Produced by:
| Follow Us  
How and Wide
September 4th, 2003 Posted in Schubin's Greatest Hits by sfelix | Print This Post Print This Post
Originally published in Videography September 2003

Widescreen is the future of videography. So why is this blurb oriented vertically on this page?

The first thing to remember is that shape is not the same as size. The second is that only images have aspect ratios. The third is that what you see is not necessarily what they get.

Those three things to remember are in the realm of widescreen video. It’s a subject so simple that it sometimes becomes unnecessarily complex, as last month’s letters page suggests. And it’s based largely on an error (see “Wide Err,” page TK).

All images have shapes. Leonardo’s Mona Lisa is oriented vertically; his Last Supper is oriented horizontally. Both are masterpieces. Neither shape is better than the other, but one may be more appropriate for a banquet table and the other for a human figure.

Edison’s kinetoscope introduced a shape for moving imagery in the 19th century. It had an aspect ratio (ratio of width to height) of 4:3 or roughly 1.33:1. The Lumiere brothers in France initially used a different shape but changed to Edison’s, and the 4:3 standard was born.

Not all movies were 4:3. There were both wider and narrower formats from the beginning, and even 4:3 movies were sometimes changed in exhibition. The Kinematograph and Lantern Weekly, a publication for movie exhibitors, suggested in 1913 that exhibitors simply crop the tops and bottoms off of already-shot images. “The result is a better shaped picture — more artistic. The portion masked off will never be missed.”

It was sound, however, that first officially changed the aspect ratio of movies. The sound track ate into the side of film imagery, making it less wide. The movie industry recognized a need for a new standard frame. Proposals were introduced for both wider and narrower shapes.

Director Sergei Eisenstein argued for a “dynamic square” that would accommodate both vertically and horizontally oriented shapes as desired. The Society of Motion Picture Engineers tested proposals on a screen 41 feet wide and 23 feet high, an aspect ratio of 1.78:1 (16:9). But the Academy aperture, standardized in 1932, was 11:8 (1.375:1).

That was for movies. Television picture tubes, initially, were round. The largest rectangle that can be placed within any circle is a square, an aspect ratio of 1:1.

When the British established the world’s first video standard in 1937, the aspect ratio was 5:4 (1.2:1). When the U.S. followed in 1941, the National Television System Committee (NTSC) said it was adopting the motion picture standard but chose 4:3 instead of 11:8 (the NTSC did take note of 11:8 Russian standards of the time).

Television hurt cinema. At the beginning of 1948, when there were just 16 TV stations on the air in the U.S., average weekly movie attendance was 90 million. By the end of 1953, when there were 356 stations, movie attendance had dropped to 46 million.

To compete, the movie industry had to offer what television could not: free dishes, color, 3-D, wafted smells, “Tingler” seats — and giant screens. Alas, there was a problem with the last.

Movie theaters had balconies. Those seated under the overhangs couldn’t see the tops of giant screens, and projectors located in booths between balconies couldn’t fill tall screens. So the expansion was largely in the horizontal direction.

Some of the new widescreen-movie systems, such as Cinerama, required new projection equipment and screens. Others could be adapted to existing theaters by using masks in projectors.

Sometimes directors were instructed to fill the wide screen, as in the 1953 CinemaScope feature How to Marry a Millionaire. Other times, there was little concern about the precision of the framing. The exhibitors’ sheet for the 1959 movie Imitation of Life noted that the movie could be shown in any aspect ratio up to 2:1.

For years, there were widescreen movies, and there was television. Then, in 1961, NBC broadcast How to Marry a Millionaire.

Widescreen is fine. Normal is fine. Widescreen on normal (or vice versa) is a problem.

The image may be squeezed so everyone looks tall and thin, a characteristic called anamorphic (literally “up-shaped”). It may also be shrunk, leaving black bands above and below, a characteristic called letterbox (because the image looks like a mail slot in the screen). NBC chose the third basic technique, truncation, chopping off most of the width of the original widescreen image.

Purists say letterbox is the best option because it preserves the original framing. On the other hand, it loses detail and threatens burned-in discoloration (over a long period) where the stripes appear.

It’s also possible to combine techniques. The British Broadcasting Corporation (BBC) combines shrinking with truncation so less detail and less of the sides are lost. The global widescreen-video standard aspect ratio is 16:9 (1.78:1); the BBC uses 14:9 (1.56:1) for its analog broadcast transmissions.

That’s part of why “What you see is not necessarily what they get.” Your widescreen video might be seen squeezed, shrunken, and/or truncated on a non-widescreen display. On a widescreen display, it could be even worse!

Videographers shooting 16:9 sometimes use monitors with widescreen settings, compressing the scanning lines so everything is the right shape. The finer raster can look HDTV-like. But that’s not what home viewers will likely see (at least not for the immediate future).

Letterbox on a normal, non-widescreen display looks small. On a properly adjusted widescreen display, it fills the screen but with only 75% of the vertical detail. On an improperly adjusted widescreen display, the letterbox could become a black picture frame.

Consider a broadcaster truncating the widescreen video to fit non-widescreen TVs. On a widescreen TV, the truncated video needs to be stretched to fill the screen.

Then there’s overscan. Like other TVs, widescreen displays don’t show 100% of the picture that was shot. Videographers are accustomed to framing accordingly. But the top and bottom of a letterboxed image are the edges of what was shot. If a program may be seen on both shapes of displays, it’s necessary to consider both overscan and frame edges. Again, “What you see is not necessarily what they get.”

How about “Only images have aspect ratios”? The corollary is that signals don’t have aspect ratios.
Any video recorder, from VHS on up, can record true widescreen video. If what comes out of the camera is widescreen, then, unless the signal is intentionally changed, so is the recording. Similarly, there is no such thing as widescreen cable, widescreen distribution amplifiers, widescreen routers, etc.

The only difference between a widescreen-capable production switcher and any other is the ability to make a circle wipe look like a circle in either format. Similarly, any character generator can work with either widescreen or non-widescreen images; the only difference is how condensed the font looks.
There’s no such thing as a widescreen lens, either. The <H>16:9/4:3 settings on some lenses simply adjust the magnification to compensate for the smaller chip area used when some switchable cameras are used in 4:3 mode. When a non-switchable 4:3 camera is used with such a lens, the lens actually needs to be set to <H>16:9.

Confused? Consider the common 2/3-inch camera format. Its imagers have an 11-mm diagonal. Lenses for it, therefore, are designed to produce a round image with an 11-mm diameter.

A 4:3 2/3-inch imager is 8.8×6.6 mm. A 16:9 2/3-inch imager is 9.6×5.4 mm. Both have an 11-mm diagonal. Both will work perfectly with 2/3-inch lenses.

Switchable cameras (except for those from BTS/Grass Valley/Philips/Thomson) are 9.6×5.4 mm in 16:9 mode but only 7.2×5.4 mm (with 25% fewer picture elements) in 4:3 mode. The latter does not have an 11-mm diagonal; it has only a 9-mm diagonal, roughly 20% less. A lens focal length of 9 mm, therefore, will behave more like a lens focal length of 11 mm.

The “aspect-ratio converters” on those switchable lenses make the 9-mm focal length on a switchable camera in 4:3 mode look like a 9-mm focal length on a non-switchable 4:3 camera. They don’t make it look like a 9-mm focal length in a camera’s 16:9 mode. They can’t. The shape is wrong. If they matched the width, the height would be wrong, and vice versa.

A 9-mm focal length is both wider and higher than an 11-mm focal length, on any camera, in any aspect ratio. That’s size. But “Shape is not the same as size.” Widescreen is not bigger than normal, as letterbox proves. The Last Supper can be shot with either a widescreen camera or a normal one; so can the Mona Lisa.

So, why shoot widescreen? There is a trend towards widescreen video displays. The transition is moving even faster outside the United States. In Britain, non-widescreen commercials have been illegal for some time.

Unfortunately, not all TV displays are widescreen yet, so widescreen footage may need to be converted. To convert widescreen to a letterbox format, shrink the vertical size to 75% of normal. To convert widescreen to a truncated format, expand the horizontal size to 133% of normal and pan to the desired framing. To convert widescreen to a squeezed format, don’t do a thing.

If you don’t have a widescreen camera, an anamorphic lens adapter can provide the necessary squeezing for 4:3 imaging chips. And, if you don’t want to spend on even that accessory, there’s always cheating.
Pretend you have a widescreen camera, and frame accordingly (use a grease pencil to mark the viewfinder, if necessary). After shooting, simply use a wipe effect to position black bars at the top and bottom of the screen.

Of course, although that’s an easy technique for creating a letterbox look, it’s not a good way to deliver images to displays that are wider. Why? Duh.

###

Wide Err

The 16:9 aspect ratio was first proposed in 1983 by Joseph Nadan of Philips as the widest that could accommodate a particular form of HDTV transmission. He also noted that it would allow widescreen set owners to watch one large 4:3 image and three smaller ones stacked at the side. Charles Rhodes of Scientific-Atlanta noted that 16:9 would allow both widescreen and normal images to be derived from a single memory by using differing pixel rates. But the biggest impetus for 16:9 came from Kerns Powers of RCA.

Powers dealt not with displays and signals but with shooting. He correctly found that 16:9 was the shape that had minimum area loss to serve any display aspect ratio from TV’s 4:3 to CinemaScope’s 2.4:1 and added many other reasons why it was a good idea.

The shape was quickly approved by committee after committee and soon became an international video standard. Unfortunately, the movie-production community largely ignored it.

Why? Minimal area loss is largely insignificant in a medium with as much resolving power as 35-mm film, but “common sides” (allowing different aspect ratios to share left and right frame edges) is important. In editing, characters enter and leave the frame at the same time no matter what the aspect ratio, and a single print can serve movie theaters with differing screen shapes.

The latter is accomplished by filling the full Academy aperture and allowing projectionists to mask off as much as they need, a technique sometimes referred to as soft matte. Powers, and the working group he chaired, didn’t know about that technique when they approved the widescreen-video aspect ratio.
“Had the SMPTE working group been aware in 1984 of the full-frame (soft mat) protection scheme,” Powers wrote in 1994, “it is by no means obvious that 16×9 would have amassed the advantages over 4×3 that persuaded the working group to make that choice.” Oops!

###

Aspects of Gravity

Is there a perfect aspect ratio? Many believe it to be the so-called Golden Ratio, referred to by mathematicians as phi, roughly 1.618:1. In the 19th century, the father of psychophysics, Gustav Fechner, found a natural preference for Golden-Ratio rectangles.

There were just two problems: Fechner actually tested for vertically oriented rectangles; it was 0.618:1 that was favored in his testing. Also, later researchers found an experimental bias in Fechner’s work. When the shapes were better shuffled, the preference for phi disappeared.

Nevertheless, research at the BBC, the Japan Broadcasting Corporation, and RCA showed a preference for widescreen over 4:3. There is much gravity to those findings.

Put another way, gravity is likely the cause of our widescreen preference for moving imagery. People moving through a frame tend to do so in a horizontal direction because gravity keeps them on the ground.
Diving and trampoline competitions could probably benefit from a vertically oriented frame. For most activities, however, the earth sucks.

###

Web Statistics