The first person to hold the official title of Inbetweener was Art Davis, a name that history has largely forgotten despite his foundational role in the industry. In the 1920s, Dick Huemer developed a systematic approach to animation that relied on a division of labor, separating the creative vision of the key animator from the repetitive labor of filling the gaps. This system transformed animation from a solitary craft into an assembly line, allowing studios to produce content with unprecedented efficiency. Before this innovation, every single frame of movement had to be drawn by a single artist, a process that was incredibly slow and limited the scope of what could be achieved. The introduction of the light table allowed artists to trace and refine drawings with precision, creating a workflow where a primary artist would draw the key frames to define the movement, and then pass the scene down to assistants who would add breakdowns and inbetweens. This hierarchy ensured that the final product was smooth and consistent, but it also created a specific class of worker whose contribution was essential yet often invisible to the audience.
The Math Of Motion
Animation on twos has been used for over 100 years, appearing in the 1908 film Fantasmagorie, which is widely considered the first fully animated movie. The human eye perceives movement through a phenomenon known as the flicker fusion threshold, allowing animators to get away with drawing only 12 frames per second instead of the 24 required for a perfect illusion of fluid motion. When the number of inbetweens is too few, such as four drawings per second, an animation may begin to lose the illusion of movement altogether, resulting in a choppy and disjointed visual experience. Most movements can be done with 12 drawings per second, a technique known as animating on twos, where the artist draws one out of every two frames. Only very fast movements require 24 drawings per second, which is referred to as animating on ones. This decision is often an artistic choice rather than a technical necessity, allowing directors to manipulate the perceived weight and speed of a character. Slow movements may be animated on threes or fours, and different components of a shot might be animated at different frame rates to achieve specific effects, such as a character moving on twos while the background shifts every frame to create a panning effect.The Digital Revolution
Nestor Burtnyk and Marceli Wein at the National Research Council of Canada received a Technical Achievement Academy Award in 1997 for their pioneering work in the development of software techniques for computer-assisted keyframing for character animation. Their work marked a shift from the physical light table to the digital canvas, where sophisticated animation software enables the animator to specify objects in an image and define how they should move and change during the tweening process. Some of the earliest software that utilizes automatic interpolation in the realm of digital animation includes Adobe Flash and Animo, developed by Cambridge Animation Systems in the late 90s, followed by Tweenmaker, which was released around 2006. The free software program Synfig specializes in automated tweening, offering a powerful alternative to proprietary tools. This transition allowed for the creation of complex movements that would have been impossible to draw by hand, as the software could automatically render transitional frames using interpolation of graphic parameters. The result was a new era of animation where the inbetweener became a digital architect, defining the physics of the transition rather than drawing every single line.