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Updated , Mehdi Azzabi

What is the Aspect Ratio?
(4:3, 16:9, 21:9)

The aspect ratio refers to the proportions of the height and width of an image. It defines its overall shape, and it is usually shown as W:H (W is the width and H is the height). The most common aspect ratio today is 16:9, which means that if the width is divided into 16 equal parts, the height of the TV or picture should be 9 parts.

16:9 works great for TVs since that is the format modern TV shows are delivered on, but most movies are made using the cinema standard, which is 21:9. 21:9 is much wider, so parts of the screen need to be filled with black bars above and below the image in order to fit most TVs. These horizontal bars a called "letterboxes". Similar to movies, TV shows used to be made using a 4:3 aspect ratio, which is a lot more square than current TVs (this is why 16:9 is often called a widescreen aspect ratio). To fit modern TVs, vertical black bars or "pillarboxing" is used. We've listed the most common aspect ratios in this table, but every TV sold today uses 16:9.

In theaters, this is why the screen grows wider at the beginning of a movie. Ads shown before the movie follow the TV ratio of 16:9, while the movie itself is 21:9.

Aspect Ratio

Uses TVs
4:3 1.33:1 Standard Channels Old TVs
16:9 1.77:1 HD Channels The majority of HDTVs
21:9 2.35:1 Most movies Most theaters
14:10 1.4:1 IMAX Film Very few theaters
19:10 1.9:1 IMAX Digital Most IMAX theaters
The most common aspect ratios in the video industry.

What do the black bars look like on TVs with different aspect ratios?

Black bars on different aspect ratio

Black bars fill the extra space when the aspect ratio of the screen and content do not match.

Black bars appear when the aspect ratio of the content playing isn't matched with the aspect ratio of the TV.

Depending on the type of mismatch between the picture and the display's ratio, the black bars appear in different places. Content wider than the screen it is played on will have horizontal black bars, while content that is taller will use vertical bars.  The following picture shows the black bars for various televisions and aspect ratios (4:3, 16:9 and 21:9). All televisions have the same diagonal length.

As you can see, when you watch a 21:9 movie on a normal 16:9 widescreen TV, you will have some black bars at the top and bottom. This is represented by the top center TV in the illustration.

Cropping

Original 4:3 picture

 Original picture

Stretched to fit

Cropped to fit

If you do not like having black bars, you have two options available within the settings of your TV: cropping or stretching.

  • Cropping the picture is the equivalent of zooming, but will result in the sides of the picture being removed.
  • Stretching retains all the information but it distorts the image to fit your screen.

Different TVs have different settings for this, so here's a table with the different options found on different brands, as well as their specific name. Some of them have two types of zoom; either two levels of crop or one of them combines both zoom and stretch at the same time.

Brand Stretch Crop Crop #2
Sony Full Zoom Wide Zoom (Zoom+Stretch)
Samsung Fit to screen Zoom/Position N/A
LG 16:9 All Direction Zoom Vertical Zoom (Zoom+Vertical Stretch)
TCL Stretch Zoom Normal (Overscan feature)

IMAX Aspect ratio

IMAX scene in Interstellar

16:9 scene in Interstellar

IMAX movies and theaters are a complete ecosystem that encompasses everything from cameras, speakers, room shapes, screen finishes and even film types. More importantly though, part of IMAX's proprietary system is their own aspect ratio. IMAX has a few different ratios used now to accommodate for different types of rooms, but there are two major ones: 1.9:1 and 1.4:1.

  • 1:9:1 is meant for more standard digital projectors and is used in IMAX Digital theaters. It is a bit taller than the standard Cinema 2.35:1 (21:9) ratio.
  • 1.4:1 is the more iconic ratio. It is the incredibly tall and almost square in shape. This is what IMAX is most known for since the screens are usually much larger than normal cinema theaters and the height makes them a very immersive experience.

Most movies today that use IMAX still are filmed with a mixture of 21:9 ratio and 1.4:1 IMAX. As seen in the picture above, IMAX content fills up the entirety of the 16:9 screen. The image itself goes beyond the height of a 16:9 TV, but it is cropped in Blu-ray films to fit the screen. You don't get the whole experience, but you still get a more complete picture than if it was letterboxed to the standard cinema ratio.

What are 21:9 ratio TVs?

Comparaison between 21:9 CinemaWide and 16:9 television

A 58" 21:9 TV is equivalent to a 61" for 21:9 media, but only 47" for 16:9 media.
Nowadays, the 21:9 ratio is only found on PC monitors. It roughly equates to two 4:3 monitors side by side. Some PC monitors go even wider, causing even 21:9 movies to have vertical black bars. These are good for both productivity and immersive gaming.

21:9 TVs were made a few years ago and were aimed at cinephiles since they match the standard motion pictures aspect ratio and allow you to watch movies from edge to edge of your screen. They aren't available anymore, and they were rare even at the time of their release. Unless you only turn on your TV to watch movies, you're better off with a standard 16:9 TV. Watching normal TV shows on a cinema-wide screen causes it to show black bars on either side, which isn't great. This reduces the viewing area for 16:9 content considerably. A 58" 21:9 television corresponds to the same viewing area as a 47" TV for 16:9 content, as you can see in the illustration.

Conclusion

TV shows are made and distributed using a 16:9 aspect ratio, and every TV sold today uses the same. Movies are usually found with a 21:9 ratio, however, which causes them to have black bars above and below the pictures on standard TVs. Some PC monitors share that ratio, but it isn't very practical on a TV since normal content would have vertical bars.

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Questions & Answers

20 ANSWERED QUESTIONS
90
When I download a 1080p movie, the resolution is not 1920x1080 but 1920x800 and there are black bars on my screen. Why?
This is normal. The official resolution of a 1080p Blu-ray is indeed 1920x1080, which corresponds to an aspect ratio of 16:9. However, most movies are shot in 21:9 instead. To fit this on the Blu-ray format, black pixels are used at the top and bottom of the picture. When encoded for the internet, most people strip those black bars, which results in a 1920x800 resolution.
58
What is widescreen aspect ratio? 21:9?
16:9 is generally considered widescreen.
37
How much area are the letterbox bars supposed to cover on a 16:9 TV?
It depends on the aspect ratio of your media. If it is a 21:9 movie, the bars are a few inches tall, as shown in the illustration above.
26
What is 2K?
2K can mean multiple different things. Some people use it as a synonym for 1080p, while others will assign it to a resolution like 2048x1080, or other resolutions that are between 1080p and 4k UHD.
UPDATE: We've updated this answer to make it a broader definition of 2k.
24
When talking about aspect ratios, can you explain why we have 1.33:1, for example?
1.33:1 is just 4:3, but normalized (4 divided by 3 equals 1.33).
24
Which TVs have aspect ratio auto-switching?
All TVs should be able to do this, but they will handle the process differently from model to model. You might even find the individual ports of some TVs handle aspect ratio auto-switching differently from each other.
23
Will the standard aspect ratio change from 16:9 to 21:9? Just like it did from 4:3 to 16:9?
Not in the foreseeable future for TV shows. Most movies are 21:9, though.
17
I'm really considering the Lenovo B750, which has a wide screen (21:9, to be exact). I would maybe watch some Blu-ray DVDs on it from time to time. I really like the idea of more real estate while surfing the web. Guess I am just nervous since some people like it and others dislike it.
We haven't reviewed that monitor (we currently only review TVs). The additional real estate when surfing the web isn't really useful in 21:9, though, because there are no websites designed for this. Therefore, you will most likely browse the web without full screen, which kind of defeats the purpose of the extra width of the screen.
15
On my 32 inch TV, I notice that a 720p/1080p video plays and looks fine meaning that the people, animals etc look proportionate. However on a 23 inch TV, I have noticed that when playing any 720p/1080p videos, the people, animals etc look stretched vertically when covering the full portion of the screen. My question is are there standard sizes like 32 inch, 40 inch, 60 inch etc on which the proportion of the people, animals will look just fine without having to stretch or crop etc? If yes, what will be the best method to know it?
It doesn't depend on the size of the TV, but of its aspect ratio. Assuming you have a 16:9 23", the problem might just be the crop/stretch/zooming option. Look for a setting named 'Picture Size' or something similar and try different values.
14
I have a 65 inch Samsung 1080p 240 Hertz. I buy a lot of Blu ray movies and i would like to watch them without black bars on the top and bottom. how would I go about doing this please help.
Press 'Tools' on the remote, then 'Picture Size' and select 'Zoom'.
13
Does a 4k TV have a 21:9 ratio?
No. A 4k TV has a ratio of 16:9 (3840x2160).
10
If 16:9 ratio has a resolution of 1920x1080, what resolution does a 21:9 ratio have? When I use a monitor with a ratio of 21:9 and a resolution of 2560x1080 (LG 34UM65-P), is the picture ok? With which resolution will the monitor display the movie? 1920x1080 or 2560x1080?
1080p 21:9 movies have a resolution of 1920x800. Your monitor has more pixels than a movie. When you use it to view a movie in full screen, the video is upscaled 1.35 times (both directions), so it will fill all 2560x1080 pixels. This is not an issue, even if there is no 1:1 pixel mapping.
10
The answer is not entirely wrong, but incomplete: 2k is a bit of a broad term. 2k can also stand for 2048x1080, and a few other resolutions with anything between 1920 and 2048 as the horizontal pixel value. Vertical pixel values can also vary. They are not restrained to just 1080! Example: 2048x858 for CinemaScope-cropped DCI 2K.
The definition being so broad means that watching a 2k movie in a common projection resolution on a "2k" monitor can lead to resizing and letterboxing.
Good point. We'll update the answer to make it clear that there are multiple meanings. Thanks! UPDATE: Corrected one of the incorrect resolution suggestions.
9
I have 65 inch tv in 16:9 full pixel mode the letter box bars are about 4 inches each when playing 21:9 movies, which comes out be approximately 25 % of the screen. In comparison with my old 60 inch it appears the bars are covering a lot more area, is this possible or I am just analyzing too much?
In full pixel mode, this sounds about right. You can always choose a zooming/cropping option if you don't want to bars to show, but you will lose part of the picture.
7
Hello. Do 4K TVs eliminate the problem with aspect ratios? Will any movie I watch be displayed in an aspect ratio of 21:9?
No. Aspect ratio is a description of the screen's proportions, and is independent of the screen's resolution. A 4k TV with an aspect ratio of 16:9 can still only display a 21:9 signal with black bars on the top and bottom of the screen.
7
Is there any way to change the aspect ratio of a Sharp XR-llXC projector from 4:3 to 16:9?
Your projector native aspect ratio is 4:3 and that can't be changed. By default, it will display 16:9 content with black bars on top and bottom of the screen. The 'image shift' function of your projector can remove one of the black bar but not both. You could also see if there is special anamorphic lenses available for your projector. Those lenses, with the help of a software, could convert 4:3 to 16:9 but with some degradation in the picture quality.
7
Why don't TV manufacturers make their televisions 21:9 capable instead of 16:9? Is it a cost/money thing?
TVs are still geared more toward watching TV shows and playing video games (16:9) than they are to watching movies (21:9), so it's less about cost and more about the manufacturers tailoring to what most people want.
7
4K is not a 16:9 ratio. 4K is not 3840x2160. 4K is 4096x2160. 4K is 17:9. 3840x2160 is UHD (UltraHD) 16:9.
You are technically correct. But now, '4k' is a broad term which refers to a resolution of about 4000 horizontal pixels. When talking about TVs, this is a resolution of 3840x2160 and you will see it in all the brands advertising (Samsung, LG, Sony) where they include one or both terms (4k and UltraHD). The standard for films is different.
5
This question is for games. Will a monitor that is 21:9, 3440x1440, actually show more on the sides than a 4k 16:9 monitor?
As long as your source device can output that resolution and the game also supports that resolution then yes, it would.
5
The screen I show my Windows Live Movie Maker on is 22" wide and 14" high. Should I use 16:9 or 4:3 aspect ratio?
4:3 will fill up a little bit more of the screen, so use that.
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