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| Screen Name |
Resolution (Pixels) |
Also Known as |
|---|---|---|
| SD | 720x576 | Standard Definition |
| qHD | 960×540 | Quarter HD (1/4th or Quater of Full HD) |
| HD | 1280×720 | 720p, 720p HD |
| Full HD | 1920×1080 | 1080p |
| Quad HD | 2560×1440 | WQHD, 1440p (Four times 720p or HD) |
| 4K Ultra HD | 3840×2160 | UHD, 4K (Four times Full HD) |
| 8K | 7680x4320 | UHD-2 (Four times 4K or 16 times Full HD) |
HD, or High Definition, refers to the detail level of a screen; or to put it another way, the number of pixels that are packed into a display. A pixel is the smallest visible element on a display, the ‘dots’ that combine to make up the overall picture.
720p, 1080i and 1080p are all versions of HD, but they’re all different. It’s important to note that you can’t actually buy a TV set with a 1080i display, for reasons which we’ll go into a bit later. So to begin with, we’ll just look at 720p and 1080p and the differences between those.
In the analogue TV days, all TVs used the standard definition of 576i. Video content came in a 720 pixels wide by 576 pixels tall resolution, also known as ‘standard definition’ or SD.
A 720p screen is 1280 pixels (wide) x 720 pixels (tall). That’s more than twice the detail of standard definition, which makes for reasonably sharp video playback on a standard TV. However, 1080p goes even further, racking up the pixel dimensions to 1920 x 1080 – that’s five times more detailed than SD.
Most 720p TV sets you’ll see in shops will be marketed as being ‘HD Ready’. This is because 720p is the absolute minimum required to meet this standard. Most 1080p sets you’ll see will be marketed as being ‘Full HD’ or ‘True HD’ as it gives you a richer, more well defined viewing experience.
Every broadcast or format your TV receives will be displayed in its native resolution. So if your 720p set receives a 1080p signal from a broadcast, Blu-ray player or games machine, it will downscale it to fit on the screen. Similarly, any standard definition 576p broadcasts will be upscaled. All HD channels from the BBC, Sky for example are broadcast in 1080i. A 720p HD TV would then downscale this resolution to fit, while a 1080p TV set would be able to handle it natively.
1080i and 1080p broadcasts both display images at the same pixel count as each other – 1920 x 1080. The big difference is in how images are made up on your TV.
The lowercase ‘i’ in 1080i stands for interlaced scan. The lowercase ‘p’ in 1080p stands for progressive scan.
Interlaced scan renders images in vertical lines, breaking down the picture into individual columns and then displaying every other line at a very high rate – at 1/25th of a second. Odd-numbered lines get painted on the screen first, then even numbered lines. While this is incredibly fast and impossible for the human eye to detect, it can create a ghostly flickering effect on live TV broadcasts, particularly live sporting events.
Progressive scan renders images sequentially, all at once. This makes for a much smoother image overall that doesn’t suffer from this ghosting effect. What’s more, flat-panel displays like LCDs, LEDs and plasmas will automatically convert any incoming 1080i signal to 1080p. Good quality TVs will use clever processing to replace the missing lines, but cheaper TVs won’t look as good.
Interlaced scan was introduced for analogue TV both as a form of data compression (only sending half the signal at any one time) and because old-school CRTs (cathode ray tube) TVs in the past couldn’t physically scan screens fast enough for a progressive picture.
Quad HD is another name for WQHD, which stands for ‘Wide Quad High Definition’. Quad HD screens have a 2,560×1,440 pixel resolution. This is four times the number of pixels you get on a standard HD panel (720p), hence the name. Quad HD screens aren’t as sharp as 4K Ultra HD displays.
WQHD displays also have a 16:9 widescreen aspect ratio, which explains where the ‘W’ in WQHD comes from. This is becoming an increasingly common aspect ratio in mobile phones, which are now often used to enjoy video on the move.
The term QHD originally stood for Quarter High Definition, which refers to any display packing a resolution of 960×540. That’s precusely one quarter of the number of pixels found in a Full HD screen (1920×1080). Older phones like the Samsung Galaxy S4 Mini have QHD screens.
Of course, QHD screens on mobile phones are thankfully fast becoming a thing of the past, as even basic budget phones now sport at least a 720p HD screen (1280×720). This makes for much sharper images.
However, you might now see some of the latest smartphones packing a ‘QHD’ screen according to their manufacturers or retailers. This will almost certainly mean the mobile in question has a Quad HD screen (2560×1440), rather than the old Quarter High Definition resolution.
QHD+ phone displays are longer than typical mobile screens, giving a widescreen appearance which is better suited to movies. The exact resolution of a QHD+ screen will depend on its aspect ratio. For instance, the LG G6 enjoys an 18:9 aspect ratio (or 2:1 to put it more simply), and a screen resolution of 2880×1440.
The G6’s QHD+ panel is just as sharp as the Note 7’s screen, which boasts a 2560×1440 Quad HD resolution and the same size of screen. The G6 just needs more pixels to accomodate that extra length.
4K, or 4K Ultra HD, refers to screens with a resolution of 3,840×2,160. This is four times as many pixels as you’ll find in a 1080p Full HD (1920×1080) panel. Here 4K refers to the number of pixels in the horizontal direction.
This is why ‘Quad HD’ is a slightly daft name – it’s too easy for people to mistake it for 4K.
A 55" 1080p TV will have the same amount of pixels as a 50" 1080p TV or a 6" inch 1080p smartphone, what's different is the size of the pixels, spacing between them and and hence the pixels per inch (ppi).
You might be thinking that smaller pixels are better, and you are right, when pixels are too big (and you are close enough) 1080p will look blurry. The larger the display (keeping the resolution same) lower is the pixel density or the ppi.