The TV aspect ratio is a term we often hear in relation to our televisions.
People talk about "widescreen TV" and "4 by 3" TV, but what does it all mean exactly?
Well, it's one of the problems we have when we are looking to buy a new television - the seemingly endless stream of technical jargon that gets sent our way.
We don't understand it, and the person trying to sell you that new TV doesn't seem to understand it either.
The thing is, most of this stuff we don't really need to understand.
Much of it is just fancy terms and numbers to make that expensive new purchase of yours sound more exciting!
However, learning a little about the jargon can improve our understanding of the technology, and can sometimes help us get the best from it.
So what's the aspect ratio of your television all about?
When referring to televisions, the aspect ratio essentially tells us the shape of a TV image - and is also used to refer to the shape of our televisions.
The ratio that it refers to is the width of the image divided by the height.
For those of you old enough to remember (ok, we're not actually going that far back!), the traditional shape of a television screen was almost square.
It was slightly wider than it was high, but not by much.
This TV screen shape was designed to match the shape of the images that were sent to our TVs.
It was known as a "4 by 3" image - also known as 4:3 or 4x3.
This means that the image was 4 units wide and 3 units high.
The physical size of the units doesn't matter - it could be 4 inches by 3 inches, 4 feet by 3 feet or 8 feet by 6 feet. But, the relationship between the width and the height is always 4 across and 3 down.
As the actual size of the image doesn't matter, it is often easier to express this 4:3 relationship as a ratio. This means that if we divide the width by the height, then 4 ÷ 3 = 1.33.
So 1.33 (or 1.33:1) is said to be the aspect ratio of a 4:3 TV image or television.
You will often find the aspect ratio referred to as either of these two numbers, but they both mean the same thing.
When you do see these terms, then it is just telling you the basic shape of an image or screen.
As with all technology, times change and the boffins try and improve on what we already have.
Therefore, it was thought that this traditional 4:3 aspect ratio used in television viewing could be improved.
Although originally 1.33:1, the traditional aspect ratio of movies has long been different to the 'square' images were used to seeing on our televisions.
This meant the image shape was much wider than it was high. You can see this by the wide shape of the screen in a cinema or movie theater.
This wide image shape was thought to more closely reflect the way that our eyes worked - and so was a more natural way for us to see things.
With the introduction of HDTV and digital television, the result has been a slow but steady switch to 'widescreen' televisions.
These days, all new OLED and LED TVs are now widescreen.
The widescreen image we see on our TVs isn't quite the same shape as they use in movies, but it is similar.
The actual shape that has become standard for HDTVs is a "16 by 9" image.
This is the standard HD aspect ratio. As with a 4:3 image, this means that the picture is 16 units wide and 9 units high - therefore much wider in comparison to the height.
You're probably way ahead of me now, but we can also express this widescreen image as a ratio.
Therefore, 16 ÷ 9 = 1.7777.
This number is usually rounded up to 1.78 - so when you see a reference to 1.78 or 1.78:1, then you know that the image or TV screen will be widescreen - or 16:9.
So now we've learned a thing or two about the TV aspect ratio, we can feel more confident about another piece of jargon that we will come across.
Most new televisions and computer screens are now being made in a widescreen aspect ratio, so it is good to know a little background about it.
This understanding of aspect ratios is probably more useful when it comes to talking about the movies that come on Blu-ray players and DVDs.
We can use it to understand how it affects what we see on screen. You can find more about this in my article on the aspect ratio of DVD and Blu-ray.
Paul started the Home Cinema Guide to help less-experienced users get the most out of today's audio-visual technology. He has worked as a sound, lighting and audio-visual engineer for around 20 years. At home, he has spent more time than is probably healthy installing, configuring, testing, de-rigging, fixing, tweaking, re-installing again (and sometimes using) various pieces of hi-fi and home cinema equipment.