Everything you need to know about 4K TV color: HDR, WCG and 10-bit color
Stephan Jukic – October 17, 2016
Like their resolution, backlighting technology and their smart TV features, color in today’s 4K TVs has also become more sophisticated and as a result more complicated for consumers to understand. The main reasons for this are the different color standards you’ll see thrown around about 4K TV color and which TVs come with what and thrown into this mix is all sorts of possibly mysterious technical jargon such as 10-bits, 8-bits, HDR color, quantum dots, phosphor coloring and so on.
Obviously enough, the mix of all these things can get downright confusing even for 4K TV buffs, let alone for consumers who just want a great 4K TV without saturating themselves with all sorts of details.
However, if you are one of these 4K TV buyers who wants that great TV, it is a good idea to know at least the most important stuff about how color works and which TVs deliver it at its absolute best. That’s what we’re going to tell you here with as much clarity and simplicity as possible. Here are the most important things you should know about 4K TV color today.
What exactly do you mean by 4K TV color?
You see, 4K TVs don’t all come with the same color coverage or even color technology across the board. There are older color standards for older ultra HD Televisions, which are basically the same as those found in most HDTVs and newer standards which are found in the latest and best 4K TVs with high dynamic range.
The older color standards also cover contrast levels, black performance and brightness and the TVs which can only display these are called SDR 4K TVs, just as the vast majority if not all models of non-4K UHD televisions can be considered SDR TVs.
4K TV color in these older TVs with only SDR display capacity was of a weaker sort with more limited color space coverage and color depth and this is something which 4K TV manufacturers and 4K content creators sought to change by developing what is now called HDR color display and standards, which are made up mainly by the standards of wide color gamut (WCG) and 10-bit color (as opposed to the 8-bit color of SDR content and TVs). This enhanced 4K TV color is what we’re mainly talking about here and it’s what offers the absolute best in today’s 4K TV display technology.
If you want the best possible 4K TV with the most future-proof display performance for the next generation of HDR 4K content, an enhanced color 4K TV is what you need to get your hands on. We also cover these in much greater detail throughout our guide to high dynamic range (HDR), found here.
Now you know what we’re going to discuss when we refer to 4K TV color but you’re probably still confused about what all the jargon in the previous paragraphs means. After all, what is wide color gamut, 10-bit color, SDR, HDR and so on? These things are what we’re going to cover now, one by one.
What is SDR color?
As we said, SDR color represents what you’ll find in today’s HDTVs and in many of the older 4K TVs still sold on the market (mainly from early 2015 and 2014 or before) But what exactly is it? Quite simply, it is digital TV color without the latest enhancements such as wide color gamut and 10-bit color depth. No 4K TV with SDR (standard dynamic range) color specs can display 4K HDR content and no such 4K TV can offer the full depth of enhanced color that has been mastered into the latest and best sources of 4K UHD HDR content.
A 4K TV with SDR color can only display a total of 16.7 million colors because it offers only 8-bit color depth and only display a limited part of the whole visible color spectrum because it doesn’t offer wide color gamut according to the best 4K TV display standards available today for high dynamic range in particular. The current benchmark for these wide color standards is called DCI-P3 (Digital Cinema Initiative-P3) and SDR TVs without WCG can display no more than maybe 80% of this color space. HDR 4K TVs with Wide Color Gamut can on the other hand display more than 90% of the same color spectrum space.
What is HDR color?
HDR color is found only in the most modern and generally best 4K TVs released in mid to late 2015 and in all of 2016. It is increasingly found in a growing percentage of all 4K TVs released by each of the major television makers today and it is what covers the essence of “enhanced” color as you the consumer need to understand it.
Full enhanced HDR color basically consists of wide color gamut and 10-bit color as we described them above and it’s found in all the flagship 4K TVs of late 2015 and all of 2016 and also found in many of the mid-range and even budget 4K TVs for 2016 in particular. Most 4K TVs will come with full HDR color by 2017 as far as we can predict and this is a wonderful thing to behold because the color enhancements delivered by wide color gamut and 10-bit color are huge when compared to what you’d see with regular SDR display and 8-bit color.
What about HDR color and HDR Contrast?
On the other hand, not all HDR 4K TVs come with HDR color. You see, as we cover much more fully in our HDR standards guide, high dynamic range is about both color enhancements and greater range of contrast steps between enhanced dark levels and enhanced levels of peak brightness. Thus, a 4K TV with HDR can have either both or just one of these pillars of high dynamic range. Some 4K TVs can come with HDR contrast enhancements but lack HDR color enhancements and other 4K TVs can come with exceptional HDR color performance but lack certain aspects of HDR contrast performance.
The best possible color performance in a 4K TV will however come from HDR TVs which offer both enhanced color and exceptionally high levels of peak brightness, deep local dimming and black performance. This is because brightness, black performance, local dimming and contrast range are integral to making the colors they work around stand out more vibrantly and realistically. Our guide to 4K TV backlighting goes into a lot of detail about how backlight technology in 4K TVs enhances overall picture quality.
What does 10-bit color mean?
Now to define just what the 10-bit color we’ve been referring to all this time means. Quite simply, it defines the range of possible color values per RGB subpixel in each pixel of a 4K TV display. All 4K TVs create their entire range of colors through the use of Red, Green or Blue (RGB) sub-pixels inside each individual pixel on their screen. White is created by activating all three sub-pixels at the same time in a certain way though with some 4K TVs there is also a pure white sub-pixel and in a rare few 4K TVs there are also yellow sub-pixels. For the sake of simplicity however, the vast majority of 4K TVs come only with the three RGB sub-pixels per full pixel. Each of their subpixels can either be 8-bit or 10-bit. In an 8-bit pixel, the colors it represents (red, green and blue) can be varied to 256 different shades each. In a 10-bit TV display, each sub-pixel can on the modified to 1024 different tones of teach RGB color (again, either red, green or blue).
Now, to really see just how much impact these two extra bits offer in a 10-bit HDR 4K TV color display, we need to multiply all the primary color mixes possible by each other. Thus, for an 8-bit 4K TV, you get 256 x 256 x 256, amounting to a total of 16.8 million colors and in a 10-bit TV, you get 1024 x 1024 x 1024, amounting to 1.07 billion color possibilities per pixel.
This is why a 10-bit TV panel or a 4K TV panel which simulates 10-bit display effectively (as most panels actually do without truly offering 10-bit color depth) can create a far richer, smoother quality of color for 10-bit HDR content. The effect created is one of much better realism and much better color accuracy if you’re using an HDR TV to watch content mastered with 10-bit color depth.
What does Wide Color Gamut mean?
Wide color gamut, or WCG, is a bit of different thing from 10-bit color depth. It represents all the possible colors of a color gamut that a 4K TV can display. Thus, a 4K TV with HDR color can show a much larger area of the total visible color spectrum than a SDR TV without enhanced color.
The specific color gamuts most often used to denote what means wide color gamut and what means narrow color are Rec.709, DCI-P3 and Rec.2020. The Rec.709 color space is what was used for years and still is used as the maximum color coverage of HDTVs and most SDR broadcast and other digital media content. However, Rec.709 is only a smaller part of the bigger DCI-P3 color space, which is itself a smaller part of the newest digital enhanced color broadcast space known as Rec.2020. No TV in existence today shows full Rec.2020 coverage but all HDR 4K TVs with enhanced color show at least 90% of the DCI-P3 color space and more than 100% of the Rec.709 color space. A 4K TV which shows 90% or more of DCI-P3 color is however only showing something around 60% of the Rec.2020 color spectrum.
The bottom line for wide color gamut is that it’s a key part of HDR color in a 4K TV and that this technology is what will let the television you buy fully display the wide spectrum of colors which have been mastered into the high dynamic range content that’s available from sources like 4K Blu-ray, Netflix, Amazon Prime and other streaming content providers.
So where does HDR and SDR content fit into the picture (literally)?
HDR color through WCG and 10-bit color depth only apply in your 4K TV when it comes to watching content with HDR color support (WCG and 10-bit color) mastered into it during production. Today’s 4K HDR TVs with enhanced color won’t use their full color enhancement capacities if they’re displaying the vast majority of content which is still 8-bit and SDR in its color gamut coverage.
This is unfortunate but it is at least changing as more HDR content gets produced in 4K resolution for the growing percentage of HDR 4K TVs. Also, TV makers themselves are working on new upscaling technologies for the best 4K TVs sold today so that they not only upscale non-4K video to look sharper and more ultra HD-like (as all 4K TVs of both the HDR and SDR type already do), but also upscaled SDR video from broadcast, disc and streaming sources to benefit from some of the built-in 10-bit and WCG color capacities of these 4K TVs. Two notable examples of premium 4K TVs which are doing this include Sony’s latest Z9D HDR models, Samsung’s 2016 SUHD TVs and LG’s 2016 OLED HDR televisions like the G6, E6 and C6 4K TV.
This HDR-upscaling effect is still far from perfect but it is working to at least partly improve the quality of content with SDR color formatting as it renders on a 4K HDR TV display.
However, for now, the absolute best entertainment you can get if you want your TV to really show off its enhanced HDR color capacity is native HDR 4K video from a 4K Blu-ray disc or Netflix and Amazon’s selections of streamed HDR programming.
What about Quantum dots, phosphor coatings and all those other buzzwords?
If you’re looking to buy a 4K TV with high quality enhanced color, you’ll also hear a lot about the presumed benefits of technologies like quantum dot color and color enhancing phosphors in premium 4K TVs from Samsung, LG (quantum dots) and Sony (Triluminos Display, which means colored phosphors on TV backlight LEDs).
All of these technologies are basically additional means by which TV manufacturers make their 4K HDR TVs display wide color gamut and 10-bit color even more effectively and precisely. A 4K TV with enhanced color doesn’t need quantum dots of Triluminos Display to offer wide color gamut and 10-bit color but these types of technologies allow the TV to offer even better color saturation and color tone variation than would be possible without them.
Quantum Dot Materials for a Samsung QD TV and Triluminos Display for Sony 4K televisions
What about future-proofing my 4K TV for upcoming color standards?
Most of the 4K HDR content that already exists has already been mastered to display wide color gamut and color depth which far exceed what even the best 4K TVs of 2016 can actually offer. In this one way, what little HDR content that exists is already far ahead of the much more commonly seen technology of HDR color 4K TV display in its specs.
Thus, while even the best 4K TVs of 2016 can only manage 10-bit color depth and 96% DCI-P3 color space coverage for WCG, HDR 4K video formatted for the Dolby Vision HDR standard is already capable of displaying at 12-bits and better than 100% DCI-P3 wide color gamut coverage, if it were only to be played in a 4K TV capable of showing these sorts of visuals. The growing percentage of HDR entertainment content that gets created will come with the same capabilities. What this means is that the most future-proof 4K TVs today for the most advanced content sources which already exist are those with full HDR color which includes 10-bit color depth and WCG, as well as full HDR contrast specs.
On the other hand, the vast majority of broadcast, hard disc and even streaming digital video content isn’t HDR at all and is in fact formatted to only display in 8-bit color. Thus even today’s 4K TVs are capable of more than most content can render on a screen. In other words, while you should absolutely get a 4K TV with Full HDR color, don’t worry about it being obsolete any time soon as far as the vast majority of your TV watching is concerned.
Okay so what is the bottom line?
The bottom line is this. 4K TV color can be of the more narrow SDR kind described above or it can be of the HDR color type that’s increasingly being formatted into the latest digital video entertainment. If you can get your hands on a 4K TV with full HDR, then do so, because it will offer you the best quality for the latest color and contrast mastering in today’s most recent HDR movies and TV shows. However, don’t obsess too much about color beyond this either since home entertainment video itself still has plenty of catching up to do before most of it is 10-bit or WCG-capable.
Story by 4k.com