Aspect Ratio is defined as the relative relationship between the width and height of some object. It applies to images, videos, menus and shows within ProShow and can have a significant impact on video output.
Aspect ratios are typically displayed as two numbers separated by a colon (:) or x and they describe the length of an object relative to its height. A modern widescreen HDTV for instance typically has an aspect ratio of 16:9. This tells you that if the width of that TV were broken up into 16 equal units of length the height would necessarily be equal to 9 of those units. Another common way of expressing these ratios is by breaking them down to their single unit equivalency; 16:9 is roughly equal to 1.7778:1. An older SD (standard definition) TV can be expected to have an aspect ratio of 4:3, roughly 1.3333:1.
Although this concept applies to many things in ProShow, the places it has the most effect are in show layout and video output. Getting all your aspect ratios to match is the best way to avoid problems.
What is the right aspect ratio for my show?
The best aspect ratio to use for any show depends on where, and how, that show will be played. The Blu-ray format for instance uses 16:9 videos and can be expected to be played on a widescreen TV. Shows intended for that format should be created at 16:9. A DVD supports 4:3 and 16:9 ratios interchangeably, but if you know the disc will be played on an older SDTV then it’s best to work with a 4:3 show. The idea is to match the aspect ratio of a show to the aspect ratio of the intended playback device and to use an output format that supports that ratio.
While video output will always have a set aspect ratio, specified at the time of creation, non-video formats (Executable, Web Show, ProShow Sharing, etc.) effectively use the show aspect ratio as the output aspect ratio. There is no need to do anything special during output to ensure a match.
How do I set the aspect ratio for a show?
The aspect ratio of a show can be set when the show is created by using the Aspect Ratio option under the Blank Show area of the new show creation dialog. It can also be set under the Show Settings area of Show Options. The aspect ratio of a show can be changed at any time during the design process. Once the show is output, however, that ratio is set for that individual output file. The show can always be updated later and re-output, but for any given output attempt a show can be at only one aspect ratio.
It is also important to keep in mind that changing the aspect ratio of a show changes its layout. If a show switches from 16:9 to 4:3, for instance, then there will be less horizontal area and a layer / caption that was previously displayed properly may now be cut off. Anytime the aspect ratio of a show is changed it’s important to give the show at least a cursory watch to be sure there are no unintended problems.
What happens when aspect ratios don’t match?
Aspect ratios can be mismatched in a few different ways, some worse than others.
The most common aspect ratio mismatch occurs when a video output file has a different aspect ratio than the playback device on which it is displayed. Most people have seen this type of mismatch at some point while watching a Hollywood movie on a TV. The padding typically appears as blank (black) space on opposing sides of the video. When the padding is at the top / bottom it’s called letterboxing and when it’s at the left / right it’s called pillarboxing. This type of padding is added during playback so it can differ between playback devices or displays. There is no way to fully prevent this type of padding unless you know where a show will be played before it is output to video.
Another fairly common aspect ratio mismatch occurs when a show has a different aspect ratio than the video file into which it is being encoded. In this case padding (letterboxing / pillarboxing) is encoded into the video stream itself and is seen on all playback devices. Keeping the aspect ratio option in the video file output process matched to that of your show will ensure against this type of padding. Shows can experience both types of padding, which leads to some odd-looking playback, so you want to prevent show / video aspect ratio mismatches whenever possible.
The worst type of aspect ratio mismatch can occur when a video output file uses a resolution that differs from its own aspect ratio. This creates distortion in the video stream that can effectively ruin a show. When creating video through the Video File output option you’ll want to keep the resolution in step with the aspect ratio. Remember that aspect ratio is simply a relationship between two values. You can always use division to break down a larger resolution value to see if it matches the a given aspect ratio. Just divide the first resolution value by the second (1920 divided by 1080) and do the same with the aspect ratio (16 divided by 9). If the results match then the resolution and aspect ratio match. There are some exceptions, like DVD-formatted MPEG2 files, but generally speaking this is a good rule of thumb.
How are menus affected by aspect ratios?
Menus can have the same type of padding seen in show playback. The effect is generally considered less severe, but for proper playback it is best to match the aspect ratio of your menus to that of the shows they’ll be controlling. This creates a nice seamless transition from show navigation to show playback. The menu’s aspect ratio setting can be found in the Menu tab of the appropriate output dialog (DVD, Blu-ray, etc.) and is usually set to match your show’s aspect ratio automatically.
Do I need to worry about layer aspect ratios?
Generally speaking, no. The aspect ratio of a layer defaults to Auto and that works in almost every instance. Some rare videos might import at the wrong aspect ratio and in those cases adjusting the Aspect option under the Layer Settings tab of Slide Options can have a beneficial impact. Most people never have reason to adjust this option.Note that layer scaling and layer aspect ratio are different. Scaling controls how a layer is sized within the show area. Aspect controls the dimensions of a layer independent of its size.