Motion Picture Colour Science and film ‘Look’: the maths behind ACES 1.0 and colour grading

One of the biggest colour-related problems for the film production and post-production industry is two-fold: to ensure that the creative“look” of video content, as envisioned by the cinematographer, is preserved throughout ([1]– [2]), and to be able to consistently reproduce this ([1], [3]). That also has to be independent both on digital cameras or computers generating and animating it (as input), and on finished asset specifications for the end-users to watch and enjoy it (as output) — be it either in a dark digital cinema theatre, at a home TV setting, or using a Video-on-Demand (VoD) or Internet- streaming application, in a day-lit room or even open sunlight. In recent years many proprietary/commercial tools and workflows emerged, each driven by specific, not always cross-compatible needs (e.g. on-set grading, Digital Cinema mastering, VoD, etc.). This results in proliferation of a plethora of different formats vs. the scarce number of really interoperable standards. After a minimal introduction to colour-mathematical terminology ([4]–[6]) and ColorLUTs, two brand new colour-management techniques from high-profile moving-picture digital imaging (CDLs and ACES) will be described, as they aim at colour interoperability for the analysis and synthesis of digital ‘looks’, both on-set (production) and along the Digital Intermediate (DI) phase. ACES in particular, which the author has been active contributor to since 2012, is an Academy-originated initiative for facilitating colour interoperability across the Media & Entertainment industry.