Short answers, pulled from the story.
The human eye can process only 10 to 12 images per second as distinct pictures, yet it perceives motion at rates far exceeding this limit. This biological constraint, known as the flicker fusion threshold, is the invisible foundation upon which all modern visual media rests. When a computer display flickers faster than 50 frames per second, the majority of observers perceive the light as stable and continuous.
From 1927 to 1930, as various studios updated their equipment, the rate of 24 frames per second became the universal standard for 35-millimeter sound film. The introduction of sound film in 1926 forced the industry to abandon the variable frame rates of the silent era, as the human ear is far more sensitive to changes in frequency than the eye is. The industry chose 24 frames per second as a compromise, a rate that satisfied the technical requirements of sound synchronization while remaining close to the existing silent film standards.
Early silent films operated at a chaotic range of frame rates, typically between 16 and 24 frames per second, dictated not by technology but by the physical strength of the person turning the camera crank. By the mid to late 1920s, the frame rate for silent film had stabilized into a range of 20 to 26 frames per second, bridging the gap between the chaotic early days and the precision of the sound era. Thomas Edison famously declared that 46 frames per second was the absolute minimum required for the eye to perceive motion without strain, setting a benchmark that would eventually drive the industry toward standardization.
The frame rates of analog television were not chosen for their visual quality but were dictated by the frequency of the electric grid powering the world. Most of the world adopted 50 frames per second to match the 50-hertz mains frequency, while Canada, the United States, Mexico, the Philippines, Japan, and South Korea adopted 60 frames per second to match their 60-hertz grids. The frequency of the electricity grid was extremely stable, making it logical to use for synchronization, ensuring that the television signal remained locked to the power source.
Sixty frames per second has for a long time been considered the minimum frame rate for smoothly animated game play, ensuring that fast-paced action remains clear and responsive. Video games designed for PAL markets, before the sixth generation of video game consoles, had lower frame rates by design due to the 50-hertz output, which noticeably made fast-paced games, such as racing or fighting games, run slower. Computer monitors marketed to competitive PC gamers can hit 360, 500 frames per second, or more, providing a level of smoothness that reduces motion blur and input latency.
Frame rate up-conversion is the process of increasing the temporal resolution of a video sequence by synthesizing one or more intermediate frames between two consecutive frames. Algorithms for frame rate up-conversion are widely used in applications, including visual quality enhancement, video compression, and slow-motion video generation. The process is essential for modern video standards that support 120, 240, or 300 frames per second, allowing frames to be evenly sampled for standard frame rates such as 24, 48, and 60 frames per second film or 25, 30, 50, or 60 frames per second video.