The photogram, image formation outside the camera is the real key to photography, it embodies the essence... that allows us to capture light on light sensitive material without the use of any camera.
Art of the 20th century, Part 1 by Karl Ruhrberg, Klaus Honnef, Manfred Schneckenburger, Ingo F. Walther, Christiane Fricke (2000) p. 627.