can be used for simple movements. This is a great technique to work with for beginners and hobbyists looking to build confidence and experiment, but most films actually animate on twos as well.

Animating on threes

This style of animation is suitable for slow scenes, lower-budget productions or for the distinctive, highly detailed drawings and style that anime showcases. Cel shading is also used in anime to create a unique animation appearance.

You can use Adobe Animate to experiment with persistence of vision displays.

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The persistence of vision - history, innovation and inventions.

Get an understanding of the complete timeline of ‘POV’ and its use in animation, with our journey from past to present.

1. Discovery!

Peter Mark Roget, an English-Swiss physicist, formally identified persistence of vision in the 1800s. He referred to it as an eye defect, where objects in motion appear still at a certain speed.

Later inventions, including the phenakistoscope, showed that presenting individual images at a fast speed also creates the illusion of movement.

2. Scopes, tropes - and Victorian endeavour

Simultaneously invented in 1832 by Joseph Plateau in Brussels and Simon von Stampfer in Berlin (although the latter named the device a ‘Stroboscope’), the phenakistoscope became one of the earliest forms of animation and proven to be a popular Victorian parlour toy.

A phenakistoscope was a circular disc with individual drawings, which used the persistence of vision principle - as when the disc was spun, the drawings appeared to be moving.

The zoetrope, which followed the same principle but in a cylindrical shape, ultimately became even more popular and influential with Victorian audiences however. This rotating device boasts stripes with individual images, displayed inside a cylinder container with slits.

3. Disney embraces the phenomenon, to create a phenomenon

The same persistence of vision principles are evident in the earliest form of influential, hugely popular Disney animations. Working in the first half of the 20th century, the studio built upon earlier innovations to pioneer the traditional form of animation known as ‘cel animation’ - where characters are drawn on celluloid paper.

Animators sketched out each frame to create a sequence - much like a flipbook. Persistence of vision made the animation come to life and appear to be moving.

4. Modern era

Although creating animations has become far more digitalised, the fundamental core of all animation remains the same. When we watch our favourite animated film at home, it appears to flow seamlessly from one image to the next - even though TVs only show us a new frame every 1/24th of a second!

Roget would surely have been amazed at how ‘POV’ now enables millions of people to enjoy cartoons and anime through platforms like Netflix, each and every day.

Persistence of vision: FAQs.

How do you show persistence of vision?

Persistence of vision can be easily explained and shown through a simple flipbook. As you move through the static images quickly, you retain the previous image before replacing it with the next. This gives the illusion that the images are moving. You perceive the visual trace of the object for a split second after it has gone from your view, which helps to make the sequence seamless.

What is the difference between persistence of vision and phi phenomenon?

The phi phenomenon describes an optical illusion where stationary objects appear to be moving. The persistence of vision is the principle that allows this to happen - you retain the illusion of the first image even after it has disappeared - so the next image can seamlessly follow.

Creatives have fused the phi phenomenon and persistence of vision principle in practice, to create animations.

What devices are based on the persistence of vision?

Many of your household items are based on the persistence of vision principle - even your TV’s LED display! A persistence of vision display is propeller shaped and has blades of LED rotating constantly. The spinning motion helps to create the optical illusion and presents a seamless and continuous image.

Some digital advertisements also utilise the power of persistence of vision through holographic displays.

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