The traditional explanation of moving pictures: an image lingers on the retina for a fraction of a second, so successive frames blend into continuous motion.
The idea of an afterimage lingering in the eye is ancient, and an 1824 paper by Peter Mark Roget on the appearance of moving wheels is often cited as its modern source. It became the stock account of how film works in textbooks and encyclopaedias for most of the twentieth century. In 1978 and 1993 Joseph and Barbara Anderson argued that it was a myth: a lingering image would produce a blur of superimposed frames, not motion.
In practice
- A film studies lecture opens by explaining that the eye retains each frame until the next arrives.
- A museum display of zoetropes credits the illusion to the retina holding images.
- Possible explanations
- The appeal of the account is that it is simple and true in part: visual responses do last briefly, which is why flicker vanishes above a certain frame rate. What it does not explain is why the frames are seen as movement rather than as a stack of overlapping pictures.
- In its favour
- Defenders note that the persistence of visual responses is real and does explain why a projector's flicker becomes invisible, so the term retains a legitimate meaning when confined to that.
- Against it
- Perception researchers and film scholars, following the Andersons, generally reject it as an explanation of motion, attributing apparent movement instead to the brain's motion processing, as in the Phi Phenomenon and beta movement.
- Standing
- A case of an explanation surviving in teaching long after specialists abandoned it. Compare the Phi Phenomenon.
- Further reading
- Wikipedia
- Subject
- Communication & Media
- Essay
- Theories of what stands between an event and its audience