Blu-ray and DVD aspect ratio formats can be tricky to figure out.
4 by 3, widescreen HDTV aspect ratio, letterboxing - there are many issues to understand.
So why should we care?
Well, they can help to explain a common issue for many people - those annoying black bars that sometimes appear on the TV screen when we watch a movie.
There is a reason why we sometimes see these black bars.
The main thing to understand is that there is a fixed aspect ratio for your TV and an aspect ratio that the film was recorded in.
These might be different.
We have already looked at the basics of aspect ratios in the article understanding the TV aspect ratio.
To summarise, that guide took us through what an aspect ratio is, and showed us the two most common aspect ratios for our television screens, 4:3 and 16:9.
This is a fixed ratio that is set by the physical structure of the TV screen you have purchased. The most common aspect ratio today is 16:9 - or 16 units across the top and 9 units down the side.
If you divide 16 by 9, you get 1.7777. This number is rounded up to
1.78, and is often used to express the widescreen aspect ratio - 1.78:1.
No matter how big your screen is, this ratio between the width and the height will be the same.
Go and take a look at that article first if you don't understand this point.
So once we know that there are two main TV aspect ratios, it brings us to another interesting issue - how do the aspect ratios of the Blu-rays and DVDs that we buy affect what we see on our screens?
Also, if you like to read the manual of your equipment (unlikely) - or just like to flick through the setup menus changing every setting as you go (more likely) - then you will know that DVD/Blu-ray players and HDTVs often have the ability to alter the aspect ratio that you see on the screen.
So we will also mention some changes you can make to get a better (or worse!) picture.
If you look at the back of the box of your Blu-ray or DVD disc, it will tell you the aspect ratio of the movie or show that is on the disc.
When a movie or television program is recorded, a choice is made as to the aspect ratio that it will be recorded in. Although there are many different aspect ratios that have been used over the years, there are four main formats that you will come across regularly.
Also known as 4:3 (pronounced 'four by three'), this is the traditional aspect ratio of standard-definition TVs and images.
This is becoming less common as modern TV screens switch to widescreen formats. However, many older TV programmes will only be available in this aspect ratio.
Therefore, we can play this 4:3 TV show on our 4:3 television and it will fit perfectly.
However, if we play the 4:3 TV show on our 16:9 television, then will see the black bars as shown below.
On the 4:3 TV, the image is a perfect match and fills the screen completely.
But, on the 16:9 HDTV, there are bars on either side to make up for the missing width of the image:
This is called pillar boxing or vertical letterboxing.
Most HDTVs will have a 'justify' (or similar) option where it will stretch the image to the edges, but this can make the image appear strange.
Another alternative is to zoom in and remove the bars, but this will mean losing some of the action at the top and bottom.
The picture may also lack sharpness when you zoom or justify the image.
Also known as 16:9 (pronounced 'sixteen by nine'). Also commonly just called widescreen - even though there are other common aspect ratios which are also 'widescreen'.
This can be thought of as the HDTV aspect ratio, as this is the standard format for high-definition television - and you will find TV companies recording new HD programmes with this ratio.
The widescreen image will have bars at the top and bottom on a 4:3 TV - and the image will appear to be much smaller as it is made to fit the smaller width.
This is called letterboxing. We can zoom in on the TV to get rid of the bars, but this will mean losing some of the action at the edges - and make the picture lose sharpness.
But, as you can see below, the 1.78:1 image on the 16:9 TV (below) is a perfect fit. Doesn't that look great!
Notice that with a widescreen image, you get to see more detail on the left and right edges of the picture compared to the 4:3 version shown in the previous section.
A common widescreen aspect ratio for many movies is 1.85:1. It is a common standard in the US for widescreen movies. This is slightly wider than the standard 16:9 widescreen image.
However, a movie with this aspect ratio will fit quite well on a standard 16:9 high-definition TV screen as it is almost the same shape.
A 1.85:1 movie on a 16:9 screen does actually have some letterboxing, but as this shape is a pretty good fit the bars at the top and bottom will be quite small.
In fact, with overscan on, you won't actually see them at all. If you turn overscan off, you will get small bars at the top and bottom - but you also get a bit more of the image left and right.
Below, on the 4:3 television the result is very similar to the one with the 1.78:1 aspect ratio.
However, the black bars at the top and bottom will be slightly bigger - and therefore the actual image will be smaller. We can zoom in to remove the bars - and some of the action too!
Also known as Panavision or CinemaScope. A popular aspect ratio for major movie releases.
Historically, this aspect ratio was actually 2.35:1, but it switched to 2.39:1 in the 1970's. It is also commonly rounded up to 2.40:1.
Therefore you may see any of these three versions recorded on the DVD box - although they are essentially the same thing.
Notice that we can see even more detail on the left and right of the image compared to the widescreen version.
The 4:3 television will have huge black bars at the top and bottom. The movie will be that small colorful bit somewhere in the middle!
Again, as with the previous aspect ratios, zooming in can reduce the bars but it will also make the image less-defined and cause a loss of the picture at either side.
On the 16:9 TV, below, this is probably the one that annoys people most.
We spend all this money on a huge 60-inch widescreen technological phenomenon, and then when we play a DVD or Blu-ray part of the screen is covered with black bars at the top and bottom!
I guess we should have tried to find a 1.85:1 version of the movie!
If we want to keep the aspect ratio in the way the director intended, then we have little choice but to watch it with the letterboxing.
Alternatively, we can zoom in the image to remove the bars, but we will then lose some of the action from left and right - and after all, having this extra width is the whole point of shooting the movie in 2.39:1.
Another option is to get a screen that is the same 2.39:1 aspect ratio.
Unfortunately, although there have been a few released in the past, I'm not aware of any current ultrawide flat screen TVs.
There are a few smaller ultrawide 21:9 monitors which you could use - which is almost the same aspect ratio.
If you really want to go down this road for home theater, the best option is probably to buy a projector and a screen that supports this wider aspect ratio.
Some popular options are the STR-235125 Silver Ticket 2.35:1 Projector Screen or the Elite Screens Aeon Series 125-inch 2.35:1 Borderless Projector Screen.
It can be quite confusing when we start thinking about the Blu-ray or DVD aspect ratio.
As there are a few different variations, it can be difficult to understand why the picture sometimes looks different on our television screens.
However, when you understand what is happening with your TV screen, and why, then it isn't so difficult to see what is going on.
The main benefit of understanding this issue is that you can look out for the aspect ratio of a Blu-ray or DVD disc before you buy it, and you may make a better choice for your TV equipment.
You always have a choice of cropping out the black bars when you watch it on your TV. However, the image will always be less sharp, and you may well lose some of the important action.
Personally, I always watch something at the original aspect ratio. I hate it when an image is stretched or cropped on the screen. However, maybe that's just me!
If you are looking to buy a new Blu-ray player, don't forget to take a look at my guide to the top 10 Blu-ray players in 2019.
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.