Video feedback

David Sohn mentions video feedback in his 1970 book Film, the Creative Eye.

These filter types either mimic or directly utilize video feedback for its result effect and can be recognized by its vortex, phantasmagoric manipulation of the original recorded image.

Initially this was in black and white, and redone in 1967 to showcase the show's new 625-line broadcast resolution and feature the Doctor's face (Patrick Troughton at that time).

In the late 1990s it was found that so-called unstable-cavity lasers produce light beams whose cross-section present a fractal pattern.

Video feedback has been used to explain the essence of fractal structure of unstable-cavity laser beams.

Here the feedback is usually an undesirable phenomenon, where the light generated by the phosphor screen "feeds back" to the photocathode, causing the tube to oscillate, and ruining the image.

Optical feedback has been used experimentally in these tubes to amplify an image, in the manner of the cavity laser, but this technique has had limited use.

Douglas Hofstadter discusses video feedback in his book I Am a Strange Loop about the human mind and consciousness.