The difference between 720p, 1080i, 1080p, 4K and Ultra HD HDTV resolutions

Here’s a topic of confusion for many. What is the difference between the HDTV resolutions? Will I actually be able to see a difference if I update my TV? Why can’t I see the difference between 1080p and 4K?

Let me begin this by explaining a how a digital TV picture is made up. The TV screen is made up of pixels. These are a tiny squares within the TV picture that illuminate in different colour and brightness. The more pixels that are in the TV screen the better the resolution and the better the TV picture. Pixels will build the picture up and across.

So what is the difference between 720p, 1080i, 1080p, 4K and Ultra HD?

Before I go any further I will just explain the difference between the “I” and the “p” and the number bit on some of the HD TV resolutions.

Number 720, 1080 etc - This refers to the vertical resolution, so a 720p picture will be made up of 720 rows of horizontal pixels a

P – Stands for Progressive scan. The will scan and display the TV picture from the top horizontal line from left the right and then move onto the line beneath which then scans across, onto the next line and so on.

I – Stands for Interlaced scan. An interlaced scan like the progressive scan will scan the first top line from left to right, but then it will only scan the odd lines from there 3,5,7 etc. Once it reaches the bottom it will then scan the even numbers 2, 4, 6. Once it has completed the even numbers it will go back to the odd numbers and so on. This happens so quick that you can’t see it but it does leave some traces, namely why you never see newsreaders wearing striped shirts and the interlacing pictures don’t always lap perfectly leaving it looking almost blurry, but having said that ‘de-interlacing’ techniques can be used to overcome this. The reason why an interlaced signal may be preferred over a progressive scan as this dramatically reduces the bandwidth and information required to make up the TV pictures making it perfect for broadcasts where bandwidth is limited.

What is 720p?

I remember when HD TV came out and the 720p resolution looked unbelievable, I had never seen a TV picture so clear, compared to the analogue transmissions that were around, even Sky was still using the SCART connection so that didn’t look much better. Scroll on some 20 years and now it doesn’t look great at all. A lot of 720p TV’s are also branded “HD ready”.

720p is a progressive scanned picture comprised of 720 horizontal lines of pixels and 1280 vertical lines.

What is 1080i?

A 1080i resolution is an interlaced scan with 1080 horizontal lines of pixels and 1920 vertical lines. This gives in increased picture quality to 720p but many say due to the interlacing in the frames that the picture doesn’t flow as nicely and many opt for 720p picture resolution instead, personally I would choose 1080i over the two given such as choice.

What is 1080p?

1080p also known as ‘Full HD’ is a progressive scan comprised of 1080 horizontal lines of pixels and 1920 vertical lines. As the picture is progressively scanned there are no reductions in picture quality due to the interlacing of picture frames and it offer a far greater picture clarity than that of 720p.

What is 4K, Ultra HD and UHD?

Although 4K has been around for some time it hasn’t been a financially viable product for most until recently which has seen it take off massively in the last couple of years with SkyQ, Netflix and BT Vision now offering 4K content together with affordable 4K enabled Blu-ray players. 4K also known as Ultra-HD or UHD (there is actually a difference!) depending on the TV manufacturer. However to majority of the

4K is made up of 2,160 horizontal lines of pixels and 4,096 vertical lines – hence the 4K bit. 4K is an anomaly compared to the previous resolutions as it actually quotes the horizontal resolution rather than the vertical resolution, this is a marketing at its finest as when compared to the previous resolutions it would be known 2160p which doesn’t sound anywhere near as extravagant.

UHD technically speaking is actually a picture made up of 3,840 horizontal lines and 2,160 vertical lines, 3,840 x 2,160. Although it’s almost the same it still isn’t quite but this doesn’t stop many manufacturers badging their TV’s up as 4K!

4K is actually capable of some quite remarkable pictures. It is said that of our current sized TV’s the human eye cannot actually see much clearer, so I suspect that instead of us all upgrading to 100 inch screens the majority of technological improves will be made via increasing pictures frames per second (fps) and a broader colour range.

The other downside of 4K is the bandwidth required, HDMI leads may needed to be upgraded a spec. HDMI distribution systems may no longer be up to the job and traditional means of delivery such as through terrestrial TV and via the internet may also struggle.

Items for consideration

The TV

Probably one of the biggest issues I came across is when someone has re-connected the TV from a SCART lead to a HDMI cable for HD, the say “I can’t see much of a difference” This is usually 100% down to the TV and replacing the TV for a newer model will usually bring noticeable improvements.

Size of the TV

I’m sure that most of you have already thought. If the TV is made up of tiny square called pixels then surely a smaller TV will mean that the pixels are even smaller. Yes you are absolutely right, if you have a TV beneath 32” and want to upgrade the picture quality without increasing the size I you are not likely to see a huge difference between 720p and 1080p or even 4K for that matter. If you are thinking about going to 4K then personally I wouldn’t bother with anything below 40”, but that’s just me.

Frames per second

The more frames per second (fps) the TV is capable of the smoother the transitions of TV frames will TV will appear. Simply changing to a TV with a higher frame rate can give a far more pleasurable experience. Traditional because of the technology involved Plasma TV’s had a distinct advantage over LCD models. But the new LED and OLED TV’s are more than capable of keeping up in this field and then some!

Colour Range

Not all TV’s have the same colour range. Picking a TV with a broader colour range can also create the illusion of more pixels or a higher resolution. In reality it’s just a smoother, more graceful changing of colour.

Broadcast medium

Whether your TV is broadcast via a terrestrial aerial, satellite, through the internet of via a disc will have a distinct on the TV picture quality. I won’t go too much into this as this could be a whole another blog.

Disc - Typically a Blu-ray disc will outperform the others as its only limited to the disc size and they are not going to sell you a disc that can’t contain the amount of information required. The pictures of TV’s on shops are usually supplied by a disc.

Internet / On Demand - Next internet would be the next best option, if you can download the whole file required then this would not be dis-similar to that of a disc, issues may arise when you have s slow broadband speed and it takes forever to download or buffering or reduced signal quality when streaming. This is certainly the case for Netflix and things like iPlayer and Youtube.

Aerial and satellite – Because of the bandwidth available and the modulation techniques satellite would have an advantage over terrestrial signals via a TV aerial. You would compromise as both use compression techniques to get all that extra information in which can compromise of picture quality. You may even clearly notice this in fact changing pictures such as when as when a footballer scores and the camera shoots to the crowds, with all the moving people and different colours often there is not enough bandwidth to supply this information so for a short period of time the picture can be noticeably worse.