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Table of Contents >> Aspect Ratio
The aspect ratio of an image is its displayed width divided by its height (usually expressed as "x:y"). For instance, the aspect ratio of a traditional television screen is 4:3, or 1.33:1. High definition television uses an aspect of 16:9, or about 1.78:1. Aspect ratios of 2.39:1 or 1.85:1 are frequently used in cinematography, while the aspect ratio of a sync-sound 35 mm film frame is around 1.37:1 (also known as "Academy" ratio). Silent films which used the full frame were shot in 1.33:1.
The evolution of film and TV aspect ratios
The 4:3 ratio for standard television has been in use since television's origins and many computer monitors use the same aspect ratio. Since 4:3 is the aspect ratio of the usable frame within the Academy format once the soundtrack had been taken into account, films could be satisfactorily viewed on TV in the early days of the medium. When cinema attendance dropped, Hollywood created widescreen aspect ratios to immerse the viewer in a more realistic experience and, possibly, to make broadcast films less enjoyable if watched on a regular TV set.
16:9 is the format of Japanese and American HDTV as well as European non-HD widescreen television (EDTV). Many digital video cameras have the capability to record in 16:9. Anamorphic DVD transfers store the information in 16:9 vertically stretched to 4:3; if the TV can handle an anamorphic image the signal will be de-anamorphosed by the TV to 16:9. If not, the DVD player will unstretch the image and add letterboxing before sending the image to the TV. Wider ratios such as 1.85:1 and 2.39:1 are accommodated within the 16:9 DVD frame by adding some additional masking within the image itself.
Within the motion picture industry, the convention is to assign a value of 1 to the image height, so that, for example, an anamorphic frame is described as 2.39:1 or just "2.39". This way of speaking comes about because the width of a film image is restricted by the presence of sprocket holes and a standard intermittent movement interval of 4 perforations, as well as an optical soundtrack running down the projection print between the image and the perforations on one side. The most common projection ratios in American theaters are 1.85 and 2.39.
The 16:9 format adopted for HDTV is actually narrower than commonly-used cinematic widescreen formats. Anamorphic widescreen (2.39:1) and American theatrical standard (1.85:1) have wider aspect ratios, while the European theatrical standard (1.66:1) is just slightly less. (IMAX, contrary to some popular perception, is 1.33:1, the traditional television aspect ratio.)
Super 16mm film is frequently used for television production due to its lower cost, lack of need for soundtrack space on the film itself, and aspect ratio similar to 16:9 (Super 16mm is natively 1.66 whilst 16:9 is 1.78).
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Original aspect ratio
Original Aspect Ratio is a home cinema term for the aspect ratio or dimensions in which a film or visual production was produced — as envisioned by the people involved in the creation of the work. As an example, the film Gladiator was released to theaters in the 2.39:1 aspect ratio. It was filmed in Super 35 and, in addition to being presented in cinemas and television in the original aspect ratio of 2.39:1, it was also broadcast without the mattes its original aspect ratio release had.
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Letterboxing and pillar boxing
Letterboxing is the practice of transferring widescreen films to video formats while preserving the original aspect ratio. Since the video display is most often a more square aspect ratio than the original film, the resulting video must include masked-off areas above and below the picture area (often referred to as "black bars," or, more accurately, as mattes). Letterboxing takes its name from the similarity of the resulting image to a horizontal opening in a postal letter box.
Letterboxing offers an alternative to the pan and scan or full screen method of transferring a widescreen film to video. In pan and scan, the original image is cropped to to suit the 1.33:1 (or 4:3) ratio of the television screen. In contrast, letterboxing preserves most of the original composition of the film as seen in the theater.
Pillar boxing refers to what happens when a 1.33:1 image is displayed on a wider screen, adding bars on the side. The pillar box effect occurs in widescreen video displays when black bars (mattes or masking) are placed on the sides of the image. It becomes necessary when video that was not originally designed for widescreen is shown on a widescreen display. The original material is shrunk and placed in the middle of the widescreen frame. "Pillar box", sometimes called windowboxing, comes from the similarity of this display to free-standing mailboxes in the UK and the British Commonwealth.
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Working with aspect ratio in AVS Video Editor
When you work with video files in AVS Video Editor, it is sometimes necessary to set their aspect ratio parameters. You will need to select the initial aspect parameters when you start creating a new project, you can change the video file aspect ratio settings in the properties window and finally, you can use the aspect correction option when you save your video file into the available video formats. See the sections below to get more information on this topics.
Selecting aspect ratio when you create a new project
When you create a new project it is necessary to select the future video image aspect ratio. The fact is, hardware and software DVD players can playback your created DVDs in accordance with their aspect ratio that will not always coincide with the image physical width to height ratio. That is why you should bear this in mind when you create a new project and save your movie later in DVD or MPEG format. You should decide from the very beginning what aspect ratio your movie will have.
When you save your movie in DVD or MPEG format, you can choose 4:3 aspect ratio if you plan to watch your movie using a common television set, or 16:9 aspect ratio to watch your video on a widescreen TV.
When you save your movie in all other supported formats (AVI, RM, and others), it is strongly recommended that you leave Original Aspect setting.
If you have already created a project with the settings like in this one but with other video material and used the Crop function in the video properties, you can set here the crop percentage that will be used by default in your current project. If you need to change it, you can do that later, using the video file properties.
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Changing aspect ratio in video file properties
When you add a video clip to the Storyboard you can view its properties and change some of them if necessary.
In the Aspect tab you can modify the aspect ratio of your video clip. It might be useful if the video was prerecorded with distortions - elongated in horizontal or vertical dimension. You can correct that changing current aspect width and current aspect height, selecting Custom aspect ratio in the
upper drop-down list, leave the Original aspect, or change it to the 4 to 3 or 16 to 9 ratio.
You can also use the Video Crop Scale option to cut out the editor created mattes (black areas), but please note, that a part of image will also be lost. You cannot cut out the mattes initially present in the video material using this function. This function is similar to pan and scan option in DVD players.
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Saving movies using aspect correction
Sometimes your video file aspect ratio does not coincide with the physical resolution width to height ratio. If you leave the parameters this way there can be image distortions during playback. To correct this situation the aspect correction function was introduced into AVS Video Editor. You can use this function when you save your video into all the main formats, except DVD and MPEG. These two formats use the aspect ratio in-built identification and you can set their aspect ratio when you create a new project. For all the other formats three options are available:
Use aspect correction - the Video Editor will correct the initial project frame size to optimally fit the set aspect ratio. For instance, the editor can increase or decrease the video frame height so that the physical width to height ratio coincided with the aspect ratio.
Note: when you convert and save your video file into
3GP format and into
MP4 format for mobile phones, this option is disabled. This is done due to the fact that mobile phones support only videos with fixed frame sizes that cannot be altered in accordance with aspect ratio.
No aspect correction - the Video Editor will correct the initial aspect ratio according to the video file physical frame size ratio. If the aspect ratio is wider than that of the physical dimensions', the editor can add mattes above or below the image (letterboxing). In case the aspect ratio is narrower than the physical dimensions ratio, the editor can add mattes on the sides of the image (pillow boxing).
Resize - free resize with no aspect correspondence. All the aspect related changes will be neglected and discarded. The image will be resized according to the width and height specified.
Appendix
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