The pictures are stills from a movie taken by one of the two movie camera's which were mounted on the thrust structure of the S-II stage on opposite sides. They were looking aft along the S-II thrust engines, towards the top of the S-IC stage. The countour of the interstage (10 meter in diameter) is made visible with a chain of bulb lights.
These camera's have only been used during the Apollo 4 and 6 missions to record and analyze the separation sequence.