Answers.Body: <p>The problem is that definitions such as HD, UHD and 4k etc. are partly hype. Marketers for AV equipment like to be rather elastic with the truth, hence the rather rubbery definitions. They're not standards such as <a href="https://en.wikipedia.org/wiki/Broadcast_television_systems#ATSC" rel="noreferrer">ATSC</a> or DVB, or <a href="https://en.wikipedia.org/wiki/Graphics_display_resolution" rel="noreferrer">graphic display resolutions</a> such as VGA, WXGA etc., they're really just buzzwords.</p>
  
  <p>There are other complications - like the different broadcast standards for SD — so that SD PAL is 576 visible lines and SD NTSC is 480 lines — or <a href="https://en.wikipedia.org/wiki/Pixel_aspect_ratio" rel="noreferrer">non-square pixels</a> in digital video meaning that even a 16:9 HD 1080p image can be either 1440x1080 or 1920x1080*. So it's pretty understandable that you're confused.</p>
  
  <p>For what it's worth, the general consensus is that:</p>
  
  <ul>
  <li><strong>SD</strong> refers to 576i / 480i (with the unusual <a href="https://en.wikipedia.org/wiki/Enhanced-definition_television" rel="noreferrer"><strong>EDTV</strong></a> variant being 576p and 480p). Display resolution is 768 × 576 PAL or 720 × 534 NTSC, often the actual pixel resolution is reduced, as in the case of DV: 720 × 576 PAL or 720 × 480 NTSC, with non-square pixels</li>
  <li><strong>HD</strong> refers to 720p and 1080i / 1080p. The display resolution is 1280 × 720 or 1920 × 1080, but sometimes the horizontal pixel resolution is reduced, e.g. HDV which is 1440 × 1080 with non-square pixels. You could also say that resolutions higher than this are also High Definition. So in one sense it's anything that isn't standard definition. Note that there is no 720i.</li>
  <li><strong>Full HD</strong> or <strong>FHD</strong> means the 1080 flavour of HD (either interlaced or progressive)</li>
  <li><strong>2K</strong> describes the Digital Cinema Initiative resolution of 2048 × 1080, this resolution is based on the historical resolution of scanned super 35mm film. As with 4K it is a little slippery, and can sometimes be used to describe FHD. As the wikipedia article states it describes content <em>"having horizontal resolution <strong>on the order of</strong> 2,000 pixels"</em>. So in other words: near enough is good enough.</li>
  <li><strong>QHD</strong> or <strong>Quad HD</strong> - 2560 × 1440 is a whacky one, it's twice the resolution of 720p. The "quad" refers to there being four times the pixels of a 720p frame. Not to be confused with QFHD - see below.</li>
  <li><strong>UHD</strong> refers to 3840 × 2160, and like HD also sometimes to higher resolutions like <strong>4K</strong> and <strong>UHD 8K</strong></li>
  <li><strong>QFHD</strong> is 3840 x 2160 "Quad Full HD", the quad referring to the fact that it has four times the pixels of a FHD frame, which sounds better than saying it has twice the horizontal and vertical resolution. QFHD = UHD</li>
  <li><strong>UHD 4K</strong> - 3840 × 2160, is double the HD 1080 frame size, and is also sometimes called <strong>4K</strong>, even though the horizontal resolution is less than 4000 pixels. UHD 4K = UHD</li>
  <li><strong>UHD 8K</strong> or <strong>FUHD</strong> is 7680 × 4320. I'm guessing that as the FUHD sets hit the shops they'll be called "8K" by the salespeople.</li>
  <li><strong>4K</strong> usually refers to Digital Cinema Initiatives 4K which is 4096 × 2160 but the term is sometimes used to refer to <strong>UHD 4K</strong></li>
  <li>Similarly <strong>8K</strong> should properly refer to 8192 × 4320 but is also applied to <strong>FUHD</strong></li>
  </ul>
  
  <p>Note that there are cameras such as the Red cameras that shoot in-between resolutions such as 3K, 5K and 6K. But that's just for production, the finished media will usually be cropped / scaled to a more standard resolution for display or broadcast.</p>
  
  <p><strong>TL;DR</strong> If you're trying to define anything in technical terms and want to be unambiguous just give the pixel dimensions; terms like HD, UHD etc are really <a href="https://en.wikipedia.org/wiki/Fear,_uncertainty_and_doubt" rel="noreferrer">FUD</a>. They're more for marketing than anything else.</p>
  
  <p>Edit: Here's a handy chart:</p>
  
  <p><img src="https://i.sstatic.net/BBTL1.png" alt="here&#39;s a handy chart"></p>
  
  <p>pdf version available <a href="http://blob.pureandapplied.com.au/i-can-haz-all-the-resolutions/" rel="noreferrer">here</a></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-02-02T06:58:46.873Z
Answers.Text: *not to mention that the broadcast signal has hidden lines, meaning for example that an analogue PAL broadcast picture actually has 625 lines, 49 of which are blanked
Answers.UserDisplayName: stib
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-02-02T13:17:14.730Z
Answers.Text: The usual shorthand is to just count the vertical lines, with the assumption of a 16:9 aspect ratio.  (4k may change this, since it's ~19:10, and counts the horizontal.)  It's a pretty silly way to operate, because most movies are wider than 16:9, so they are 1920x880 or whatever, but still called 1080p.  IDK if counting vertical rez is a holdover from interlacing (which seriously hurts vertical resolution, thus making it an important number).  Or more likely it's a holdover from analog, where there were a specific number of vertical lines, but horizontal was fully analog.
Answers.UserDisplayName: Peter Cordes
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-02-02T13:22:15.190Z
Answers.Text: TL;DR summary: unless you're trying to sell something with buzzwords, just say what you mean.  Like 480i60, or 1080p24, or 3840x2160p30, to make up some examples.  Or optionally leave off the refresh rate and say W x H, or 1080p.
Answers.UserDisplayName: Peter Cordes
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-02-02T22:26:40.763Z
Answers.Text: @PeterCordes Counting vertical lines is a hangover from analogue. Horizontal resolution was measured in MHz, being the bandwidth of the signal.
Answers.UserDisplayName: stib
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-02-04T03:29:31.157Z
Answers.Text: OK, so they are buzzwords. 4K is not better that UHD. @PeterCordes The problem with just saying the vertical is that the aspect ratio can change, meaning the resolution could be 2K aswell. Anyway, "buzzword" pretty much answers it. Thanks!
Answers.UserDisplayName: BBking
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-02-04T03:34:10.817Z
Answers.Text: Well 4K is better than UHD if by 4k you mean DCI 4K, but often 4K is used as a synonym of UHD. As an example, the first thing that came up when I searched for *4K monitor* is this: http://amzn.to/1F411dG which is described as being both UHD and 4K in the blurb (it's just UHD, but why spoil a good pitch with facts)
Answers.UserDisplayName: stib
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-02-04T03:52:57.097Z
Answers.Text: @BBking: yeah, esp for ?x2160, it's going to be a good idea to say 3840x2160p30 or 4096x2160p30, when you care about the distinction.  Or when talking about 1920x800p24 content or something, I think it's a bit silly to call it 1080p, even though it's almost totally clear that's what you meant.
Answers.UserDisplayName: Peter Cordes
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-03-03T05:38:54.400Z
Answers.Text: re: edit.  nice chat, if you can see the bottom left corner :P.  But I think "buzzword" is better than FUD, because they're not really creating doubt about OTHER resolutions, just trumpeting themselves.  I don't think the confusion about the different buzzwords properly counts as FUD.
Answers.UserDisplayName: Peter Cordes
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-11-27T06:02:31.037Z
Answers.Text: "Display resolution is 720 × 534 NTSC" <-- this can't be right. NTSC is an analog signal format, originally meant for rendering on a CRT. Fairly sure there's no provision for a TV to interpolate extra 27 lines per field. As Wiki [says](https://en.wikipedia.org/wiki/480i), the equivalent square resolution is 640x480.
Answers.UserDisplayName: Gyan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-11-27T13:44:29.253Z
Answers.Text: I think the display resolution is referring to the resolution on a computer screen in that case. The analogue signal doesn't have a horizontal resolution per se. You're right that PAL and NTSC are analogue, but there is a lot of digital content created for analogue broadcast using the respective dimensions.
Answers.UserDisplayName: stib
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-11-28T09:10:30.390Z
Answers.Text: The most common NTSC scheme on computer displays is to set a PAR of 10/11, which is applied horizontally to get a display res of 640x480. In Photoshop, create 2 canvases of 720x480 (square). Place them side-by-side and change one to NTSC aspect. It gets squashed horizontally rather than stretched vertically.
Answers.UserDisplayName: Gyan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-11-28T09:10:40.687Z
Answers.Text: In fact, the VGA standard was set with those dimensions specifically to make it [easier](https://en.wikipedia.org/wiki/Video_Graphics_Array#Signal_timings) for TV-out usage.  The only S/W I know that insists on 720x540 for use in a NTSC-standard output is DVDLab Pro. Which software do you use that has 534 for NTSC creation?
Answers.UserDisplayName: Gyan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-11-28T11:54:24.227Z
Answers.Text: I don't work with NTSC footage at all, I'm fortunate enough to live in a PAL country. So I would have copied and pasted those numbers, probably from Wikipedia
Answers.UserDisplayName: stib
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2015-02-02T06:40:10.683Z
Answers.LastActivityDate: 2016-08-02T04:09:58.243Z
Answers.LastEditDate: 2016-08-02T04:09:58.243Z
Answers.UserDisplayName: stib
Body: <p>OK, so at first it might sound like a stupid question but I'm trying to get my head around all these definitions...</p>
  
  <p>It seems that they don't have a specific resolution, but they do at the same time. It's as they have their own resolution but also are part of a group of resolutions.</p>
  
  <p><a href="http://en.wikipedia.org/wiki/Display_resolution#Televisions">Wiki says:</a></p>
  
  <ul>
  <li><p><strong>HD</strong></p>
  
  <ul>
  <li>720i</li>
  <li>1080i</li>
  <li>1080p</li>
  </ul></li>
  <li><p><strong>UHD</strong></p>
  
  <ul>
  <li>2160p</li>
  <li>4320p</li>
  <li>8640p</li>
  </ul></li>
  </ul>
  
  <p>But generally we say that 1080i is HD and 1080p is FULLHD.</p>
  
  <p>UHD has resolution 3840 x 2160 and 4K is 4096 x 2160 but 4K is UHD. Same vertical resolution (2160) but different aspect ratio, making the horizontal slightly longer by 256 pixels. And it also includes 8K...</p>
  
  <p>Is UHD a resolution, a group of resolutions or both? If it's both, why?</p>
  
Tags: <full-hd>
Title: How is "definition" (SD, HD, UHD) actually defined?
UserDisplayName: BBking
ThreadText: # How is "definition" (SD, HD, UHD) actually defined?
  
  (Asked by: username_0 on 2015-02-02)
  
  OK, so at first it might sound like a stupid question but I'm trying to get my head around all these definitions...
  
  It seems that they don't have a specific resolution, but they do at the same time. It's as they have their own resolution but also are part of a group of resolutions.
  
  [Wiki says:](http://en.wikipedia.org/wiki/Display_resolution#Televisions)
  
  * **HD**
  
    + 720i
    + 1080i
    + 1080p
  * **UHD**
  
    + 2160p
    + 4320p
    + 8640p
  
  But generally we say that 1080i is HD and 1080p is FULLHD.
  
  UHD has resolution 3840 x 2160 and 4K is 4096 x 2160 but 4K is UHD. Same vertical resolution (2160) but different aspect ratio, making the horizontal slightly longer by 256 pixels. And it also includes 8K...
  
  Is UHD a resolution, a group of resolutions or both? If it's both, why?
  
  **Tags:** full-hd
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2015-02-02. Score: 14 | Accepted answer
  
  The problem is that definitions such as HD, UHD and 4k etc. are partly hype. Marketers for AV equipment like to be rather elastic with the truth, hence the rather rubbery definitions. They're not standards such as [ATSC](https://en.wikipedia.org/wiki/Broadcast_television_systems#ATSC) or DVB, or [graphic display resolutions](https://en.wikipedia.org/wiki/Graphics_display_resolution) such as VGA, WXGA etc., they're really just buzzwords.
  
  There are other complications - like the different broadcast standards for SD — so that SD PAL is 576 visible lines and SD NTSC is 480 lines — or [non-square pixels](https://en.wikipedia.org/wiki/Pixel_aspect_ratio) in digital video meaning that even a 16:9 HD 1080p image can be either 1440x1080 or 1920x1080\*. So it's pretty understandable that you're confused.
  
  For what it's worth, the general consensus is that:
  
  * **SD** refers to 576i / 480i (with the unusual [**EDTV**](https://en.wikipedia.org/wiki/Enhanced-definition_television) variant being 576p and 480p). Display resolution is 768 × 576 PAL or 720 × 534 NTSC, often the actual pixel resolution is reduced, as in the case of DV: 720 × 576 PAL or 720 × 480 NTSC, with non-square pixels
  * **HD** refers to 720p and 1080i / 1080p. The display resolution is 1280 × 720 or 1920 × 1080, but sometimes the horizontal pixel resolution is reduced, e.g. HDV which is 1440 × 1080 with non-square pixels. You could also say that resolutions higher than this are also High Definition. So in one sense it's anything that isn't standard definition. Note that there is no 720i.
  * **Full HD** or **FHD** means the 1080 flavour of HD (either interlaced or progressive)
  * **2K** describes the Digital Cinema Initiative resolution of 2048 × 1080, this resolution is based on the historical resolution of scanned super 35mm film. As with 4K it is a little slippery, and can sometimes be used to describe FHD. As the wikipedia article states it describes content *"having horizontal resolution **on the order of** 2,000 pixels"*. So in other words: near enough is good enough.
  * **QHD** or **Quad HD** - 2560 × 1440 is a whacky one, it's twice the resolution of 720p. The "quad" refers to there being four times the pixels of a 720p frame. Not to be confused with QFHD - see below.
  * **UHD** refers to 3840 × 2160, and like HD also sometimes to higher resolutions like **4K** and **UHD 8K**
  * **QFHD** is 3840 x 2160 "Quad Full HD", the quad referring to the fact that it has four times the pixels of a FHD frame, which sounds better than saying it has twice the horizontal and vertical resolution. QFHD = UHD
  * **UHD 4K** - 3840 × 2160, is double the HD 1080 frame size, and is also sometimes called **4K**, even though the horizontal resolution is less than 4000 pixels. UHD 4K = UHD
  * **UHD 8K** or **FUHD** is 7680 × 4320. I'm guessing that as the FUHD sets hit the shops they'll be called "8K" by the salespeople.
  * **4K** usually refers to Digital Cinema Initiatives 4K which is 4096 × 2160 but the term is sometimes used to refer to **UHD 4K**
  * Similarly **8K** should properly refer to 8192 × 4320 but is also applied to **FUHD**
  
  Note that there are cameras such as the Red cameras that shoot in-between resolutions such as 3K, 5K and 6K. But that's just for production, the finished media will usually be cropped / scaled to a more standard resolution for display or broadcast.
  
  **TL;DR** If you're trying to define anything in technical terms and want to be unambiguous just give the pixel dimensions; terms like HD, UHD etc are really [FUD](https://en.wikipedia.org/wiki/Fear,_uncertainty_and_doubt). They're more for marketing than anything else.
  
  Edit: Here's a handy chart:
  
  ![here's a handy chart](https://i.sstatic.net/BBTL1.png)
  
  pdf version available [here](http://blob.pureandapplied.com.au/i-can-haz-all-the-resolutions/)
  
  > **Comments:**
  > **username_1**: *not to mention that the broadcast signal has hidden lines, meaning for example that an analogue PAL broadcast picture actually has 625 lines, 49 of which are blanked  
  > **username_2**: The usual shorthand is to just count the vertical lines, with the assumption of a 16:9 aspect ratio.  (4k may change this, since it's ~19:10, and counts the horizontal.)  It's a pretty silly way to operate, because most movies are wider than 16:9, so they are 1920x880 or whatever, but still called 1080p.  IDK if counting vertical rez is a holdover from interlacing (which seriously hurts vertical resolution, thus making it an important number).  Or more likely it's a holdover from analog, where there were a specific number of vertical lines, but horizontal was fully analog.  
  > **username_2**: TL;DR summary: unless you're trying to sell something with buzzwords, just say what you mean.  Like 480i60, or 1080p24, or 3840x2160p30, to make up some examples.  Or optionally leave off the refresh rate and say W x H, or 1080p.  
  > **username_1**: @username_2 Counting vertical lines is a hangover from analogue. Horizontal resolution was measured in MHz, being the bandwidth of the signal.  
  > **username_0**: OK, so they are buzzwords. 4K is not better that UHD. @username_2 The problem with just saying the vertical is that the aspect ratio can change, meaning the resolution could be 2K aswell. Anyway, "buzzword" pretty much answers it. Thanks!  
  > **username_1**: Well 4K is better than UHD if by 4k you mean DCI 4K, but often 4K is used as a synonym of UHD. As an example, the first thing that came up when I searched for *4K monitor* is this: http://amzn.to/1F411dG which is described as being both UHD and 4K in the blurb (it's just UHD, but why spoil a good pitch with facts)  
  > **username_2**: @username_0: yeah, esp for ?x2160, it's going to be a good idea to say 3840x2160p30 or 4096x2160p30, when you care about the distinction.  Or when talking about 1920x800p24 content or something, I think it's a bit silly to call it 1080p, even though it's almost totally clear that's what you meant.  
  > **username_2**: re: edit.  nice chat, if you can see the bottom left corner :P.  But I think "buzzword" is better than FUD, because they're not really creating doubt about OTHER resolutions, just trumpeting themselves.  I don't think the confusion about the different buzzwords properly counts as FUD.  
  > **username_3**: "Display resolution is 720 × 534 NTSC" <-- this can't be right. NTSC is an analog signal format, originally meant for rendering on a CRT. Fairly sure there's no provision for a TV to interpolate extra 27 lines per field. As Wiki [says](https://en.wikipedia.org/wiki/480i), the equivalent square resolution is 640x480.  
  > **username_1**: I think the display resolution is referring to the resolution on a computer screen in that case. The analogue signal doesn't have a horizontal resolution per se. You're right that PAL and NTSC are analogue, but there is a lot of digital content created for analogue broadcast using the respective dimensions.  
  > **username_3**: The most common NTSC scheme on computer displays is to set a PAR of 10/11, which is applied horizontally to get a display res of 640x480. In Photoshop, create 2 canvases of 720x480 (square). Place them side-by-side and change one to NTSC aspect. It gets squashed horizontally rather than stretched vertically.  
  > **username_3**: In fact, the VGA standard was set with those dimensions specifically to make it [easier](https://en.wikipedia.org/wiki/Video_Graphics_Array#Signal_timings) for TV-out usage.  The only S/W I know that insists on 720x540 for use in a NTSC-standard output is DVDLab Pro. Which software do you use that has 534 for NTSC creation?  
  > **username_1**: I don't work with NTSC footage at all, I'm fortunate enough to live in a PAL country. So I would have copied and pasted those numbers, probably from Wikipedia  
  
  ---
  
  