A systematic collection of photographs, without scientific or taxonomical ends, but with the simple intention of revealing the enormous potential embodied in photographs not produced in an art context. This activity has led to two of his most extensive projects, Bilder von der Strasse (developed over a period of thirty years and including photographs gathered in public places from 1982 to 2012), and Archiv (a monumental tribute to photography, catalogued by species, from 1986 to 1999).