What is 4K Ultra HD?

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by Tony O'Brien

20th February, 2014

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What is 4K Ultra HD?

It’s been hard not to notice all of the attention that 4K Ultra HD has been getting recently. But what does the new format offer, is it the next big step in TV technology, or is it just a gimmick? This article will tell you about 4K Ultra HD and what you can expect from it.

Diagram 1: 4K Ultra HD Resolution
Diagram 1: 4K Ultra HD Resolution

4K Ultra HD is a new format, which offers both greater resolution and a far greater range of colours than has ever been possible from any video format before. Boasting a resolution of 3840 x 2160* pixels, it provides 4 times the resolution of Blu-ray, and much greater resolution than DVD. Diagram 1 shows the relative pixel size of these different formats. If you haven’t seen an in store demonstration of 4K Ultra HD, I strongly urge you to take a look, much like the improvement from DVD to Blu-ray the difference provided by the extra resolution really has to be seen!

Much of the attention has focussed on the increased resolution of 4K Ultra HD, however the format is also capable of producing a huge range of colours. Diagram 2 illustrates the CIE 1931 colour space (the large horseshoe of colour) and the Rec. 709 colour standard (the smaller triangle of colour). Material which has been mastered in the Rec. 709 standard (which includes Blu-ray) is capable of achieving all of the different variations of colour shown within the triangle. The CIE 1931 colour space shows the visible spectrum of colour which is much larger than the Rec. 709 standard. This means that when we’re watching a Blu-ray we’re seeing less than half of the range of colours which are visible to the human eye.

Diagram 2 Blu-ray Colour Space (Rec. 709)
Diagram 2: Blu-ray Colour Space (Rec. 709)

Diagram 3 illustrates the CIE 1931 colour space and the Rec. 2020 colour standard which the International Telecommunications Union (ITU) **  have proposed  for 4K Ultra HD. Comparing the Rec. 2020 triangle, with the Rec. 709 triangle in Diagram 2 shows how much more of the visible range of colour is obtainable with the new colour standard. This means that if this new colour standard comes to fruition, we will see a considerably greater range of colours than we have ever seen before from any video medium. In fact, with this new colour standard, your next TV could outclass the level of colour performance at your local cinema!

Diagram 3 4K Ultra HD Colour Space (Rec.2020)
Diagram 3: 4K Ultra HD Colour Space (Rec.2020)

The challenge at this point is realising the full potential of the new format. There is currently no physical media (discs) available for 4K Ultra HD and online content is rare. While a new disc format for 4K Ultra HD is being developed, there have been no announcements on its availability as yet. Furthermore, it’s unlikely that current 4K Ultra HD TV’s are capable of producing the wide range of colours necessary to produce the Rec. 2020 format. So even if the new disc format does adopt the Rec. 2020 standard, further advances are needed in display technology in order to represent the full potential of the format.

This means the bulk of your viewing is likely to be Blu-ray which has been upscaled (either by your Blu-ray player or TV) from 1920 x 1080, to 3840 X 2160. If you have ever watched DVD’s on your HDTV (which are automatically upscaled to 1080p by either your Blu-ray player or TV), you would have noticed that while upscaled DVD is an improvement over regular DVD, it’s still no match for actual Blu-ray movies in 1080p. Much the same is going to hold true when watching Blu-ray on a 4K Ultra HD TV.

While today’s incarnation of the technology does bring some improvement to Blu-ray playback, when actual content arrives we are going to see a large stride forward in terms of resolution. Couple this with TV’s (and physical media) that are capable of producing the full Rec. 2020 colour gamut and we have a technology which will truly outclass anything we have seen in our homes before.

* You may have noticed that the title of 4K is not correct, given it has a horizontal resolution of 3840 pixels and not 4000 pixels. The reason that the slightly lower pixel count has been adopted is because it provides an exact multiplier over Blu-ray (4x). This solves some compatibility issues between the two formats.

** The International Telecommunications Union (often referred to as the ITU), is responsible for developing the technical standards for communication technologies. While the new Rec. 2020 has been recommended for 4K Ultra HD by the ITU, a standard for the 4K Ultra HD disc format (including colour standard) has yet to be formalised by the Blu-ray Disc Association (referred to as the BDA) .

Resources:
Joe Kane (2013), Science of Imaging: Update On 2160p, Widescreen Review Issue 173
Joe Kane (2013), Science of Imaging: 2160p Continued… Widescreen Review Issue 174
Joe Kane (2013), Science of Imaging: Could 2160p Usher In A New TV System? Widescreen Review Issue 177
Joe Kane (2013), Science of Imaging: What Color Is It? Widescreen Review Issue 178
Joe Kane (2013), Science of Imaging: More Details About 2160p, Widescreen Review Issue 179
ITU Press Office Press Release, Ultra High Definition Television: Threshold of a new age, ITU  Recommendations on UHDTV standards agreed, May 2012. Accessed 20 February 2014. http://www.itu.int/net/pressoffice/press_releases/2012/31.aspx#.UwKthPmSw9c
ITU, Recommendation ITU-R BT. 2020 (08/2012) Parameter Values for Ultra High Definition television systems for production and international program exchange. Accessed 20 February 2014.
http://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.2020-0-201208-I!!PDF-E.pdf

Sakurambo, derivative work: GrandDrake (talk) File:CIExy1931 Rec 2020.svg Wikipedia (1 October 2012) Accessed 20 February 2014.
http://en.wikipedia.org/wiki/File:CIExy1931_Rec_2020.svg
Sakurambo, derivative work: GrandDrake (talk) File:CIExy1931 Rec 709.svg
Wikipedia (1 October 2012) Accessed 20 February 2014.
http://en.wikipedia.org/wiki/File:CIExy1931_Rec_2020.svg


About the Author

Tony O'Brien is the owner of Adelaide based 'Clarity Audio & Video Calibration', providing calibration services to home theatre owners and video production companies for film and TV. He is an ISF Certified calibrator.
For more information visit http://www.claritycalibration.com.au

Posted in: Visual & Home Cinema Technology & Smart Homes
Tags: 4k  ultra hd 

Tony O'Brien's avatar

Written by:

Tony O'Brien

As the owner of Adelaide based 'Clarity Audio & Video Calibration', Tony is a certified ISF Calibrator. Tony is an accomplished Audio-Visual reviewer specialising in theatre and visual products.

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