How Video Formatting Works


If you've watched many movies on video, you've probably read the words, "This film has been modified from its original version." But how has it been modified? The message that appears at the beginning of video tapes isn't very specific. As it turns out, there are a number of ways video producers modify theatrical films for video release, and elements of these processes have sparked heated debates about maintaining artistic visions.

In this article, we'll examine the methods and issues involved in formatting movies for videos, DVDs and television. We'll also take a look at the history of film aspect ratios and talk a little bit about the future of video formatting. By the end of this article, you'll be able to watch movies and videos with a whole new understanding of the process of their production!

What is Video Formatting?

There are a lot of things involved in showing theatrical movies on a television because movies and television are very different mediums. Movie film is a very physical medium. It's exactly like the film in your still camera in that it records visual information with chemical reactions on special material. Video, on the other hand, stores visual information as an electronic signal that can be transmitted via radio waves, sent through coaxial cable, etc. Because of this, film and video have very different properties. For one thing, they don't split up still images the same way. Filmed movie frames must therefore be reorganized into a video format before a movie can be shown on a television.

The more controversial formatting issue is changing the shape of a movie's picture so that it fills a television screen. Video producers significantly change most movies from their original theatrical presentation because standard television screens have a different shape than standard movie pictures. A standard television has an aspect ratio, or ratio of width to height, of 4:3. Another way to express this ratio as 1.33:1. This means that a television screen is 1.33 times as wide as it is high. Theatrical movies are filmed using several different aspect ratios, almost all of which are somewhat wider than a television screen. These days, the most common U.S. theatrical aspect ratios are 2.35:1 and 1.85:1, but some movies are even wider. As you can see, while a television screen is fairly close to a square, a movie picture with a 2.35:1 aspect ratio is more than twice as wide as it is high.

Consequently, modern movies do not automatically fit standard television screens. In order to release a movie on VHS video and DVD or broadcast it on television, video and television producers have to accommodate this difference. There are a number of ways of accomplishing this, each of which we'll examine. We'll also look at why televisions and theatrical movies have different aspect ratios in the first place and explore the "widescreen vs. pan and scan" debate. But first, let's look at the first step in video formatting, turning moving pictures on film into moving pictures on video.

Frame Rate Conversion

The easiest way to convert a film to video would be to project the film and shoot it with a video camera. This would give you a copy of the movie on video tape (this is how people make illegal video copies of movies that are only playing in theaters), but the image would have a constant flicker to it. This is because film and video have a different frame rate, meaning they show a different number of still images per second.

Most feature films are projected at a rate of 24 frames per second. This means that in one second, the projector shows 24 complete still pictures in succession. This is essentially the entire process of creating the illusion of movement with film. Video formats were designed to be used on cathode ray tube televisions, which work in a completely different way than a film projector. If you've read How Television Works, then you know that a television creates still pictures line by line, with an electron beam that passes over a phosphor-coated screen, in rows from left to right, top to bottom. When television was first developed, it wasn't feasible to create a system that could "paint" all the lines in one pass over the screen, so the cathode ray tube system was modified to paint every other line in one pass and then fill in the lines in between in a second pass. This process is called interlacing, and each complete pass of the electron gun is called a field. Technology has improved to the point where we don't have to build televisions this way, but much of the rest of television broadcasting equipment has been designed around this idea, so it is fairly entrenched for the time being.

The video used in traditional television signals takes this particular form, but specific formats vary from country to country. There are three commonly used formats:

  • National Television Standards Committee (NTSC) format: Used in the United States, Canada, Japan and elsewhere
  • Phase Alternation by Line (PAL) format: Used in European countries and other parts of the world
  • Systeme Couleur Avec Memoire (SECAM) format: Mostly used in Eastern European countries

On a PAL or SECAM system, the electron beam passes over the entire screen 50 times a second, which means the television presents a complete picture 25 times a second. This is pretty close to 24 frames per second, so if you make a direct conversion showing one complete film frame in every full video frame, the movie plays pretty well, just a tiny bit faster. The main thing you might notice is that all the sound has a slightly higher pitch.

NTSC format shows about 30 frames per second (60 fields), so it is a bit trickier. Mathematically, you can't easily spread 24 frames across 30 frames. But you can divide up 60 fields so that you show only 24 frames per second, if you use a block of five video fields to show two film frames. The math is pretty simple:

  • In one second of video, there are 60 fields.
  • So, you show five fields in 1/12th of a second (60/12 = 5).
  • In one second of film, there are 24 frames.
  • So, in 1/12th of a second, you show two frames.
  • If you record only two film frames for every five fields of video, you can create a video copy of a movie that plays at the correct speed.

Of course, you can't divide five by two evenly, so formatters have to stagger it. A video copy of a movie shows frame 1 for three fields, frame 2 for two fields, frame 3 for three fields and so on. This doesn't present motion exactly as it appeared when the movie was projected (pans aren't as fluid, for example), but the movie isn't sped up at all and the soundtrack isn't affected.

But how do you split up a movie this way? This is done with a device called a telecine. There are two different types of telecine, film chains and flying spot scanners.

Film chains are the cheaper option, but they don't make as good a copy. With a film chain, you attach a special kind of shutter to a film projector and project the image through a lens and off of a mirror to a specialized video camera. The shutter is rigged so that it projects each frame for the appropriate amount of time.

The other type of telecine, the one used for higher quality video copies, does away with the projector and the shutter. Flying spot scanners run a little light on one side of the film and a little camera on the other side of the film, so they can scan each frame of film. Once a film frame is scanned, it's very easy to divide it up into different video fields.

This process works a little bit differently with DVD movies. DVDs store movies in MPEG digital format, which compresses the movie file by using the same image information from frame to frame. For a full description of how this works, check out How DVDs and DVD Players Work.

Aspect Ratios

Theatrical filmmakers have primarily used 35mm film from the very beginning of movie production, and they continue to use it to this day. This is mainly because it is the established standard. The actual aspect ratio of 35mm film is 1.33:1, the exact aspect ratio used in conventional televisions -- when television was developed, it was a logical choice to model them on the shape of films. This exact ratio was used for most silent pictures, but Hollywood changed the picture ratio slightly with the advent of talkies, to make room for an audio track. The new ratio, 1.37:1, became known as the Academy Ratio and was used for the vast majority of U.S. films until the 1950s. Most movies produced before the 1950s fit conventional television sets fairly well.

But in the 1950s, movie-makers began developing techniques to widen the aspect ratio of their movies. The primary reason for this was the increasing popularity of television; to keep people coming to the movies, Hollywood had to give people entertainment they couldn't get at home. They began making wider and wider movies, featuring spectacular panoramic cinematography. The main thing movie theaters had over television sets is that they could immerse the viewer more deeply in the world of the movie, and the best way to do this was to fill more of the audience's natural field of vision (which has more width than it does height because our eyes are positioned side by side).

In addition to the grandeur and immersing qualities of panoramic scenery shots, wider aspect ratios simply allow for more interesting artistic composition. If you go to an art museum, the vast majority of paintings you see will either be significantly wider than they are tall, a "landscape shape," or significantly taller than they are wide, for a "portrait shape." This is because a more rectangular canvas shape allows the artist to balance the elements of the painting more effectively, which creates a sense of visual harmony. Movies are the same way: A director and a cinematographer can compose shots that are much more pleasing to the eye when they use a wider aspect ratio. The shape of a television screen, which is more square-shaped, severely limits the possibilities for interesting visual compositions.

Since the 1960s, almost all major filmmakers have used a wide aspect ratio when making a theatrical movie. They still use 35mm film with a 1.37:1 aspect ratio, however, so they have to somehow impose another aspect ratio on that film. There are several ways of doing this, and the method the director chooses determines the video producer's options for modifying the film to fit a television screen.

Today, the most common methods of imposing a wide aspect ratio are:

  • Anamorphic lens
  • Hard matting
  • Soft matting

Each method has advantages and disadvantages, and directors often have a personal preference.

Anamorphic Lens

One of the most popular ways of producing a wider picture is to "squeeze" it onto the narrower film. This is accomplished with an anamorphic lens on the camera that horizontally condenses the light it takes in. On the actual film of a movie made with an anamorphic lens, all the people and things in each frame appear unnaturally tall and skinny. In the movie theater, the projectionist attaches a similar anamorphic lens to the projector to unsqueeze everything. The advantage of this format is that it uses the entire film area to record the movie picture as it will finally appear, so it doesn't sacrifice any resolution in creating a wide aspect ratio picture. This method limits the depth of focus somewhat, however, and images in the background are sometimes distorted.

Hard-Matting

A filmmaker can hard matte a film by attaching a special mask to the camera. This mask blocks off the top and the bottom of the scene in front of it so that the film is only exposed to the desired rectangular image. This is cheaper than using anamorphic lenses, and it is a good way for a director to completely control the cinematography of his picture, but, because it only uses the middle part of the available film area, it sacrifices image resolution somewhat.

Soft Matting

A filmmaker using this method simply exposes the entire area of the film but composes his picture with only the middle part of the picture in mind. The camera may show only the middle part of the film to the director and cinematographer, or it may have an outline on the entire image that indicates the borders of the desired aspect ratio. When a soft-matted film is projected, the projectionist has to mask it correctly so that only the middle part of the picture appears on the screen. If you go to a lot of movies, you've probably spotted a boom microphone creeping into a shot or seen a movie where people's heads are cut off or there appears to be too much empty space at the top of each shot. These things happen when a projectionist doesn't properly mask a soft-matted film.

Letterbox and Pan & Scan

No matter how it was filmed, the best way to present a movie on video as it was originally created is to letterbox it. This format presents the full, wide picture on the middle of the television screen, with black bars above and below it. This maintains the movie's original theatrical aspect ratio, so that you see everything the director intended you to see. Because they preserve the original cinematography of the movie, letterbox, or widescreen, videos have become more and more popular in recent years. The format is particularly common on DVDs because their increased storage capacity can hold both a letterbox version and a full-frame version, a presentation that uses the entire television screen. Also, their increased picture quality helps counteract the loss of resolution caused by shrinking the movie picture.

The problem with letterboxing is that it shrinks the viewing area of the television screen, which, if you have a small set to begin with, can make it fairly difficult to see the movie. For this reason, letterboxing is not the most popular formatting option. Most viewers are bothered by the black bars at the top and bottom of their screen more than they are bothered by the idea of not seeing the picture as it was originally filmed, so full-frame movie presentations are much more prevalent than letterbox presentations. But if you are a student of film and want to fully experience the movie as a work of art, then the letterbox format is the only way to go.

Squeezing & Cropping

Squeezing & Cropping

If a movie was filmed using an anamorphic lens, then the complete picture already exists in a 1.37:1 format and so can be shown full frame on a television without cutting much of the image. The problem, of course, is that this image is severely squeezed, so that circles appear to be eggs and everyone's face is creepily elongated. Most viewers find this distracting, to say the least, so this formatting option is not used very often. Some video producers did release movies this way when home video was just starting out, but these days, the only time you're likely to see this is at the beginning of movies, as a means of fitting wide opening credits on the screen. The more popular option in recent years has been to letterbox the opening credit sequence

Another method from the early days of home video is cropping. This term is sometimes used generally to describe cutting off part of the original theatrical picture, but it also refers to one specific formatting method. In this original cropping technique, the video formatter simply presents the middle part of the theatrical picture on video. Cropped movies frequently have rotten cinematography and can actually be hard to follow. This is because the technique blindly ignores anything that happens on the side of the screen, playing the odds that most of the important action will appear in the middle of the screen, at least in part. If a minor character only shows up on the far left side of a wide-aspect ratio shot, then he may not even show up in the cropped edition of the movie. A particularly maddening scenario is when two characters in conversation stand on either side of the picture. The viewer sees the entire conversation with only the very edge of each person's face appearing on their screen, and nothing but blank space taking up the rest of the picture. Fortunately, this technique has mostly fallen by the wayside.

Pan & Scan

Pan & Scan

The method that has mostly replaced cropping and squeezing is panning and scanning. In this process, a video technician views the movie with its original aspect ratio and decides which television-sized chunk of the movie to show at any one time. Usually, this means focusing on the elements of the picture that are most important to the plot, which is obviously a subjective decision. If you have two characters at either end of a widescreen shot, for example, the pan-and-scan operator must decide which one to show. The operator will probably show the one that is talking, or performing the more conspicuous action. A careful pan-and-scan operator will try to represent the different important aspects of a shot by "cutting" between the two halves of the screen, so that what was originally one shot becomes multiple shots. The operator can also create a pan from one side of the picture to another (hence the name of the process).

To see what you might miss when a movie scene has been panned and scanned, click several times on the left or right arrow.

If a movie was shot with an anamorphic lens or a hard matte, the two main formatting options are to letterbox the movie or pan and scan it. If the movie was shot using a soft matte, however, there is a third option.

Open Matte

We know that a filmmaker using a soft matte exposes the entire film area when shooting a movie. If 35mm film is used, this full image has an aspect ratio of 1.37:1, fairly close to television's 1.33:1 aspect ratio. One formatting solution is to leave the matte "open," making the video copy of the movie from this entire film area. The picture then fills the entire television screen and only crops a small amount from the sides of the filmed image.

The success of this method depends on how the director shot the movie. Some directors compose each shot with both the soft-matted picture and the full image in mind. When they look through the camera, they see the entire picture exposed to the film and a superimposed rectangle indicating the theatrical aspect ratio. In this case, the main thing you lose in video formatting is visual composition. So if you are mainly interested in following the plot of a movie, and not so much in cinematography, a full-frame version of a soft-matted movie will probably suit you fine. A full-frame picture of this sort doesn't cut out much visual information, so you aren't as likely to miss details or plot points as you are watching a panned and scanned version of an anamorphic or hard-matted movie.

The full-frame picture of a soft-matted movie is not always usable, however. A lot of directors will use a soft matte but completely ignore what's outside the theatrical matte. If you take a full image from this sort of movie, you might very well see boom mikes, lights and unfinished sets. Also, if the movie includes special visual effects, there's a good chance they were added only to the theatrical aspect ratio portion of the image. It might be that some shots are usable and some are not. In this case, the video formatter may choose to combine full-frame shots with panning and scanning of the soft-matted theatrical picture.

For more information on video formatting and related topics, check out the links on the next page.

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