A patent was granted to Warner Bros. for eliminating scanner noise from the image while maintaining the film grain. Listed as inventors on the patent are Michael D. Smith, Michael Zink and Christopher Nolan.
Michael Zink writes over at LinkedIn, “When Chris Nolan was re-mastering seven of his films for the 2017 release of “The Christopher Nolan Collection” on 4K UltraHD Blu-ray in HDR for Warner Bros. Entertainment, he noticed some objectionable digital noise in certain scenes, including some actors’ faces. While many dismissed the artifacts as film grain, Chris knew it was something else and wanted to get to the bottom of this — not necessarily for his own films, but to ensure better quality results for all the films in the archives.”
The following is the intro to the original paper by Michael D. Smith & Michael Zink, published by SMPTE (2019):
While physical film prints are not widely used for motion picture distribution due to the industry’s successful transition to digital cinema distribution, negative film and interpositive (IP) film are still frequently used as a source for motion picture releases in High Dynamic Range (HDR) and Standard Dynamic Range (SDR) formats. Modern productions that use film as the acquisition format typically scan the film negative in a film scanner and then use modern digital production processes such as visual effects, editing and color grading like modern digital camera workflows. Remastering projects leverages the thousands of film negatives and IPs that are stored in Hollywood studios’ vaults to create new versions of older titles. IPs were created in traditional photochemical film workflows and are often available for use in remastering projects. — Film scanning is a critical step in both modern film production and remastering workflows as it converts the analog medium of film to a digital format. The film scanning process itself can introduce scanner noise into the digital image which has different characteristics than the more familiar film grain noise. Film grain noise is inherent in the physical film medium itself and its visibility and characteristics vary based on the film format and the type of film used. Filmmakers often consider the characteristics of film grain as a visual aesthetic that can be leveraged creatively to enhance the storytelling. Traditional photochemical film workflows that did not use film scanners also were impacted by film grain noise. — Scanning different types of film elements (e.g. negatives and IPs) in different film scanners with different scan settings can lead to different results. The visibility of these differences changes when the scan is used to create an SDR Home Master or SDR Cinema release versus an HDR Home Master due to the increased luminance and contrast often associated with the HDR format. This paper quantifies these differences and explains the visual impact of film grain versus scanner noise with an emphasis on HDR video. Additionally, this paper describes our recent experiments with test films and presents visual examples of scanner noise and film grain noise.
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