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Comment by jtokoph | Hacker News Reader

Does it bother anyone else that we've moved from describing displays by vertical resolution (1080/720) to horizontal resolution (4K)?

It seems confusing for the semi-informed.

Is there an explanation other than marketing reasons?

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It's the difference between the movie industry and TV industry.

TV has always described resolution in "lines", because only the vertical direction had a fixed number of lines, the horizontal was analog and thus there wasn't a specific number of lines (there was a maximum frequency it could display accurately, and thus a minimum feature size, but no discrete "lines"). So, SD NTSC is 480i (i for interlaced), PAL is 576i. Actually, NTSC was really 525 lines, but some of them were not visible and part of the blanking interval. When you started moving into HD, they kept this convention, referring to 720p, 1080i, 1080p, etc.

When movies started being distributed in digital formats, the movie industry chose a different standard of naming the resolutions, calling it 2K for 2048x1080. I'm not sure why they chose to focus on the horizontal rather than vertical resolution like the TV industry, but there you go. So the 2K/4K terminology comes from the movie industry, 720/1080 from TV.

Just be glad that we're using this term and not the computer industry term for it, which is WQUXGA (edit: sorry, QFHD, WQUXGA has 2400 vertical pixels, not 2160, see how memorable these names are?), though it is frustrating that "4K" is used for something that doesn't actually have over 4000 pixels in either dimension. In fact, this doesn't meet the official definition of 4K, it's actually just 4 times the size of 1080p, so it would be more appropriate to name it 2160p or QFHD instead of 4K. But for some reason, 4K has become the de-facto buzzword for this generation of resolutions, so it's what we're stuck with.

I wonder if the film industry refers to horizontal resolution because they've historically referred to film by the horizontal dimension of the film: a 35 mm film strip is 35 mm wide, 8 mm is 8 mm wide, etc.

Admittedly, those are the widths of the film strips rather than the frames, so there is no direct correspondence here, and there are formats (such as IMAX) which run the strips horizontally, so the width of the strip constrains the height of the frame, rather than its width. But this is my story and i am sticking to it.

Ah, that's a good point. On film, the horizontal size is the constraining factor, and they can choose how much vertical real estate to use per frame to give the aspect ratio they would prefer.

It's confusing, because 4k has been used as a term (not actually that often in practice) in the VFX industry for 5/6 years for the following resolutions:

4096 × 2160 (standard) 4096 x 3112 (super 35)

Then for 4k cameras, the following resolutions have become fairly common for "4k":

3840 x 2160 4096 x 2304

so these days, it's difficult to know what's been talking about...

What's even more confusing is that after we've settled that 3840x2160 is 4k, which is 4x the pixels of 1920x1080, just like 8k is 4x the pixels of 4k, instead of calling 1920x1080 "2k", everyone is starting to call 2560x1440 "2k", even though 4k is only ~2x the pixels of 2560x1440.

I actually prefer UHD being promoted, because I wouldn't want us to switch to another weird resolution now, and I want videos to just scale up perfectly.

Actually, I've seen 2560x1440 called "2.5K" (at least Blackmagic calls it that in their Cinema Camera which shoots 2432 x 1366), since 2K has a well established definition of 2048x1080, or some crop of that to meet a desired aspect ratio. In film, 4K is defined as 4096x2160, which is exactly 4 times the number of pixels as 2K.

Marketing is a huge reason. "HD" laptop screens, for example, were meaningless but attached a moniker that the average consumer was familiar with ("HDTV") to a platform they are less knowledgeable about (laptops). I think the whole HD/720/1080 marketing push created stagnation within the display industry, since there was little reason to build better displays beyond 720/1080.

I am hopeful that with Retina and 4K, we'll swing back into a push for progressively better & progressively cheaper displays -- much like we had with the initial LCDs when they first started coming onto the market.

It bothers me.

But (just a guess) I hypothesize 4K comes from the film industry, while 720p and 1080[ip] come from TV and computer industries. So the two systems of measuring resolution were created independently and both have historical precedents, and the marketing mishap stems from blithely conflating the two. So I guess my explanation is: coincidence

Yes. Representing resolution by horizontal pixel count has been standard in digital cinema for years[1][2]. So they have 2k, 4k and a number of subvariants.

So I guess we're just seeing a conflation of cinema, TV and computing, at least when it comes to displays and resolutions, so the marketing terminology is conflating too.

Especially since 4k is an exisiting standard, I'm willing to give them a pass for keeping the naming convention. (Although the 4k TV standard, which most 4k monitors will be using, is slightly different: It's the cinema standard cropped to a 16:9 aspect ratio.)

[1] http://en.wikipedia.org/wiki/Digital_cinema

[2] http://en.wikipedia.org/wiki/Digital_Cinema_Initiatives#Imag...

Dell might agree. 4K does not appear anywhere on that webpage.

AFAICS it doesn't meet all aspects of the TV world's 4K spec, specifically the new colour regime. (99% of https://en.wikipedia.org/wiki/Adobe_RGB_color_space has to be a smaller colour space than https://en.wikipedia.org/wiki/Rec._2020 surely.)

The article you linked on Rec. 2020 says:

> In coverage of the CIE 1931 color space the Rec. 2020 color space covers 75.8%, the digital cinema reference projector color space covers 53.6%, the Adobe RGB color space covers 52.1%, and the Rec. 709 color space covers 35.9%.

So yes, Adobe RGB covers less of the reference color space than Rec. 2020 (4k/UHD), but more than Rec. 709 (HDTV).

No display of any kind meets the Rec. 2020 gamut spec. It's more a future proofing step than a realistic target. The fact that the primaries are sat right on the single-wavelength line indicates an eye towards future laser projectors though - the gory details of how the decisions were made start at page 27 of http://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-BT.2246-2-201...

Well they do mention it indirectly

Ultra HD 3840 x 2160 packs in four times the resolution of Full HD

4K means ~4000 pixels wide, not "four times HD".

Full HD has a defined pixel size, and they're simply saying that this screen has twice the resolution in both directions.

Ultra High Definition or UHD includes 4K UHD and 8K UHD.

4K UHD is 2160p which is 3840 pixels wide by 2160 pixels tall, which turns out to be four times as many pixels as 1920 × 1080

which is quite a long way from actually using the term "4K"

Anyone trying to sell monitors won't use the term 4K.

Dell is smart and won't ever use 4K while selling monitors, thats why they said four times HD instead of 4K.

Which makes sense because 4K resolution exist in the field of digital cinema, digital cinematography and digital television.

So far the only explanation I've seen is the number of syllables. "Ten-eighty pee" and "seven-twenty pee" are relatively easy to say on the radio, TV, and sales floor, but "twenty-one-sixty pee" starts to get unwieldy. Note that 2K (i.e. 1080p) has been used as a definition in the past [1], just very rarely, so it really is just the marketing of it that's changing.

[1] https://en.wikipedia.org/w/index.php?title=2K_resolution&act...

I have no idea.

I would prefer "2X", which Apple calls retina. We could also call it 4X with respect to area, but 2X would be the scaling factor for applications to hit.

I find it kind of annoying we still use diagonal dimension to describe the size, particularly when the monitors come in different aspect ratios.

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