What Digital Resolution is Needed to Scan Motion Picture Film: 4K, or Higher?

In the last few years, both digital intermediate (DI) postproduction systems and digital projection have advanced to full 4K resolution, avoiding the generation losses of traditional photo-chemical workflows. This leads to the question of how high a resolution is necessary to scan the film at the beginning of such a production chain. In fact, with the possibility that further improvements in both the DI and projection stages even beyond 4K could occur in future, it seems reasonable to conclude that the only limitation that should be applied at the scanning stage is the information-carrying capacity of the film itself.

This paper examines the questions of just what that limit is, what the required parameter values are – both analog and digital – to capture it, and what practical issues are involved in designing a film scanner that pursues such values.