Aspect ratio - refers to the horizontal and vertical dimensions of a screen. There are two ratios available for television: 4:3 for the traditional analog TV and 16:9 or widescreen TV commonly used for HDTV. For film, the popular aspect ratio is 2.35:1. It should be worthwhile to note that 16:9 is a compromise between analog TV’s 4:3 and cinema’s 2.35:1. The reason it was selected is so that both analog TV and cinema materials can be viewed in 16:9 displays with minimum wastage of screen real estate. All new HDTV displays are now capable of displaying 16:9 widescreen content. Widescreen can also apply to computer displays, which can also be used to view widescreen movies.
There has been a rapid growth on the sale of 16:9 displays in the past few years because there is a corresponding increase in the availability of HD material from satellite, cable, terrestrial and lately IPTV broadcast systems. HD DVD and Blu-ray disc players also were introduced in the market with the former eventually losing the format battle for HD optical disc media. Other recent sources of 16:9 content are video gaming consoles like PlayStation 3 and Xbox 360, and internet digital set-top boxes like the Apple TV. Even consumer camcorders now available are HD-capable and all these developments are making the widescreen more of a necessity at home.
These times can be said as a transition period from analog TV to digital TV with the introduction of digital TV sources and gradual phase out of analog sources. Some countries have shut down their analog TV transmissions with some scheduled to do it in the very near future. While the transition is going on, we will have both 4:3 and 16:9 sources and displays in our midst. So how do we view a 16:9 material in a 4:3 monitor (or vice versa)? There are screen formatting methods developed to address these issues that will be discussed in the following paragraphs.
Anamorphic - formatting is a video encoding method wherein a 16:9 image is horizontally squeezed to fit inside the available area of a 4:3 display. When viewed without adjustment, the anamorphic image will look compressed, such that the objects in the screen will look stretched vertically. To view properly, the letterbox setting needs to be activated either in the display device or the source, such as a DVD player. Black bars however will appear at the top and bottom of the image to obtain an image without distortion. Most movie titles in DVD include a data marker that indicates whether the content is available in both anamorphic and widescreen versions so it can be viewed properly in both 4:3 and widescreen displays.
Pillarboxing - is the reverse of letterboxing. This is used to properly display a 4:3 content into a 16:9 monitor. Black bars are placed on the sides of the 4:3 image so it can be viewed without distortion in a widescreen display. Some digital TV stations transmitting HDTV content make use of these blank areas when original content is only SD by displaying auxiliary information like weather, stock market figures and breaking news. This same approach is also being used by some analog TV stations who wants to transmit HDTV content that will be displayed in 4:3 TV sets. They utilize the blank areas on top and bottom of the letterboxed 16:9 content to also display auxiliary information.
Windowboxing - is another screen formatting process that occurs when both letterboxing and pillarboxing are utilized. It happens when a 16:9 content is converted to 4:3 letterbox format, but then shown on a 16:9 display device. The result is an image presented in the central portion of the screen with black borders all around the image. Some HDTV displays also have means to crop, zoom, or stretch the a 4:3 content so that it fills the whole screen. Although these methods remove parts or distort the picture, many viewers prefer them than seeing black bars on the edges of the image.
If you are planning to buy a new TV display, we recommend that you go HDTV because all units available now are capable of displaying 16:9 or widescreen images. It is not advisable to invest anymore on 4:3 displays because they will soon be obsolete and because HDTV is the future of television. More and more contents are now becoming available in HD and viewing in them in 4:3 displays with the black bars is such a waste of screen real estate and power consumption. But don’t throw away yet your old 4:3 TV set. You can use it as a back-up for your 16:9 TV set and also for viewing 4:3 content that will still be with us for a number of years more until the transition to digital TV is completed.