There are three ways that television displays can be improved, two of which you’re probably already familiar with: you can up the density of the pixels or increase the refresh rate. But Dolby has taken to improving the third factor: It’s building a better and brighter pixel.
What Is Dolby Vision?
There’s currently a disconnect between what content creators film and what ends up being displayed on the consumer’s television or movie screen. While current high-end cameras like the Red Epic and the Arri Alexa can capture scenes with a massive amount of detail, colour depth, and clarity that’s beginning to rival human visual capabilities, the international standards for television broadcasts and theatre projectors are stuck in the last century. The first part of last century.
“The standards for film were defined at a time when, the main business viewpoint was, ‘what was the slowest I can move a film strip through the shutter of the camera and still call it motion — that’s why we settled on 24 fps,” explained Patrick Griffis, Executive Director, Office of the CTO, of Dolby Labs. “And brightness was set on the notion of ‘what is the brightest bulb I can put in front of that film without melting it?'”
That means that the standard for cinema projectors today equates to roughly 48 nits (a unit of brightness). Television, on the other hand, is standardized to 100 nits with a colour palette based on the old CRT technology’s rare earth phosphors. “We have this interesting conundrum in that television is twice as bright as cinema, but the colours are based on what rare earth phosphors could do,” Griffis continued. “Film is half as bright but the colours are based on film emulsion” and therefore cover a broader swath of the spectrum.
The grey horseshoe shape in the diagram you see below represents all of the possible colours in the CIE 1931 chromaticity range — that is, the first mathematically defined colour spaces which were generated by the International Commission on Illumination (CIE) in 1931, hence the name — while the tiny colourful triangle represents the available colour range for old CRT monitors using rare earth phosphors. Basically, if you make any mixture of the primary red, green, and blue colours within that range to create any other intermediary colour. Mix them exactly right and you get white.
“People mistakenly call it a colour space,” Griffis said. “It’s actually a two-dimensional plane and what you really need to know if you’re a creative is this is your palette of colours but what the horseshoe chart doesn’t tell you is how bright each colour can get. White will always be the brightest because it’s the sum of all three primary colours.”
“So we’ve got this interesting problem that we’ve lived with for the better part of 60 years where the colours in film go out farther but you can’t get as bright and in television there are less colours but you can get brighter,” Griffis told Gizmodo. “And the practical consequence of that for the content creator is that the Red Bus of London that looked so great in the movie looks like Campbell’s Tomato Soup on the Blu-ray unless someone does something.”
What’s more, CRTs form the standard basis of virtually every modern display — televisions, cable broadcast, even Blu-rays. This means that even though we’ve long since abandoned CRTs for flat screens, we’ve still long been hamstrung by these outdated standards. This delay is due in part to the fact that they’re international standards and have been in place for so long that the effort necessary to convert or retrofit existing technology to a new standard would be nearly impossible — akin to switching the standard British electrical outlet for the American standard, there’s simply too much existing infrastructure to easily swap one for the other. Thankfully, however, the migration from antiquated colouring schemes based on technologies from the start of the 20th century (and film itself, for that matter) to modern digital methods is slowly but surely under way.
And that brings us to what Dolby Vision actually is. Dolby Labs defines the system as:
Dolby Vision helps content creators and TV manufacturers deliver true-to-life brightness, colours, and contrast. It augments the fidelity of Ultra HD and HD video signals for over-the-top online streaming, broadcast, and gaming applications by maintaining and reproducing the dynamic range and colour palette of the original content.
It’s an end-to-end method of preserving the image and colour quality of content from creator camera to your eyeballs. “Our goal is to take the artistic intent of the content creator and preserve it as much as possible while meeting the realities of delivering an efficient signal,” Griffis said. That means more than just working with TV manufacturers like Sharp and TCL to create Dolby Vision-enabled sets, it also entails working with industry trade groups to update the nit standards, and working with major production studios and directors to actually adopt the technology in their shoots.
Essentially, it widens the colour gamut pipeline, reducing the loss of image quality as it is broadcast. It allows for much brighter pictures — on the order of 10 to 20 thousand nits compared to today’s 100 nit standard — boosts dynamic contrast by a couple orders of magnitude, and generates brighter, more lifelike colours that don’t wash out under the added brightness.
It is impossible to accurately capture the difference Dolby Vision makes by using regular photography. It’s best seen live. But here’s a taste of the difference between a display using Dolby Vision (RIGHT) and standard HD video (LEFT).
Contrast is the comparative measure of the brightest white in a given scene against the darkest black. “It’s an amazing dynamic range that we as humans experience every day — from sunlight at 1.6 billion nits down to absolute black at 0 nits, though you can’t actually see anything in that, but even starlight is .00001 nits,” said Griffis. And we can certainly see both the sun during the day and stars on a moonless night. “So we humans every day deal with a dynamic range of 10-6 and 109 nits — that’s 15 orders of magnitude for dynamic range. Now while we can see from sunlight to starlight, we can’t actually see them at the same time.”
A more practical real-world range, according to Dolby’s research, is anywhere from 4000-6000 nits for a scene’s average brightness with up to a 100,000 to 1 dynamic contrast ratio — the brightest white is 100,000 times brighter, in terms of nits, than the deepest onscreen black. “We can typically see in any ambient about 5 to 6 orders of dynamic range,” explained Griffis.
The current standard for television is nowhere near that, instead averaging a ratio of just 2,000 to 1. This clips the quality of the image quite noticeably. The lack of contrast is how you can tell you’re staring at a screen and not through a window. Dolby Vision enabled displays will reportedly offer contrast ratios 100 times better than modern HD televisions.
Contrast ratio grows out of a set’s overall brightness, so if the whitest white is only 100 nits, you’ve already severely limited the bounds of the ratio. Sure, the picture can be made brighter but that comes at the expense of black levels and colour saturation (which means there are minimal amounts of white in it).
Dolby’s market research suggests that 90 per cent of the study participants preferred the picture of a TV that went as high as 20,000 nits — roughly the light output of a 100W bulb — compared to the current 100 nit standard. “Viewers, if they had the choice,” said Griffis, “they would want a picture 200 times brighter than what they have now. So we find it kind of interesting in the discussion of 2K versus 4K — which is really just 2MP versus 8MP — that’s a 4x improvement in spatial resolution but we’re off by two orders of magnitude in terms of brightness.” And the benefits of a TV that is just that much brighter extend also to contrast ratio and colour depth.
“As colours get more and more white,” as Griffis explains, “they tend to turn paisley and pastel.” So the highly saturated yellow in the flower (below left) measures 14,000 nits — that’s 140 times brighter than what today’s TVs can produce. So, to compensate, today’s TVs instead either bump up the brightness (basically adding additional white to the image) that simultaneously washes out the colour saturation or lower the brightness of that yellow to around 80 nits, which muddies the colour. “The real world has this tremendous dynamic range. We’re able to see it but until recently, our technology couldn’t.”
This is why, as Griffis points out, the Red Bus of London looks like tomato soup when it is formatted for Blu-ray — the brightness and colour range don’t extend far enough in either direction to allow for the accurate representation of the iconic British transports. You simply can’t have both accurate, saturated colour and a bright, wide dynamic contrast ratio under current television standards, but you can with Dolby Vision.
As you can see in the image above, the 4000 nit HD Dolby Vision set on the left is able to display brighter, more saturated, and vivid colours with increased brightness and dynamic range compared to the 100 nit HD reference set on the right.
This added brightness allows for a wider colour gamut (or range) that more accurately represents colours found in the real world and should decidedly increase the quality of broadcast footage. “If we’re going to try and achieve the holy grail of matching the capabilities of the human visual system, our new marching orders are 20,000 nits, not 100,” Griffis told Gizmodo. “And ideally we want to get more of the colours the human eye can see.”
So What Now?
A new set of standards — dubbed BT rec 2020 — has recently been adopted by the International Telecommunications Union (the folks who establish these international display standards) that is based on the most recent advances in Ultra High Definition technologies, specifically the use of lasers to generate pixel colours rather than white light shown through rare earth phosphors. These new standards are helping pave the way for even higher performing sets.
But Griffis explains, it’s more than just packing in more pixels and boosting the refresh rate. The quality of the pixels themselves must improve. Dolby Vision promises pixels with 200 times the brightness of today’s HD TVs with a 4000:1 increase in dynamic contrast, more saturated colours and deeper colour volumes.
“We’ve been so focused on the ‘more’,” Griffis said, “that we forgot to make them better.”
And it doesn’t appear that we’ll have to wait too long for the technology either. Dolby officially unveiled the system at CES this January, and is already working with manufacturers to integrate the system into upcoming sets. “The first Dolby Vision TVs will also be 4K TVs” Roland Vlaicu, Sr. Director of Broadcast Imaging for Dolby Labs, told Gizmodo.
Gizmodo was afforded a brief in-person demonstration using the comparative televisions in the image above. The images on both sets are displayed from the same Blu-ray source but the set on the left is a 4000 max nit Dolby Vision-enabled HD display while the one on the right is a standard 100 nit HD reference set. From the moment the demo started to play, the difference in image quality was obvious. The Dolby-enabled display was simply jaw-dropping. It looked so much better in fact, that I almost figured it to be a higher-resolution stream even though I knew it was playing from the same source as the reference monitor.
This new method does have a slight bandwidth cost, however. See, the visual signal can be split in post production between the standard, 100 nit HD signal and an additional modifying signal that carries the data for the increased brightness and colour palettes. This allows broadcasters, in the early days of the upcoming rollout, to keep offering the normal HD signal over cable or streaming for folks without DV-enabled sets but offer a higher quality picture for those with the new TVs — much like what Netflix is doing with House of Cards in 4K. This extra bit of signal, however, will consume an extra 15 per cent of your bandwidth and with major ISP’s now rumbling about data caps on home networks, that 15 per cent could suddenly become very valuable.
What’s more, while Dolby is lining up some of the biggest names in Hollywood, as well as throughout the broadcast and manufacturing industry, the system is by no means a sure hit just yet. There are a number of distribution and manufacturing factors that still need to be addressed before the system goes live. There’s also the small chance that Dolby Vision could go the way of Betamax or 3D — a fantastic idea that just never really hit it off with consumers and winds up forgotten or just one more badge on the bezel of the TV set. However, from what Dolby shared with us and after viewing the performance of the test set first hand, I’m not really sure how it won’t be a massive hit.
So while the current focus of television makers is more and faster pixels, they aren’t the only means of improving image quality. Thanks to the passage of updated standards and Dolby’s research, image quality as a whole could soon be better than we’d ever imagined. Get ready, the quality of your next home television’s image will amaze you.