Considered the oldest surviving animated feature film, The Adventures of Prince Achmed features a silhouette animation technique Reiniger invented which involved manipulated cutouts made from cardboard and thin sheets of lead under a camera. Reiniger required several years (1923 to 1926) to make the film as each frame (24 per second) had to be painstakingly filmed. No original German nitrate prints of the film are known to still exist. While the original film featured colour tinting, prints available just before the restoration had all been in black and white. Working from surviving nitrate prints, German and British archivists restored the film during 1998 and 1999, including reinstating the original tinted image. Die Abenteuer des Prinzen Achmed / The Adventures of Prince Achmed (1926) dir. Lotte Reiniger