The confusion is complete

Is 4K better than UHD, the same as UHD, or less than UHD?

First there was 4K – the Digital Cinema Initiatives’ format (DCI-4K). It had a resolution of 4096×2160 and an aspect ration of 17:9. Then came the new TV resolution, 3840×2160, because since the advent of HDTV, TV sets have an aspect ration of 16:9. Not incidentally, this resoluton is exactly twice the horizontal and vertical resolution of HDTVs 1920×1080. Initially, this format had been labeled ‘4K’ as well by some companies, such as Sony. The CEA however (called CTA in the meantime) officially named it ‘Ultra HD’ or UHD for short, and several standards bodies followed suit.

Many TV brands have stuck with the catchier ‘4K’ branding, often in addition to the ‘Ultra HD’ term, and most journalists use the terms interchangeably too. Some argue it’s perfectly fine to do so most of the time, and they have a point. Purists would disagree. I try to keep using the terms correctly as much as possible but will compromise now and then to fit the constraints imposed by a tweet. Of course, there are more differences than spatial resolution alone:

 

Ultra HD (UHD)

4K

Standardization body

Many (SMPTE. CTA. EBU/DVB/ITU, UHD Alliance, UHD Forum)

DCI (Digital Cinema Initiatives)

Vertical resolution

2160

2160

Horizontal resolution

3840

4096

Aspect ratio

16:9
(1.78:1)

17:9
(1.90:1)

Frame rate

24 fps
25/30 fps
50/60 fps
100/120 fps

24 fps

Color depth

8/10/12-bit

12-bit

Color space

BT.709/Rec.2020

CIE 1931 XYZ

Color subsampling

4:4:4, 4:2:2 or 4:2:0

4:4:4

So there’s a group of people advocating 4K is more than UHD (more pixels), meanwhile there’s another camp of people conflating the two, arguing the differences are negligible or irrelevant. Now to add to the confusion there’s a third camp – people who imbue the term ‘Ultra HD’ with more meaning than the above specifications, suggesting Ultra HD means “4K” resolution, plus High Dynamic Range (HDR), Wide Color Gamut (WCG) and possibly a whole bag of other goodies that some people have decided to call ‘HDR+

Of course, that would have been an interesting option if it had been defined like this from the start, about three years ago – 4K is 4K, and Ultra HD is about 4K+HDR+WCG. Unfortunately, that has not happened and we cannot turn back the clock to repeal the thousands of articles that have been written about Ultra HD, eliminate any awareness of this definition or withdraw the millions of Ultra HD TV sets that have been sold without HDR and WCG.

Repositioning Ultra HD to mean ‘4K+HDR+WCG’ is an interesting idea but it’s impossible to do. We’ll need a new name to convey this new meaning. You can’t expect to use an existing name. This consideration may have prompted the UHD Alliance to come up with the ‘Ultra HD Premium’ branding. Quite practically, this branding even comes with a set of specifications in terms of dynamic range and color gamut that products have to adhere to in order to be eligible. These specs do not quite specify everything (e.g. how parameters should be measured exactly), causing some manufacturers to reject them. Sony meanwhile chooses to label its products with its own proprietary ‘4K HDR’ branding (even though its products meet the requirements) in line with its earlier decision to stick with ‘4K’ rather than ‘Ultra HD’.

UHD Alliance's ultra HD Premium logo   Sony 4K HDR logo

Evidently, this area is prone to a lot of confusion – even some professional journalists are confused. Clearly then there’s a lot more work to be done for manufacturers and standards bodies to educate the press and the trade, who can then in turn help educate the consumer. Let’s hope these parties will have the wisdom to do so, rather than to confuse, conflate and obfuscate the terms we’ve already been given.

 

Yoeri Geutskens has worked in consumer electronics for more than 15 years. He writes about high-resolution audio and video. You can find his blog about Ultra HD and 4K at @UHD4k.

 

 
© 2016 Yoeri Geutskens. All rights reserved.