Frame Rate and Animating On Ones vs On Twos

Frame rate is the frequency at which consecutive images (frames) are captured or displayed, measured in frames per second (fps). Human vision can distinguish only about 10–12 images per second as individual pictures; above that threshold the brain fuses them into continuous motion, which is why animation works at all. **The film standard.** Cinema standardized on **24 fps** between roughly 1927 and 1930 as a compromise rate when synchronized sound arrived. Television rates of 25, 30, 50, and 60 fps derive from electrical grid frequencies; North America commonly uses 59.94 fps. **On ones vs on twos.** A core animation decision is how many unique drawings or poses to make per second. Animating *on ones* gives a new image for every one of the 24 frames—24 unique poses per second—producing the smoothest motion, used for fast action. Animating *on twos* holds each image for two frames, giving 12 unique poses per second; it halves the labor while still reading as smooth, and is the workhorse default in traditional and stop motion animation. Budget television animation sometimes shoots *on threes* or *on fours*, yielding only 6–8 drawings per second. **Why it matters for cost.** The on-ones/on-twos choice directly sets how much work each second of footage requires. In hand-drawn and stop-motion production, every one of those 12 or 24 poses per second is a separate physical act—a drawing or a puppet re-pose—which is the root of the medium's labor intensity. See Why Stop Motion Is So Expensive: The Per-Shot Labor Bottleneck.