(A 2-page flyer in PDF format, referring to the recent Toronto event, is available.)
For nearly 20 years, cinema production and post-production has been based upon the conceptual model of film acquisition: Even if digitally acquired, imagery was typically processed using the Cineon/DPX model – technically, Cineon Printing Density (CPD) coding. That coding incorporates the technical parameters of film; in particular, the S‑shaped tone response and the colour crosstalk of film are built-into the image encoding. The CPD scheme has made CGI and VFX difficult.
Digital cinema cameras are now commonplace. Some of them generate CPD data (e.g., ARRI log C) comparable to a film scan. Others generate data comparable to HD video (BT.709/BT.1886), or are based upon HD video (Hypergamma). Still others use “log” formats of various kinds (Panalog, SI log90, Sony log, Red Log). DI houses and CGI/VFX facilities have to deal with image data in new forms.
The Academy of Motion Picture Arts and Sciences is standardizing a technique (formerly called IIF, now ACES) to acquire and process “scene-linear” data – that is, image data closely coupled to scene exposure. Colour transforms imposed during the DI process create the desired “look” and compensate for the viewing conditions of cinema. The scheme is being deployed commercially. Even without strict technical conformance to the various elements of the ACES system – the ACES colourspace, IDT, LMT, RRT, ODT – the concepts are important.
In this 1‑day Seminar, Charles Poynton will discuss the technical and visual requirements for acquisition and processing using the ACES scene-linear model. I will introduce the basic technical parameters of various camera encodings and describe their dynamic range and noise properties. I will outline how “picture rendering” must be imposed in the DI pipeline, for example, by the AMPAS reference rendering transform, RRT. I will describe the ACES colourspace (and its close relative, OCES), and describe the four key colour transforms in the scheme: IDT, LMT, RRT, and ODT. I will explain how the scene-linear model is applied to the DI pipeline, and how it aids CGI/VFX integration.