In our last program, you’ll recall, we introduced the concept of aspect ratio and we looked at the origins of the 4:3 aspect ratio in particular.  In this program we’re going to talk about the other, and I would say more important aspect ratio in digital video, 16:9.  Now, why 16:9, why this particular shape and why did it go wider?  Well let’s trace this one back as well.  We’ll go back to the history of film, but this time we’ll jump ahead a bit to the 1950s, and look at the influence of television on this industry.

Now television had been around for awhile, but it really wasn’t until the post-war prosperity boom and the newly suburbanized middle class, that there was a large enough audiences who were staying at home and who started to buy televisions in decent numbers. This of course took a serious bite out of the movie-going audience, and that made the film industry very nervous.

So what followed then was a flurry of invention on the film industry's part to get that audience back, and what better way than to take advantage of these big dark rooms and make the movie picture bigger, and better and wider?

Now just as a point of reference, you'll remember in the silent movie era the aspect ratio for film was 4:3 or 1.33.  With the advent of sound being added to film in the 1920s, the imaging area was reduced to accommodate for the addition of the sound track on the film plane, and this changed the aspect ratio slightly, from 1.33 to 1.37 - not a big difference, but it did establish a new standard for film, called the Academy Standard.

So just so you know and to avoid confusion; when one talks about aspect ratios for video, the convention is use to the ratio of two whole numbers, like 4:3 and 16:9.  But in talking about the ratios for film, the convention is to use a decimal ratio like 1.33, 1.85, 2.35, etc.

So, back to the 1950s,  the motion picture industry began to come up with all kinds of new and competing wide film formats with compelling space-age names like Vista Vision, Cinerama and Technirama.  There are whole books written on this phenomenon, but we'll just cut to the chase and say that after the 1950s were over, some of these widescreen ratios took hold as standards, thus giving us a wide range of aspect ratios in use in the film industry: 1.37, 1.67, 1.85, 2.20 and 2.35.

Now, you can see that the relatively vertical 4:3 aspect ratio of television means that there were some serious compromises that need to be made in order to view wide-format film on those screens.  So when the standards for high-definition television were being hashed out in the early 1980s, it was agreed that a corresponding widescreen format for video should be established as well. 

Enter Dr. Kerns Powers, of the David Sanroff Research Center in Princeton, NJ, a leading research lab on the advancement of television.  Dr. Powers took a look at all of the major aspect ratios in popular use and mapped them together as we did here.  He then discovered something interesting.  If he took a rectangle of a certain proportion and scaled it two different ways, he could encompass both the width and the height of all the other aspect ratios.  That magic rectangle had the proportions of 16 units wide by 9 units high, or 16:9.  This discovery was adopted and 16:9 was set as the new aspect ratio standard for High Definition Television.

Now unless you've been living in a cave, you know this shape as well, because 99.9% of all new high-definition, flat-screen, televisions have a 16:9 display.  In program 4 we'll talk more about widescreen and the technical issues we all have to face when we deal with various and sundry aspect ratios.

notes:

Another great on-line resource for this subject is the cheeky American WideScreen Museum.

HUGE thanks to the family of Dr. Powers, who kindly answered my letter and provided the photo and the permission to use it.

Thanks also to the IEEE, who forwarded my inquiries to the Powers family.

Josh B., thanks for spotting the post on the DV Info Net which subsequently gave me the lead to the 16:9 question. I know I’ll be leaning on Chris Hurd and the guys at the DVi Network a lot in the future. It’s an excellent group of people.