quotes from Expanded Cinema, written by Gene Youngblood (1970)

"Keying and Chroma-Keying

[...]

While demonstrating the nature of Chroma-Key, these examples also clearly show how a purely electronic medium with an unexplored range of possibilities has been used to imitate the older discipline of cinema, and to express an archaic intelligence that insists upon "objectivity" and linear development in graphic forms. The rigid adherence to "clean" matting implies disdain toward what is obviously the unique property of video keying: "metamorphosis," not overlay or insertion. The new consciousness seeks the transforma- tion of realities whereas the old consciousness ventures no further than a timid juxtaposition of "objective" realities that retain their trad-i tional identity. The fact is that there exists no cinematic equivalent of video keying. Tearing a key in grays or colors produces graphic designs of unique character, blending form and color in a manner virtually impossible in any other medium. Video keying is inherently synaesthetic; such a claim can be made for no other aesthetic medium." (p. 273)

"Feedback

If a microphone is placed too close to its amplifier it squeals. If a television camera is positioned too close to its monitor it squeals also, but it squeals visually. This visual noise, like audio noise, is called "feedback." Video feedback may be intentionally induced and carefully controlled to produce graphic effects possible only through this technique. The most common effect is the infinitely-repeated image similar to the infinity effect of fun house mirror chambers. This can be done with one, two, or three cameras shooting into the same monitor that displays their output. One or two cameras can shoot into a monitor that displays their output in addition to an image from a third camera. There are a number of combinations based on the principle of the squealing camera." (p. 274)