WHAT THE HECK IS ANAMORPHIC? by Dan Ramer

DVD's single most significant improvement to the NTSC video format is anamorphic widescreen capability. Knowledgeable DVD buyers demand it. When studios neglect to offer this superior video capability it becomes a source of irritation and provokes disdain within the DVD community. But there remains a vast number of people, either new to DVD or considering getting serious about home theater for the first time, who are still confused by anamorphic widescreen. The studios haven't helped. Read the backs of DVD cases and you'll find "enhanced for 16x9 televisions," "enhanced for widescreen televisions," "enhanced for 16x9," "widescreen 16x9," "16x9 anamorphic," and the terminology we prefer at DVDFILE.COM, "anamorphic widescreen." So let's try to get a clearer picture of this concept.

What Is An Aspect Ratio?

It's difficult to approach this subject without a brief discussion of aspect ratios in general. Aspect ratio is a way of expressing the proportions of a screen; it's always stated as horizontal size versus vertical size. For example, the earliest standard motion picture aspect ratio is the Academy Format of 1.37:1. You'll note that the height has been "normalized" to one. This makes other calculations easier. For example, a 50-foot wide screen in this format would be 36.5 feet high (50/36.5=1.37/1). When NTSC (National Television Standards Committee) television was introduced, the decision was made to emulate the motion picture format, but round off the proportions to whole numbers, 4:3 or 1.33:1.

Motion Picture Standard and NTSC Television Standard Aspect Ratios

As television began to erode film theater attendance, the motion picture industry counterattacked with a variety of widescreen film formats that had a greater visual impact on the audience. Years later, as DVD was being developed, two motion picture formats had evolved to dominate, 2.35:1 and 1.85:1.

Common 1.85:1 and 2.35:1 Motion Picture Aspect Ratios

 

Letterboxing presents its own set of problems. And here I must beg your patience for a necessary digression into the nature of video. Film is composed of a series of still images. Twenty-four frames are projected onto the motion picture screen each second. Each frame is a whole unit, a complete image, analogous to a 35mm slide. Video is quite different. Each visible image is created by drawing the picture with horizontal stripes called horizontal scan lines. Within an NTSC television image, there are 480 active video scan lines - horizontal scan lines - that contain picture information. (Let's ignore the issue of interlacing, it doesn't really belong in this discussion.) Each scan line has a measurable height and a measurable spacing between scan lines, so each picture is crudely divided into 480 horizontal scan lines with a small black spaces between them.

In the motion picture theater, when the aspect ratio increases from 1.85:1 to 2.35:1, the screen is made wider; black masks are pulled out of the way on either side of the projection screen. The height of the image remains the same. When a film is letterboxed in a 4:3 video frame, the full width of the film occupies the full width of the video frame. But due to the aspect ratios of widescreen film formats, the film's image doesn't fill the height of the video frame. Those areas are left black. Hence, the black bands top and bottom of the television picture.

To letterbox, some of the 480 scan lines are not used to reproduce the film's image, and therein lies the problem. As the film's aspect ratio increases, more and more of the scan lines are thrown away; they are wasted, forced to reproduce the black letterbox bars at the top and bottom of the video frame instead of reproducing picture information. This reduces the amount of detail that can be displayed. Let's consider a simple example, a black circle on a white background that occupies the full screen height on a 2.35:1 aspect ratio film frame. In pan & scan, the circle might look like this:

All 480 of the scan lines are active. The circle is reproduced as accurately as possible, with a minimum amount of "jaggies" caused by the horizontal scan lines. (In the illustration, I've exaggerated the jaggies by reducing the number of scan lines. I've also removed the "anti-aliased" edge transitions that would occur in real video. In real video, the edges would include shades of gray to soften the transition between the white background and the black foreground. This effect is attributable to the way images are scanned by the camera.)

If we wish to see the full width of this 2.35:1 film and we letterbox it, fewer scan lines will be used to represent the circle. The effect is a dramatic increase in he jaggedness of the circle. In NTSC video, only 272 of the 480 possible horizontal scan lines would be used. This is the process that has been used overwhelmingly for widescreen laserdiscs (although a few rare anamorphic widescreen laserdiscs have been produced.) So the question facing the DVD consortium was, how can we involve more of the 480 visible scan lines to improve the resolution of the image on the screen? They ultimately looked to film industry techniques for the solution.

Widescreen films are shot with either spherical or anamorphic optics. If spherical optics had been used, when you hold a film frame up to the light, a circle would appear round. An anamorphic camera lens squeezes a wide image horizontally to make it fit a standard 1.37:1 frame; hold an anamorphic film frame of a circle up to the light and it appears as an oval, tall and thin. When projected, an anamorphic projection lens optically unsqueezes (widens) the image and restores the correct aspect ratio. (You can tell if a film was shot with an anamorphic lens by observing out-of-focus points of light in the background of any scene. If the light is round, a spherical lens was used. If the light is tall and thin, an anamorphic lens was used.)

Example Of An Anamorphic Image The Circle Is Vertically Stretched (Note The Oval Shape)

Since there are 33% more scan lines in the anamorphic widescreen video image, the circle appears smoother and the spacing between the scan lines is reduced. Compare the appearance of the anamorphic widescreen simulation on the left with the letterbox simulation on the right. The only difference is that the anamorphic widescreen simulation has 33% more scan lines.

The improvement in the appearance of film on anamorphic widescreen DVD is even more dramatic. For a film shot in 1.85:1 aspect ratio, a letterbox presentation uses only 345 scan lines. The same aspect ratio in anamorphic widescreen uses 461 scan lines (or all 480 scan lines if the telecine operator chooses to throw away a tiny bit of side image and present the film as 1.78:1). Similarly, for a film shot at 2.35:1, a letterbox presentation uses only 272 scan lines. An anamorphic widescreen presentation uses 363 scan lines. The additional detail is startling on a big screen, on any screen size from 35 inches and upward the difference should be clear. And when viewing an anamorphic widescreen DVD with the aid of a line doubler, the line structure all but disappears.

There will be a significant number of you who may not as yet own a display that offers the anamorphic widescreen vertical squeeze as a standard operating feature. Until you do, here's a helpful hint. Independent of the film's aspect ratio and the number of horizontal scan lines actively displaying picture content, anamorphic widescreen requires that all 480 horizontal scan lines are squeezed vertically from the conventional aspect ratio of 1.33:1 to an aspect ratio of 1.78:1. This aspect ratio may also be expressed as 16x9 since 16 divided by 9 equals 1.78, hence we find such terms as "Enhanced for 16x9" and "16x9 Anamorphic." If you can manually adjust your display from either a service menu or with analog controls (and you feel a little adventurous), you might want to try the following. First reduce your display's picture width until the edges of the video frame are just outside the edges of your viewing area. (You've just reduced your horizontal overscan to near zero; overscan is typically delivered from the factory at a setting as high as ten percent.) Measure the width of your picture and make a note of it. Have a calculator handy. Next reduce the height of your display's picture, measure the height, and divide the measured width by the measured height.

The result should be 1.78. Repeat the height adjustment and calculation until you achieve the right result. Marking the picture height alongside the picture area with a couple of tiny pieces of semi-transparent tape will help guide you back and forth between 4:3 and 16:9. Returning to 4:3 simply requires increasing the picture height until the picture's top and bottom are just outside the top and bottom of the viewable area. Please note that applying this method on a display that was not intended to be used in this way can adversely affect your color convergence as you play with the height and width, and, depending on the manufacturer, this may violate your warranty. And most important, do not attempt any internal adjustments unless you are qualified; there are shock hazards within all television and display interiors.

Support?

This nicely segues into an issue that has discouraged some studios from fully embracing this superior video format. There are a limited number of 16:9 monitors and 4:3 monitors capable of performing the required vertical squeeze in the hands of consumers. As a result, many DVD owners are forced to use the player's hardware to convert the anamorphic widescreen images to 4:3. On inexpensive players, this is done typically by throwing away every fourth horizontal scan line. As you would expect, this could cause an even more visually annoying kind of jaggedness than 4:3 letterboxing. But several manufacturers, Sony and Pioneer to name but two, have developed more sophisticated algorithms to perform the conversion that are quite nice to view.

What we, the DVD buying community, must do is insist that all hardware manufacturers improve their conversion techniques. We must also maintain pressure on the studios, the software manufacturers, to resist the notion of dumbing-down the DVD. Purchasing anamorphic widescreen DVDs will reap dividends from a future investment in your home theater. Being forced to buy conventional widescreen letterbox DVDs will become a source of disappointment and frustration as your equipment becomes more capable. It's my hope that this situation will change rapidly as the electronics industry offers the vertical squeeze feature on more displays. One thing is certain. Surveys of DVD purchasers consistently reveal two important facts: anamorphic widescreen is very important to you; and, the overwhelming majority of you either own or will soon purchase monitors that are capable of taking advantage of the increased resolution. For example, one site survey at The Big Picture asked, "Widescreen or Standard? What's your pleasure?" Of the nearly 1700 responses, 27% reported owning a 16x9 display, and 67% reported their intent to purchase one. That's a significant 94%.

As I write this article in late December of 1999, we've seen Paramount, Fox, and Buena Vista slowly move toward support of visually superior anamorphic widescreen. Paramount seems a bit more serious; Fox and BV are somewhat tentative. Let's hope that in 2000 we'll see consistent support for anamorphic widescreen DVDs, the demise of widescreen letterbox in conventional 4:3 video, and appropriate, effective support from hardware manufacturers.