Report on the Dolby Workshop held on 12 November

Workshop “Preserving Artistic Intent with Dolby Vision HDR”
Ian Lowe reminds the audience that HDR is a tool that is also capable of creating SDR images with a greater ability to reproduce specular lights and greater colour saturation, which would otherwise be impossible in SDR (colourful bright skies, neon or fluorescent type lights). All RAW or equivalent cameras that record a signal of 12 bits minimum allow for HDR filming and the curve used by Dolby (PQ ST 2084) is a Log signal. HDR is just a question of the visualization made possible by new screens and projectors that have superior dynamic range.

In order to shoot in HDR, he recommends using a lightmeter to adjust exposure to a neutral grey (at the centre of the sensor’s dynamic range) which allows you to have a latitude of ±6 f-stops. You have to be careful not to “clip off” the high and low values. Better contrast creates the impression of greater sharpness, so you have to be careful with makeup, costumes (with shiny and reflective material), and sets (a bit like when we went from SD to HD). HDR monitoring must be performed on set to best judge the density interaction between the actors and the backgrounds (lights inside the frame, windows, backlighting effects…).
The increase in contrast also makes more details in low densities visible (whether this is desired or not).
The Dolby Vision workflow is based on an analysis of each shot graded at maximum, minimum and average luminescence, which generates metadata that will be conveyed all the way through to release, which allows properly-equipped television sets and projectors to best adjust the dynamic range of the signal being displayed. Values set in grading (from HDR to SDR) will also enable the preservation of artistic intent on all types of displays. This adjustment, called “trim pass”, is performed by the colorist on different types of outputs (Rec 709, HDR 10).
The presentation ended with the comment that there are currently over 2,000 films and television series graded in Dolby Vision and that it is available from the majority of Internet content providers (Netflix, Amazon, Disney +, Studio Canal, Apple TV+, etc.)

Tina Eckman began the discussion with Alex Gascoigne, colourist at Technicolor, who has supervised series such as “Chernobyl” and “Black Mirror”. He has been with Technicolor for 12 years and began his first trials with HDR in 2016. He reminded the audience that today’s HDR colour grading process is nothing like photography multi-exposure. Our digital cinema cameras are all native HDR (due to their dynamic range greater than 12 f-stops). He always presents a final HDR version of his tests, as well as an SDR version. He prefers to begin doing the first final grading on the HDR version. It’s important not to distract the viewer’s attention with the bright lights present in the frame. He prefers to grade in the camera manufacturer’s wide colour gamut. For VFX exchanges, he uses ACES and feels it is absolutely necessary for all VFX to be outfitted with an HDR monitor.
After spending on average three days doing the HDR grading for each episode, his advice is to begin work on the SDR version, which takes between a half-day and two days, in function of the images, after having let the weekend go by. You should never compare the two versions, because the SDR version will always look disappointing.
His grading room is equipped with a Dolby Pulsar monitor capable of 4,000 nits, and a “client” television set at 1,000 nits even with light in the room !

(Translated from French by A. Baron-Raiffe)