Premiering in Berlin on May 3, 1925, Der absolute Film (The absolute film) was a program of nonnarrative, nonrepresentational films, the first public screening of its kind. A Sunday matinee in a 900-seat theater on the Kurfurstendamm, Berlin’s main shopping street, it sold out almost instantly and had to be repeated a week later. The program included Hans Richter’s Rhythm 21 and 23, Viking Eggeling’s Symphonie diagonale, and Walter Ruttmann’s Opus II, III, and IV. Instead of using the movie camera to capture the world around them, these artists created sequences of abstract forms that change over time, working by photographing one film frame at a time to create animations.
The term "absolute film" has come to encompass a genre of film devoted to experimenting with and revealing the elemental components of cinema: light, the film frame, and time. As Richter explained in 1926, “The absolute film signifies the foundation of cinematic art. . . . The absolute film opens your eyes for the first time to what the camera is, can be, and wants!”
from Inventing Abstraction, 1910–1925, December 23, 2012–April 15, 2013
Rhythmus 21 is Hans Richter's first film...Richter went on to make Rhythmus 23 (1923)...and Rhythmus 25 (1925). In this first of the series, originally known as Film ist Rhythmus, he experiments with square forms. These forms appear in very simple to very complex compositions—from the beginning shots where the squares occupy the entire screen, to compositions with squares with the frame. The effect is a subversion of the cinematic illusion of depth. Richter creates a precise rhythm with the movement of these shapes. "The simple square of the movie screen could easily be divided and 'orchestrated,'" wrote Richter in 1952. "These divisions or parts could then be orchestrated in time by accepting the rectangle of the 'movie canvas' as the form element. In other words, I did again with the screen what I had done years before with the canvas. In doing so I found a new sensation: rhythm—which is, I still think, the chief sensation of any expression of movement."
from Circulating Film Library Catalog, New York: The Museum of Modern Art, 1984, p. 166