Ruttmann's "Opus 1", which premiered in 1921, is the first abstract or 'absolute' work in film history. It contains no images of reality, but consists only of colours and forms, as Ruttmann had already formulated in his manifesto for a "painting with time". In 1919, he wrote that it took him almost ten years to "master the technical difficulties" that stood in the way of his idea, formulated as early as 1913, that one should be able to "work with film as with brush and paint".