Issue link: http://digital.copcomm.com/i/1006097
www.postmagazine.com 34 POST JULY 2018 www.postmagazine.com 34 POST JULY 2018 studios must accommodate among a myriad of distribution outlets. Thus, the "look" of the HDR master may or may not be getting the attention it would if it were part of the entire production workflow from acquisition through post production. And it is often incumbent upon colorists to interpret the creative intent of the directors and DPs, in lieu of their direct input, when creating HDR versions for distribution. Currently, turning SDR content into HDR content is generally accomplished by creating a digital master that is encoded in the SMPTE ST2084 standard for downstream transform to whichever HDR formats the content being delivered needs to support. SMPTE ST2084, also known as PQ — short for Perceptual Quantization — is a gamma curve that is designed to efficiently allocate the data bits in a video signal to closely approximate the way the human eye per- ceives changes in relative brightness. DISTRIBUTION FORMATS At present, there are a handful of competing HDR distribution formats. These include HDR10 and the new HDR10+, Dolby Vision, HLG (Hybrid Log Gamma) and SL-HDR1 (Technicolor). I won't get into extensive technical comparisons between these formats as that is another article. However, there are essentially two camps as it pertains to the best way to implement the wider gamma curve required to distribute HDR images. HDR10, HDR10+ and Dolby Vision are all based on the PQ curve as defined in the SMPTE ST2084 standard. HDR10 applies the PQ gamma curve uniformly across the entire content stream. Alternatively, Dolby Vision and HDR10+ use dynamic metadata to map scene-to-scene dynamic range to the capabilities of the display it is being viewed on, provided the display supports the encoded HDR format. Additionally, Dolby Vision chose a wider 12-bit color space while HDR10 and 10+ utilize 10-bit color. HLG (Hybrid Log Gamma) and SL-HDR1 are both designed primarily to address the challenges of HDR broadcast production and distribution to provide better backward compatibility (the Hybrid part). HLG is essentially an "enhanced" gamma curve designed to more closely mimic standard gamma 2.4 at the lower end of the curve while extending luminance latitude on the higher end so that signals will look better on TVs with HDR capability - while still looking like they should on older SDR sets. Technicolor's SL-HDR1 is a vari- ant that adds a single layer of metadata to adapt to the HDR displays higher brightness capabilities to render more accurate hue and contrast values. HDR10 has the widest support currently — largely because it was mandated as part of the UHD Blu-ray standard. Most streaming services use HDR10. Netflix and Apple TV stream in both Dolby Vision and HDR10 while Amazon streams in HDR10, HDR10+, and Dolby Vision. Other providers like Fandango, Google Play, Vudu, YouTube, and more support at least HDR10. As you can imagine, this minefield of multiple HDR formats and the econom- ics of mastering and distributing them — including the high cost of professional HDR reference displays capable of reproducing the "better pixels" these for- mats offer - has made mastering HDR content both complicated and challeng- ing for post-production facilities. At present, there are only a handful of HDR reference displays available that are meeting most, if not all, of these requirements. High-end offerings in the 30-inch size-range from Canon, Eizo, Flanders Scientific, Postium, Sony and TVLogic offer varying levels of 4K HDR reference performance vs. cost and all are priced starting in the tens of thousands of dollars. Since no content provider or consumer television manufacturer supports all HDR formats (go figure), post facilities need reference displays capable of the range of specifications found in the various formats. And they have to master HDR content that looks good on consumer televisions with a range of capabili- ties and limitations. I asked David Abrams — who's company, Avical, provides display calibration and consultation services to Hollywood's top studios and post production facil- ities — to comment on the greatest challenges his customers face when tasked with mastering HDR content. "The biggest issue my clients face is both the size and cost of HDR refer- ence displays. At around 30 inches, the best HDR reference monitors that are currently available are great for colorists to use at their workstations. However, when it comes time for the creative team to review, the size of the display can become limiting." Abrams continues, "And with the cost of these monitors hitting $30K to $50K and beyond, it's a real challenge for post facilities to discern the right combination of price vs. performance when making an investment in the technology." As is often the case with new innovations, products can be expensive until they can benefit from economies of scale. And like most technologies, flat panel displays are ever evolving. Organic LED displays continue to improve. Ubiquitous LCD technology is being refined and re-imagined to adapt to the rigors of HDR imaging. MicroLED is a promising technology for large screen theatrical displays. However, scaling it down to 55-inch and 65-inch TV sized screens is neither economically or technically feasible at present. In the near term, HDR formats will battle for dominance while Hollywood studios, theaters, and content producers move further into the HDR ecosystem, gradually bringing the promise of "better pixels" to a wider audience that, when it all comes together, will experience entertainment in a whole new light. Wes Donahue is VP of sales & marketing, Postium America, wes@postiuma- merica.com, www.postiumamerica.com 4K HDR AND Netflix's GLOW