Twenty years ago, there was a clear divide between how you shot and finished a project for Cinema compared to the typical workflows used in broadcast TV. With the advent of streaming services that provide 4K/UHD to a broad audience the lines are now blurred between these two worlds.
This article was first published as part of Essential Guide: HDR For Cinematography
Further, the technology to provide high resolution and high dynamic range cameras and displays is today considered main-stream and accessible by even modest production budgets. The challenge now is how to up-level the skills and tools of a much larger population of production teams to support this transition.
As a longtime provider of tools for broadcast television, Telestream (as Tektronix) pioneered all the measurement displays that are familiar to broadcasters but were geared to a world that was constrained by 1960s television –over the air signals received by CRTs.
Brightness levels were limited to the technology of the CRT and the color had to be constrained to fit into the available broadcast spectrum. Consequently, the production jobs were about making sure you balanced your blacks, kept your whites from clipping and then didn’t violate the government regulations for color gamut. The new standards for UHD that provide higher resolution, a larger dynamic range, and a wider gamut of colors have pushed past these boundaries to create amazing pictures, but they’ve also pushed past the usefulness of tools that were used fifty years ago. As a result, Telestream has worked on a next generation toolset that can be used to get the most out of what UHD can provide.
Traditional Vs New HDR/WCG Tools
Broadcast production teams are familiar with traditional waveform and picture analysis, even though HDR workflows will require additional new analysis tools, enhancements to traditional tools also helps production teams’ transition. PRISM has enhanced the traditional tools to support HDR/WCG including waveform and picture analysis with upgraded graticules and cursors to support multiple gamma types (SMPTE PQ 2084, HLG, plus camera gammas like Slog2 and Slog3). Readouts for the graticules and cursors are available in nits and stops, in addition to the traditional IRE percentage and millivolts. PRISM adds the ability to view an HDR trace display and picture converted to SDR for a quick SDR workflow check. This enables an engineer or operator to view HDR and SDR traces and pictures side by side on a four-tile display, to ensure video will display well on both television types.
PRISM then adds new HDR/WCG monitor and analysis tools. The stop-waveform is a new way to display the luminance levels in terms of linear display light or linear light. Changes in luminance level are represented in the stop-waveform in a linear manner; for linear display of PQ and HLG workflows in nits; and linear scene for Slog2/3 camera gamma in stops. There’s no need to convert from mV or IRE, light levels are displayed to easily determine the dynamic range or stop difference between two points on an image. It’s very powerful when used with the Light Meter to cross check and set light levels.
Broadcast operations can identify false colored pictures in their HDR workflows with a new highly configurable false color display with up to 10 false color regions. An optional false color meter shows the currently selected false color regions and their selected limits.
False color display to confirm with standards of brightness, percent HDR and dynamic range of the scene.
The traditional tool for color matching between scenes, setting skin tones, and brand consistency in post-production, is the Vectorscope. When working with wide color gamuts across multiple color spaces, the Vectorscope has limitations, because moving across color spaces has the effect of rotating the color points on the vector trace. To provide a true representation of what is happening in each color space, Telestream has introduced the CIE chart display based on CIE 1931 color space. The PRISM CIE chart display shows regions for Rec 709, DCI-P3 and Rec 2020 enabling operations team to ensure video color gamut are within these standards.
HDR production is realizing that light level artistic intent should not overdrive the amount of display light, while taking advantage of HDR capabilities to display more detail in darker scenes. A new tool in PRISM provides a readout of the minimum light level (in nits) for the brightest and darkest sets of pixels as a percentage of the screen to confirm creative intent and ensure TV compatibility.
Streaming providers like Netflix are increasingly requiring Post facilities to constrain colors to the DCI-P3 colorspace, even when content is encoded in a BT.2020 container to make it easier to remaster in the future when 2020 capable displays are available. A third false color mode from Telestream helps to verify this at the production QC stage, with flexible false color pixel detection outside the BT.709 colorspace or outside the DCI-P3 colorspace when working in a BT.2020 container.
When it comes to HDR and WCG, the workflow of cinema, television and live production are beginning to converge, and objective measurements are required to ensure compliance and to avoid creating content that can’t easily be fixed in post-production. Telestream next generation tools can support the existing traditional workflow, and are ready to enable product teams in cinema, television and live production to support the transition and production needs for updated HDR and WCG workflows.
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