How does cel animation work?

Tony explains how cel animation works and emphasises that, although much of the production process now takes place on computers, most of the principles remain unchanged.

Working at first on paper, a traditional cel animation team will plan out and sketch the animated frames (roughs) or the key positions in a sequence before sketching in every frame of the sequence (inbetweening). Each drawing is then inked and coloured onto transparent sheets or cels – from which the technique gets its name. The transparencies are then photographed, in sequence, on top of a painted background.

Sometimes numerous sheets are layered on top of each other as more than one character or object is moving. To give perspective, multiple cels can be arranged on separate planes in a technique called multi-plane animation. You can see how multi plane camera was developed by the Disney studio in this short extract.

Animators working in 2D still use all of these techniques now, though they can be simulated for ease and speed in a computer program. However, many animators will at least start the process on paper, either for development or to create a particular ‘look’.

Is there anything that surprises you about the cel animation process?