Peter Keetman's photography examines abstraction and structure — often through the use of wire screens and water nodules. That work established his reputation in Subjektive Fotografie and as a leading member of the postwar generation of German photographers.

In 1949 Keetman was a founding member of the avant-garde photography group foto form and played a decisive role in determining the direction the so-called subjective photography took. In the exhibition Subjective Photography put together by Otto Steinert in 1951 and in the accompanying photo book, Keetman's works have a formative role. From 1948, Keetman was represented with pictures in all major German and some international photo magazines. His work series Eine Woche in Volkswagenwerk (Volkswagen: A week at the Factory), which he photographed in 1953 in Wolfsburg, became particularly well known.