Dynamic Tone Mapping Update
Sound & Vision|February - March 2020
Dynamic Tone Mapping Update
JVC DLA-NX9 D-ILA Projector
Kris Deering

In a departure for JVC, the company didn’t announce new D-ILA projector models at CEDIA Expo in September 2019. Instead, JVC’s key announcement at the show was a firmware update for the native 4K projector line it had unveiled at the previous CEDIA Expo in 2018. (Supported models include the DLA-NX9, DLA-NX7, DLA-NX5, DLA-RS3000, DLA-RS2000, and DLA-RS1000.) This update adds new features including proper 16x9 internal scaling when using a Panamorph “DCR” anamorphic lens (labeled as Anamorphic D) and new screen offsets for calibration purposes. But the most beneficial update by far is dynamic tone mapping, a feature that sets JVC apart as the only front projection brand on the market to offer a true “frame by frame” solution (LG’s HU85LA ultra-short-throw projector also features frame by frame tone mapping) for displaying HDR10 content.

A STATIC APPROACH

Projector owners so far have faced an uphill battle to optimize image quality for HDR sources. That’s mainly because HDR formats were developed not with consumer projection in mind, but rather flat-panel TVs capable of delivering massive light output. But even knowing the brightness limitations of their displays, projector owners may also want to take advantage of improvements offered by HDR such as higher video bit-depth and wide color gamut.

For a projector to work with HDR, it must employ what is known as a “tone map.” In a nutshell, this is a method for compressing a large amount of video dynamic range into the smaller space that the projector is capable of reproducing. Unfortunately, there’s no standard for tone mapping, so each manufacturer brings a different approach to the process.

If you look at HDR-capable projectors available today, they all employ some variation of what is known as a “static tone map.” This basically means that the HDR signal is stuffed into a single, fixed video range that’s typically based on the highest expected video level the content contains. Ultimately, this information is very difficult to predict—while some HDR programs provide metadata that conveys the correct peak video level, with others it may be wrong or missing entirely.

Regardless of how the static tone map is created, all images in the program that are less bright than the portion containing the highest video level are compromised. Here’s how that happens. The tone map applies to the program’s brightest point so that highlight detail in the image won’t be clipped when that particular scene is displayed. But that moment may only represent a few seconds of the entire movie, and because the video signal now has extra headroom added to it, the remainder of the program appears dimmer than it should. Essentially, dynamic range—something that’s already an issue with projectors due to their limited light output compared with flat-panel TVs— is being wasted to accommodate a single moment of peak brightness.

DYNAMIC DUO

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February - March 2020