High-motion is the characteristic of video or film footage displayed possessing a sufficiently high frame rate (or field rate) that moving images do not blur or strobe even when tracked closely by the eye. The most common forms of high motion are NTSC and PAL video (i.e., "normal television") at their native display rates. Movie film (at the standard 24 frame/s) does not portray high motion even when shown on television monitors. History In the early 20th century when 35mm movie film was developed, producers found that 18–24 frames per second was adequate for portraying motion in a movie theater environment. Flicker was still a problem at these rates, but projectors solved this by projecting each frame twice, thus creating a refresh rate of 36–48 Hz without using excessive amounts of film. However, when television was developed, there was no corresponding way to capture a video frame and project it twice. The solution to this was interlace, which had a side effect that 50 to 60 images per second were presented to the viewer. Television producers found that these higher image rates made certain shots possible that were unacceptable on film. Camera pans and text scrolls could be faster. Handheld camera work seemed less objectionable, and most importantly, sports action was much clearer — particularly when following a ball was critical. Definition of high motion There are no commonly used imaging systems that run at rates higher than 30 frame/s but lower than 48 Hz, so 48 Hz or higher is the de facto standard for high motion. The effects of high motion can be reduced or negated by converter lag when NTSC video is converted to PAL, or vice versa (a particular problem for coverage of international sporting events such as the Olympic Games or the FIFA World Cup, for example); however, more recent motion adaptive converters can minimize this. Showscan's research indicates that an average of 66.7 frames per second is the upper limit of what the human eye can perceive, and higher frame rates have no further effect, except in reducing flicker. (See refresh rate.) High motion and the "video look" Until the late 1990s, programs shot on video always possessed high motion, while programming shot on film never did. (The exceptions: Certain motion simulators and amusement park rides included film projected at 48–60 frames per second, and video recorded on kinescope film recorders lost its high