Party no 9 (1967)
Karl Bayer was a stills photographer for many movies. Looking at his
IMDb filmography it may appear that his career ended in 1970, but that is misleading. Instead, he acted as stills photographer for many German sex films during the 1970s, but these films kept the credits lists always very short. However, Mr Bayer usually made cameo appearances in the films he photographed for (as the article mentions), and I spotted him so far in 9 of those films, in particular several of the Schoolgirl-Report series.