Stephen Worth of the ASIFA-Hollywood Animation Archive Project Blog tells us a little about Lotte Reiniger and what is probably the oldest surviving feature-length animated film, "Adventures of Prince Achmed":
"... In 1923, Reiniger and her husband and business partner, Carl Koch began work on an ambitious project... a feature length silhouette puppet film based on "The One Thousand and One Nights". She worked with animator Bertold Bartosch and background artist Walter Ruttman for three years on the film. The paper cutouts were jointed using wires and delicately arranged on top of a lightbox, where it was photographed frame by frame. Reiniger continued to animate her distinctive silhouette films up into the mid-1970s. She passed away in 1981. ...
Archive volunteer, Eric Graf was perusing a local library book sale when he spotted an amazing find... a portfolio of prints from Reiniger's landmark film. Published in Berlin in the year the film was released (1926), this group of images shows just how beautiful Reiniger's work was... and how unique."
Reiniger's Prince Achmed 1926