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So you went out and bought yourself a new HDTV. Many of you bought a sound system to go with it. Now you are inundated with all kinds of terms and acronyms. In this series we will go through the jargon associated with your new system. While these articles are aimed at newbies, some experienced readers out there may learn a thing or two as well. Today we start with a topic that comes up on our podcast ( HDTV and Home Theater Podcast) quite frequently.


Aspect Ratio

The second topic for discussion is Aspect Ratio. We'll go through the some of the basics for newbies and maybe even throw in something for our more experienced readers.

Aspect Ratio defined - The ratio of width to height of a screen. Analog TV in the US and most of the world is 4:3. That means for every four units wide a TV is, it is 3 units high. For HDTV, the aspect ratio is 16:9 which means for every 16 units wide the TV is, it is 9 units high.

So why was HDTV chosen to be 16:9 and how come I still have black bars on my DVDs?

Cinematic movies are not shot in 16:9 (or 1.78:1) so why did the HDTV specification chose this aspect ratio? Note - when talking about TV the aspect ratio is given in either 4:3 or 16:9, when talking about cinematic films the aspect ratio is obtained by dividing the width by the height. So when you read a DVDs information and see that its aspect ratio is 1.78:1 you know it will fill your entire screen. If you see 1.33:1 then you know its a 4:3 or Full Screen movie.

The reason 16:9 was chosen was that when you take all the cinematic aspect ratios and lay them on top of each other 16:9 turned out to be the best compromise. It minimized the amount of unused screen when all aspect ratios were considered. As a result your new wide screen TV could end up with black bars at the top and bottom. But these black bars are much less than what you would see on your old 4:3 TV.

But some movies are not shot in 1.78:1 and yet they fill up the entire screen on my new Plasma TV. This happens when some studios master the DVD for wide screen TVs. They will actually crop the film to fit perfectly on your screen. This bothers many film aficionados who prefer watching movies in their Original Aspect Ratio (OAR). Some DVDs will have this acronym contained in the movie details to help consumers quickly identify that the movie is not cropped. Some pay movie channels will also crop the movie and this has drawn the ire of many. Yet others say, I paid for all that screen real estate so I want the pixels doing something.

Common Aspect ratios and their uses

CinemaScope - 2.35:1 or (~14:6) - Developed by 20th Century Fox, which is the only studio still using it. The original Star Wars Movies were filmed in CinemaScope

Panavision - 2.40:1 or (12:5) - Developed by Panavision and became very popular in the 1970s. Today they make lenses for movies with a 1.85 or (18.5:10) aspect ratio.

Academy - 1.33:1 or (4:3) All movies were actually 4:3. When TVs came on the scene they were designed to this specification. Movies then moved to wide screen to differentiate themselves from television. The Robe was the first movie to be filmed in wide screen.

Other film formats include Todd-AO, 2.2:1 (Oklahoma in 1955), Metroscope, 2:1 (Dirty Dozen), Cinerama, 2.8:1, (How the West was Won 1962), and there are others that that you can find out about by following this link (http://en.wikipedia.org/wiki/Aspect_ratio_(image) ).

Posted by The HT Guys, January 29, 2008 10:39 AM

About The HT Guys

The HT Guys, Ara Derderian and Braden Russell, are Engineers who formerly worked for the Advanced Digital Systems Group (ADSG) of Sony Pictures Entertainment. ADSG was the R&D unit of the sound department producing products for movie theaters and movie studios.

Two of the products they worked on include the DCP-1000 and DADR-5000. The DCP is a digital cinema processor used in movie theaters around the world. The DADR-5000 is a disk-based audio dubber used on Hollywood sound stages.

ADSG was awarded a Technical Academy Award by the Academy of Motion Picture Arts and Sciences in 2000 for the development of the DADR-5000. Ara holds three patents for his development work in Digital Cinema and Digital Audio Recording.

Every week they put together a podcast about High Definition TV and Home Theater. Each episode brings news from the A/V world, helpful product reviews and insights and help in demystifying and simplifying HDTV and home theater.