Colour Volume: What It Is and Why It Matters for TV

Samsung Electronics’ 2017 QLED TV recently received verification from world-class testing and certification association, Verband Deutscher Elektrotechniker (VDE), for its ability to produce ‘100 percent colour volume.’ The designation, a first for any global TV manufacturer, illustrates how colour volume is quickly becoming an effective way to measure the precision of colours.

Defined as a three-dimensional representation that illustrates the colour reproduction capacity of a display at all of its luminance levels, colour volume is also an important standard for ensuring that content is displayed in the way the producer intended. But what makes it different than other colour standards? Let’s take a closer look at this new measurement of colour.

From SDR to HDR: Measuring Colours Accurately

Many television colour standards, which were defined in the days of CRT TVs, are stuck at an outdated 100 nits. As a result, displays were not able to express colours accurately when reproducing videos and images according to these standards.

With more recent displays, beginning with the world’s first commercialized HDR TV launched by Samsung in 2015, luminance level ranges have increased, allowing whites and blacks to be expressed more realistically. Colour ranges, too, have expanded, resulting in images that are more true to life. We call this new, broader range High Dynamic Range (HDR), while the preceding range is known as Standard Dynamic Range (SDR).

In HDR, whites and blacks are more true-to-life.

Up until now, most manufacturers and calibrators have specified and measured the range of colours that a display can reproduce in terms of colour gamut. Specifically, the American film industry has utilized the DCI-P3 colour gamut for digital movie projection.

In the world of SDR, illustrating a display’s colour gamut on a 2D colour space proved satisfactory, as calibrated displays behaved in a similar manner. Peak luminance was 100 nits and colours were generally well saturated at one luminance level, typically 75 percent of the display’s peak luminance.

But in the HDR era, things are different. Peak luminance, for example, is generally five to ten times higher, and in the case of Samsung’s QLED TVs, 15 to 20 times higher. These varying luminance levels have a big effect on how colours are displayed. As the image exceeds the display’s peak luminance, for instance, colours can be displayed differently from what they were intended to be, sometimes resulting in a wash-out effect.

Even with the same content, colours can be expressed differently on different displays, depending on their luminance range.

So, while 2D colour spaces were sufficient to indicate colour gamut in the SDR era, things are different in the world of HDR, where luminance levels differ greatly. Therefore, a new colour standard needed to be established to ensure that the HDR content that’s being produced, broadcast and displayed is correct and retains the content creator’s original intentions.

The Importance of Colour Volume

To accommodate the variations of different displays, luminance was integrated as a third dimension into the traditional 2D colour gamut diagram to create colour volume. This 3D measurement illustrates how a display reproduces colours at all of the luminance levels of its luminance range.

Unlike the conventional two-dimensional CIE 1931 color space diagram (left), three-dimensional color volume takes luminance into account, and is thus a better measure of a display’s colour rendering capacity.

Put simply, the higher the colour volume, the better display can express a vast range of vivid, accurate colours. Samsung’s QLED TVs’ ‘100 percent colour volume’ verification means that all colours of the DCI-P3 colour space can be expressed regardless of differing levels of brightness, ensuring that HDR images can be viewed in the way the content producer intended.

With 100 percent colour volume, Samsung’s QLED TVs display colors in true to life form.

Bringing together the features that define HDR for consumers such as higher contrast, greater peak luminance levels and the ability to render a wide colour gamut over a large range of luminance levels, colour volume will no doubt continue to become a growing area of interest in the display industry. The future of TV is here, and it is colourful!