Like live action, machinima is recorded in real-time, and real people can act and control the camera. Filmmakers are often encouraged to follow traditional cinematic conventions, such as avoiding wide fields of view, the overuse of slow motion, and errors in visual continuity. Unlike live action, machinima involves less expensive, digital special effects and sets, possibly with a science-fiction or historical theme. Explosions and stunts can be tried and repeated without monetary cost and risk of injury, and the host environment may allow unrealistic physical constraints. University of Cambridge experiments in 2002 and 2003 attempted to use machinima to re-create a scene from the 1942 live-action film "Casablanca". Machinima filming differed from traditional cinematography in that character expression was limited, but camera movements were more flexible and improvised. Nitsche compared this experiment to an unpredictable Dogme 95 production.