Six Tips for Simpler HDR Workflows posted: 12/02/2020 Working in HDR is quickly becoming a requirement for many creative professionals from production through to post, even if content will be delivered in SDR. However, HDR is still an emerging approach for creating moving imagery with the most dynamic range and richest color delivery possible and can pose challenges for pros throughout the production chain if unfamiliar with key concepts to keep in mind. To help cut through some of the confusion, we've compiled a list of six things to consider when building an HDR workflow that will make your job that much easier.
1. Determine your intended audience and delivery destination
Are you producing or editing content that will be viewed on large-scale in-venue displays, mobile devices, living room TV-sets or cinema screens? How and where your content will play should dictate the production approaches you choose as well as nit level expectations, color spaces and transformations between formats. There are four main format choices: HLG and PQ HDR formats and standard SDR for both broadcast and cinema purposes, plus associated color gamut delivery. HLG is well suited to live production and broadcast pipelines throughout the production chain, as HDR metadata does not need to be attached to the signal, and both HDR and SDR can be accommodated within a single baseband pipeline. For other delivery methods where PQ may be preferred for transmission across SDI, the forthcoming SMPTE ST 2094 spec will assist. In the meantime, you can adhere to PQ delivery with file-based metadata or use analysis and transform tools at various points in your chain until delivering a final with your chosen format, whether HDR10, DV, or HDR10+. The key to a successful delivery is to ensure that you work within the color gamut requirements of the delivery platform as below. As always, starting with the widest ranges possible from source is key, whether RAW materials for file-based workflows or Log for live baseband feeds into HDR transform tools like AJA's FS-HDR.
2. Consider your color space bucket
Your color space bucket will impact the tools you use and what you want to look for in terms of your final look, as well as how you will monitor throughout the process. Many studios and platforms require a full ACES workflow and an ACES final master with a conform to P3 for a delivery master, It's therefore not uncommon to do a master for BT.2020 for future proofing and then produce a trim for P3 delivery needs with colors clamped to the P3 space.
3. Find the right camera system
Like any production, all HDR projects start at capture, which means the HDR delivery method and color space you select will help play a role in your camera choice. For instance, when working on a live production, a Grass Valley camera outputting HLG might be a good option, as would a Sony camera outputting HLG or S-Log. For a traditional episodic or proAV project, a camera with as wide a dynamic range as possible is always advantageous. In this case, it's ideal to have a system that can deliver Log formats and convert to HDR color and dynamic range specifications that match your production and color space needs in real time as with AJA's FS-HDR. In other cases, a file-based workflow that uses original RAW files might benefit from an application like Colorfront's Transkoder to convert files into Log and other formats for further manipulation or straight RAW to uncompressed video or codecs with color gamut and nit levels for PQ or HLG included.
4. Dont forget monitoring and analysis
The key to great quality control (QC) throughout the production process is getting an accurate idea of what your final product will look like from production through to editing, VFX and color grading - especially since HDR makes so much more detail available within luminous range and color gamut. The picture you see when monitoring will be a guiding factor in the areas that you choose to emphasize or deemphasize, which is why an HDR-equipped on-set monitoring and analysis system is a worthwhile investment; it can help guide these decisions and others, even when you don't have access to an HDR capable display. Technology like AJA's HDR Image Analyzer - available in both a 3G configuration for up to 4K workflows and a 12G version with up to full 8K support - can provide a huge assist on-set, allowing you to take an SDI monitor or output tap from your camera and accurately monitor its color gamut output and nit levels. For the most flexibility and assurance that your creative decisions are going to work for your final product, adding an FS-HDR for transformations from the camera signal into a color space and format setting that you intend to deliver down the road, and feeding its output into the HDR Image Analyzer will provide an accurate view of the result of your decisions. This is vital in ensuring the exposure is set correctly, your lighting choices, especially for backgrounds, are balanced as intended, and makeup and props are accounted for when delivering to multiple HDR and SDR platforms. If you find an error, the HDR Image Analyzer makes it easy to identify areas of concern where the color gamut or nit level may be exceeded prior to post, QC and before delivery.
5. Be prepared to monitor in HDR and SDR
It's not all that uncommon today to monitor content in both SDR and HDR, which may seem complex but is quite easy when using simple devices like AJA's Mini-Converters for monitoring. The small devices support monitoring of SDI outputs from various devices, offering a path from SDI camera or recorder outputs for instance to HDMI monitors where various HDR formats can be set. This way, you know whether or not you're correctly exposing the level of background detail that is likely to be seen in HDR and you can quickly
