HDD First Look: Dolby's High Dynamic Range Imaging Technology

Posted Tue Dec 31, 2013 at 01:30 PM PST by
Dolby logo

By Michael S. Palmer

With CES 2014 set to begin on January 7, Dolby invited a few tech journalists to the lab to see a first look preview of a technology Dolby hopes will revolutionize the consumer display business. First, we sat down with Pat Griffis, Dolby Laboratories' Executive Director of Technology Strategy, Office of the CTO. 

While Dolby is best known for its advancements in sound technologies (Atmos being their latest innovation), the company realizes sound is only half the experience. This is why, a few years ago, they developed the Professional Reference Monitor, or PRM, for post production and professional color grading. They've also joined forces with the Cameron Pace Group to design glasses-free 3D display technology (which is, at present, separate from what we are about to discuss). And finally, Dolby has been experimenting with better codecs, bit rate efficiency, as well as understanding the science and technology of displays. 

Basically, if Dolby wants to make TV better, then they wanted to know:

  • Is it about more pixels (4K, etc)?
  • Is it about faster pixels (High Frame Rate, etc)? 
  • Or is it about better pixels? 

Dolby says all of the above, but what the heck are "better pixels" exactly? Well, over a series of focus groups and experiments, Dolby learned people preferred images that were 200 times brighter than current TV standards, and with 4,000 times more contrast. 

In short, Dolby thinks the keys to better TVs are brighter pixels as well as pixels with a much more dynamic contrast.

What are "NITS"?

Before we can talk about the demo and jump into Dolby's new high dynamic range imaging technology, we need to be on the same page about current standards, and a few necessary terms.

The first such term is a Nit, which is a measurement of light (similar to, but quite different from a foot-lambert). One Nit = one candela per square meter, which doesn't really help define a Nit. So here's some real world scenarios: if you point your peepers directly up at the sun (please don't), your corneas are frying under 1.6 billion Nits. A typical skylight lets in about 100 million Nits. A florescent light emits about 4,000 Nits. Even black asphalt, on a sunny day, reflects about 2,000 Nits. And way, way down at the very bottom of the spectrum, we have the distribution infrastructure for cinema projectors and CRT televisions. 

Cinemas (when projected properly) only come up to 50 Nits, where broadcast TV and Blu-ray top out at 100 Nits.

All of this to say, filmed entertainment, when displayed in cinemas and in the home, isn't exactly lifelike in terms of brightness levels. For example, have you ever taken a photograph inside a room where there are a lot of windows? Your eyes can see inside and outside perfectly, but with the camera, you're either going to "blow out" the windows, or by seeing outside, everything inside is too dark. Essentially, current generation displays are limited to make similar choices in terms of brightness levels and contrast.

You wouldn't think this is so terrible. The current standards have been around for decades. Why does it matter?

When you reduce brightness and dynamic range, you also rob yourself of reproducing certain colors. Check out these three slides of the various color spectrums (photos taken with an iPhone, so my apologies for the quality). The entirety of the visible color spectrum (what we can see) is the outer line. In each corner, you have Red, Green, or Blue. Somewhere in the middle, with enough of each color, you get "pure white." The first triangle inside All Visible Colors is called the "REC2020" standard, which represents all the colors reproducible by an upcoming laser projection technology. Note how many colors disappear from what we can actually see:

Then we have the "P3" standard, which represents all the colors reproducible in film (and digital cinema). We've lost even more:

Finally, we have the "REC 709" standard, which (despite the typo) represents all the colors Blu-ray currently reproduces:

I know. These charts don't really mean much, so I hope this helps: Blu-ray marks the best home entertainment distribution format currently available, right? Turns out Blu-ray's color spectrum is so limited that anytime you see a green highway sign, or one of the famous red London buses, the colors are incorrect. That's right, those particular shades of red and green do NOT exist in REC 709 Blu-ray, so the filmmakers -- when color grading for Blu-ray (and broadcast TV) -- have to cheat, but in doing so, brightness levels and contrast suffer. Meaning, when they find a replacement green or red, it's often much closer to white on the color spectrum and, when compared to the original uncompressed RAW footage captured during production, much more washed out. And when colors wash out, you're losing fine detail and apparent resolution. 

I hope that makes sense. It's a little technical and abstract, even for me, but just know the above color charts aren't flat pies, but rather tall towers to account for color AND relative brightness. Every limitation, every time you can't reproduce a color or a natural dynamic range, affects accuracy. This is basically why so many modern movies feature washed out white skies rather than bright blue ones (please forgive the simplicity). Moving on...

The Demo

At this point, we know TV and film are pretty limited in terms of accurately reproducing contrast and colors, but to demonstrate what this means for perceived picture quality, it was time for Dolby's demo.

In a room perfectly devoid of light, we watched HD footage shot on the ARRI Alexa digital cinema camera. The first part included an aluminum skinned WWII fighter plane flying over the Pacific Ocean as well as a woman in a white dress, standing under a blue sky in a field of blossoming flowers. The second part highlighted a Low Rider car club driving their vehicles in and out of a garage, as well as a mechanic doing some welding. All footage was uncompressed and color graded to Blu-ray's REC 709 standard and displayed on the aforementioned Dolby PRM 4200. To my eyes, and given the lack of compression, it looked even better than Blu-ray. 

Then it was time to watch the footage again, with an enhanced dynamic range, on a modified PRM called the Dolby Experimental Display. This Experimental Display had the exact same 1080p LCD panel as the standard model (same number of pixels, same resolution), but was upgraded to emit a peak luminance of 4,000 Nits (it's lowest setting was 0.005 Nits).

[It's important to note that Dolby is NOT getting into the consumer display production business, but they needed the Experimental Monitor to show off what they're doing.]

We watched the enhanced footage by itself as well as side-by-side with the original color grading. Our eyes are naturally attracted to brighter imagery (thus the reason why big box stores set all their displays to "Torch Mode"), so I tried my best to make sure appreciable differences were not due to the increased brightness. That said, the enhanced dynamic range was pretty incredible. The same uncompressed footage had been color graded to something closer to the P3 standard (though when Dolby officially announces this technology at CES -- more on this below -- it will be capable of up to 2020) and it was stunning all around. More colors, more lifelike details, more everything. And to prove it wasn't just its own footage, Dolby showed us clips from 'Samsara', which when given the wider dynamic range, were even more vivid and eye popping than Dolby's materials.

I've never really thought of "color" as being important to resolution, but the more accurate the colors on display, the more details in the images I could see. Here's one example screen grab, supplied by Dolby, that approximates the experience. Like all screen grabs, this image is limited by the inherent compression issues of making a jpeg file (click on the link to see the full size image):

Flowerfield-Standard left-New Dolby Imaging Tech right.jpg

I was actually reticent to post the above images because some of you will look at this and already think this tech is bogus, or doesn't make any difference. If you're thinking this, that's okay, I get it. You're limited to my vague descriptions and one screen grab. But please, please, just wait for a chance to see this technology with your own eyes before judging one way or another. More so than with Blu-rays, this screengrab can't compete with the real thing.

Because in person... When  you are sitting in front of the moving images, it's a revelation. 

Here are some improvements I noted:

  • In REC 709 (standard Blu-ray), oranges and yellows on brightly lit flowers would wash out. They seem fine when you're watching them, but head to head, the enhanced dynamic range versions were brighter and bolder and more colorful. With the added colors, I could see more depth and details in the petals. 

  • In the airplane sequences, the REC 709 color graded sun was a giant, white orb. Reflections off the plane and ocean surface shimmered brightly. On the Experimental Display, the the sun was more lifelike (less blown out) and the plane's aluminum skin was more crisp -- you could see individual rivets -- because there was no need to reduce the brightness to see objects around the plane. 

  • The REC 709 Low Riders weren't as colorful, and when they drove out of garages, you couldn't see shadow details. In the enhanced footage, you could see shadow details akin to real life. 

  • The welder footage was remarkable too. What was, in REC 709 limited to 100 Nits, another white orb, became, on the Experimental Display, a distinct pinpoint of light, which allowed us to see details on the welder's face mask and gloves.

  • Lastly, it's important to note that in no way does enhancing contrast and brightness make footage feel like TruMotion or any of the frame rate interpolation technologies from TVs and/or anything like 'The Hobbit.'

What Does This Mean For You?

Sure, Dolby turned a few of there super-expensive professional displays into experimental demo displays, and piped in uncompressed video that was professionally color graded to take advantage of these one-off televisions, but is "High Dynamic Range Imaging" the next 3D or 4K? Another niche, expensive product where I have to replace all my gear?

Sort of? Maybe? I don't know yet.

Dolby thinks their new technology could actually be the thing that helps 4K really take off. But regardless of pixel counts and competing technologies, Dolby wants to create an entire "ecosystem," or pipeline, that goes directly from content creators to your home cinema without messing up what's already working.

Starting at the top, today's color grading systems (and digital cinema cameras) already work at a much higher quality than what displays are capable of. The problem is that, after the film is made and when it's time to send it out for Blu-ray or TV broadcast, the limitations are set by a television technology no one uses anymore. 

So Dolby is developing a new Plugin for color grading systems that will allow content creators to output their projects in a "container" (think codec) that is fully backwards compatible -- it will work with 4K, 1080p, and 720p -- but includes "enhancement information" on top of current standards to take advantage of new displays with higher peak luminance levels and wider contrast ratios. Meaning, the content will play on current technology and look pretty good, but will look even better on new gear.

Another way of putting it: Dolby hopes to enhance the way content is produced and distributed, to free its inherent limitations, without making the consumers change anything. Interestingly, many current gen flat panel displays are capable of 300-400 Nits, with one Sharp model measuring up to 1,000 Nits. Displays are already brighter, but because the content is graded for 100 Nits, if you bump up the brightness (see the aforementioned "Torch Mode"), the colors look like crap. Therefore, thanks to HDMI, when content in Dolby's new container hits the streets (or air), some of the current displays *could* see improved contrast and colors (though not all).

That said, if you want the full benefits of Dolby's innovation, you'll need a new display from one of Dolby's impending partners. Though they wouldn't say what products, or with which companies, Dolby seems geared up to be making some big announcements at CES 2014. They'll likely -- again, this is my guess -- team with one or more display manufacturers, as well as one or more Hollywood Studios, to announce the "ecosystem" that will take film and/or TV content, put it out on a Blu-ray (or perhaps via a streaming box) to a new UHD (4K) display capable of producing upwards of 10,000 Nits and a 1,000,000:1 native contrast ratio (compared to current generation display, which are color graded to more like 1,000:1).

Again, I don't know if these new displays will be massively more expensive than standard sets. Or when they will be available. Or what companies will be delivering content. Or what method (optical, streaming broadcast) said content will be distributed. There are a lot of practical chicken-and-egg questions that may or may not have already been solved. But if our movies and TV shows can reap the benefits of "better pixels," then I'm very excited to see what High Dynamic Range Imaging Technology will mean for home cinema enthusiasts and hopefully general consumers as well.

Blu-rays already look and sound fantastic, but they can definitely be improved. If we're already hearing the bit-for-bit identical soundtrack master, Dolby's innovation could be the closest thing to being on set while the film is in production.

For More Information 

Check out this blog, Is Your TV Bright Enough, by Mike Rockwell, Executive Vice President, Advanced Technology Group, Dolby Laboratories, or Scott Wilkinson's piece over at AVS Forum.

See what people are saying about this story in our forums area, or check out other recent discussions.

Tags: Dolby (all tags)