Wide Color Gamut Coverage of TVs
Rec.709, DCI-P3, Rec.2020
A TV’s wide color gamut coverage refers to how much of the new, larger color gamuts a TV can display. Wide color gamuts include a greater number of colors than what most current TVs can display, so the greater a TV’s coverage of a wide color gamut, the more colors a TV will be able to reproduce. This is one of the more exciting new developments in TV technology and should help a TV to create more colorful and lifelike images. This feature is useful for HDR media (see HDR vs SDR), like UHD Blu-rays and some streaming video.
For this category, we test whether a TV has an option to enable a wider color gamut, and how much of the DCI-P3 and Rec.2020 wide color gamuts the TV can cover.
When it matters
Wide color gamuts only really matter for HDR video sources like UHD Blu-rays and some streaming video, as only HDR sources are meant to take advantage of the ability to display more colors.
With compatible video, a wider color gamut than the standard Rec.709 offers a very noticeable difference. Above, you can compare the Samsung JS8500 with the wide color gamut feature disabled (left) to the Samsung JS8500 with the wide color gamut feature enabled (right). Both are playing an HDR test file. You can see that colors are deeper, richer when the feature is enabled than when it is not, and this is with incomplete coverage of the wider color space (92% DCI P3/68% of Rec.2020). Full coverage of either space would look even better.
Wide color gamut
This first evaluation is just to see whether a TV has an option to enable a wide color gamut, and how much this increases the color gamut of the TV. Again, this only matters for HDR video, and how much the results of this test matter depends on two things: whether a TV does include such a feature, and how much coverage of the wide color gamuts the TV is capable of when the feature is enabled.
For this test, we look in the TV’s menu and see if an option to enable a wide color gamut can be found. If it is possible, then we measure the color gamut and consider a threshold of 67% of Rec. 2020 uv coverage for wide color gamut support.
This test evaluates how much of the DCI P3 color gamut a TV is able to cover.
Of the two larger color spaces that will be included in upcoming TV models over the next few years, DCI P3 is the one that will be implemented the soonest, and it represents the basic color requirement of the HDR spec. To meet the minimum UHD Alliance requirements, a TV must be able to display over 90% of the DCI P3 color space. Because of this, our test for DCI P3 coverage is of greater immediate importance than our test for Rec.2020 coverage.
The main difference between DCI P3 and Rec.709 (the current standard color space) is that DCI P3 can display many more tones of green, though there is also a slight expansion to the number of red tones. The number of blue tones was unchanged. Altogether, it covers just over half of the visual spectrum and will provide a pretty significant increase in picture quality over Rec.709, which covers only about 35% of the visual spectrum.
For this test, we use the Colorimetry Research CR-250-RH spectrophotometer (connected to PC via USB) to analyze a series of six colors – red, green, blue, yellow, magenta, and cyan, all displayed at 75% luminosity and varying saturations– that are produced by the CalMAN 5 for Business calibration software, and displayed on the TV in an 18% window. We measure saturations of 20%, 40%, 60%, 80%, 95% and 100%. While conducting this test, we send in the HDR metadata (on supported TVs), we enable the wide color gamut feature on the TVs that have the option, and we also measure the TVs that lack that capability.
DCI P3 xy
The first number is the coverage area of the intersection between the DCI P3 space, and TV's boundaries, done in the CIE 1931 xy space. While the xy space isn't the best at representing the perceptual difference between colors, using it for the calculation of the area of coverage is a better approximation of the real gamut size than the uv below (source).
This is the intersection of the two areas, which means sometimes a TV with a wider gamut volume could have a lower number than one with a smaller volume if the TV is mostly outside the DCI P3.
In any cases though, both numbers are an approximation of the real gamut coverage because they are done in a 2D space, by intersecting areas. Ideally, we would measure the intersection of the gamut in 3D. However, this is practically impossible to do, because it would require taking millions of measurements (basically all colors), to create the exact volume covered by the TV.
DCI P3 uv
The second number is the same (intersection between DCI P3 and the TV's area), but done in CIE 1976 u' v' instead. As mentioned above, it isn't as good as an approximation for the real gamut. On LCD TVs, it will more often than not be a higher number than the xy coverage. Therefore, because it is a bigger number, this one is more often used by in the manufacturers' specs to boost them.
Sometimes, that number will be lower than the xy. For example, if the gamut is covering the green area well, but does poorly in the blue. The uv space reduce the importance of the green compared to the blue.
This test evaluates how much of the Rec.2020 color gamut a TV is able to cover.
There are no TVs that can come close to displaying all the colors within Rec.2020, and there likely won’t be for at least a few years. However, to help future-proof the technology, Rec.2020 support is already baked into the HDR spec. That means that the same genuine HDR media that fills the DCI P3 space on a compatible TV now, will in a few years also fill Rec.2020 on a TV supporting that larger space.
Similar to DCI P3, Rec.2020’s main gains are in the number of new tones of green that it will display, though it also offers improvements to the number of blue and red colors as well. Altogether, Rec.2020 will cover about 75% of the visual spectrum, which is a sizeable increase in coverage even over DCI P3.
We use the same process for analyzing Rec.2020 as we do for DCI P3, the difference being that the TV’s colors are evaluated as a percentage of the Rec.2020 space.
The first number is the coverage area of the intersection between the Rec.2020 space, and TV's boundaries, done in the CIE 1931 xy space. See above in the DCI P3 section, to learn about the difference between the xy number and the uv.
The second number is done in the CIE 1976 u' v' space. See above in the DCI P3 section, to learn about the difference between the xy number and the uv.
What a color gamut is
A color gamut (also known as a color space) is a range of colors found in the visual spectrum. Particular colors, one variation each of red, green, and blue, are established as the boundaries of a given range, and any colors that are found within those limits are considered part of that space.
Color gamuts are created by telecommunications standards organizations and help in establishing concrete specifications for what the TV must be capable of doing. To meet a given color gamut’s specifications, a TV must be able to display all of the colors included in that space.
At present, there are three main color gamuts that are important to TVs: Rec.709, DCI-P3 and Rec.2020.
Rec.709 is the current standard space required for every kind of widescreen home media available today, from DVDs to HD cable, Blu-rays to streaming video. Most HDTV and UHD TVs are not meant to display colors beyond those contained within this space.
Rec.709 is quite limited in terms of the amount of color it represents, only capturing just over a third of the visual spectrum. Of course, video still looks good, but upcoming media that take advantage of the larger color spaces will offer more variety to the color you see, offering greater detail and truer-to-life video.
How to get the best results
For most TVs, it is not necessary to make any adjustments to the settings to take advantage of a wide color gamut with HDR content. Simply leave the 'Color Gamut' or 'Color Space' option to 'Auto' for most brands.
- For the full HDR experience, you will need to enable the feature that increases the peak brightness of light objects on the screen. Note that not all TVs supporting the wide color gamut also have the option to enhance peak brightness.
- Because no TVs can fill either of the wide color spaces, it’s not possible to calibrate their color for those spaces. Their reproducible limits will not be able to match the established limits of the space, meaning there is no usable reference for calibration to work off of, and no way to judge when the calibration is “done.”
A TV’s wide color gamut coverage describes how many colors a TV can display. The greater the coverage of a wide color gamut, the more colors a TV can reproduce within that space. This feature is only really useful for HDR content, like UHD Blu-rays and some streaming videos, but it makes a big difference with those media – colors will look much more realistic than they do with most current TVs. For this category, we test for how much of the DCI P3 and Rec.2020 color gamuts the TV can cover.
For those TVs that have the option to do so, the wide color gamut feature should be enabled whenever HDR media is being played. It should be left off when a regular video is playing, as the colors will otherwise look oversaturated.
Questions & Answers
- Whether a TV has a wide color gamut option
- Whether that option improves coverage of the wide color gamuts
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