Elmer's Guide to Theatrical Film Formats
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Hollywood Films Before the 1950s
The vast majority of Hollywood movies have been made in a 35mm format. This 35mm film is the same width as the 35mm film used in still cameras. But, unlike the film you use in your still camera, motion picture film is fed through cameras (and projectors) vertically, at a rate of 90 feet per minute. So, if you do the math, you'll discover that a typical, two-hour movie is 35mm wide and just over two miles long! Regular, 35mm motion picture film uses 4 sprocket holes or "perforations" per frame. There are 16 frames per foot of film and the film passes through the cameras (and projectors) at 24 frames per second.
The sample on the left shows a typical clip of what Hollwood films looked like before the 1950s. The frames in this sample have a 4 by 3 aspect ratio. (The term "Aspect Ratio" refers to the width-to-height ratio of a given image. The old, standard 4:3 aspect ratio is also refered to as a 1.33:1 aspect ratio. If you do the division, you'll see that these numbers represent the same ratio.) All of your favorite, old, classic films were shot in this format. You'll notice that, on the left side of the film frame, an "optical" soundtrack is included on the film (We'll have more to say about that later). The sample on the right shows how these images would look on television. As you can see, television uses the same 4 by 3 aspect ratio as old, Hollywood films, so the image broadcast on television would be virtually identical to the original, film version.
In the 1950s, Hollywood studios figured that television posed a serious threat to the film industry, so they were anxious to exploit the features of film which television could not provide, including stereo sound, color images, 3-D and wide screen processes. Some of Hollywood's 1950s experiments were just gimmicks which didn't last, but others have endured, including those wide screen processes.
The above image has an aspect ratio of 2.35:1, which is the same aspect ratio as the CinemaScope process. CinemaScope was one of the wide screen processes of the 1950s which, in concept, has endured to this day. The original CinemaScope lenses were made by Bausch and Lomb. These lenses were "anamorphic" and were designed to distort the image. The idea was to take a wide image and "squeeze" it horizontally so that it would fit in a square frame, like the one below.
This is how the image actually appeared on the film. Then, another "anamorphic" lens on the projector was designed to stretch the image back to its original, wide aspect ratio in the theatre. Soon, other companies developed their own anamorphic lenses and there were several format names, but all those processes operated the same way and were usually compatible with each other. Eventually, Panavision lenses were regarded as the best anamorphic lenses made and the CinemaScope name died out. But the concept behind CinemaScope remains with us in the equipment manufactured by other companies.
Audiences soon showed that they enjoyed the wide screen of CinemaScope and studios enjoyed having something which television couldn't imitate. But not every studio or theatre was ready to make all the costly equipment upgrades necessary to use this new process all the time. Instead, the studios adopted a new standard for the 35mm films which were being shot with normal lenses. They eventually agreed on a wider frame which fell somewhere between the old 4 by 3 frame and the new, 2.35:1 frame. Specifically, they went with an aspect ratio of 1.85:1.
In the sample on the left, you'll see how this new aspect ratio looked on film. As you can see, it actually uses less area on the film to create the wide image than was used for the 4 by 3 image. This means a slight loss of detail in the image. But, generally, this was seen as a small sacrifice and, as film stocks improved, the loss of detail was really a moot issue. Quite simply, the ability to use a wider frame outweighed any losses from using a smaller image area. But these new, wide standards meant that none of the new films could be easily shown on television. As you can see from the sample on the right, some of that 1.85:1 frame would have to be lost for that clip to fit into a 4 by 3 frame. The loss would be even more significant when a 2.35:1 image was transfered to television.
The above image is, again, a 2.35:1 image. The first directors to use CinemaScope went out of their way to exploit the wide frame, giving us shots like this which are difficult to show on TV. But there were a few, simple methods for showing these in the more narrow, television frame.
 | Here’s the most common way that wide images are shown on TV. In this sample, we've merely cut off one side of the frame. Yes, we've lost one of the guys in the shot, but if you'd never seen the original, then this version doesn't look so bad. In some cases, the video version will turn the original shot into two shots. At some point during the shot, the person preparing the transfer may “cut” to the other side of the original image.
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 | In this sample, we’ve simply picked a spot in the middle of the original frame. Now we can tell that there are two people in the shot, but the framing is very awkward. At some point during the shot, the person doing the video transfer may decide to pan across the original frame in order to show more of the original image. But these added pans can also be very awkward because they look too “mechanical.”
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 | The sample on the left shows the least common solution to the problem of showing wide images on TV. In this case, we've stayed with the uncorrected, "squeezed" image of the original negative. Yes, you can see all of what was in the original frame but hey! These guys aren't really that skinny!
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These methods of putting widescreen images onto television are refered to as "Pan and Scan" transfers of the original image. Today, when films are transfered to video in this manner, the film usually starts with a title screen which informs the viewer that the film has been "modified from the original version and has been formatted to fit the TV screen.” The vast majority of films sold on home video are pan and scan versions. But there is a growing number of home video enthusiasts who now insist on widescreen or “letterbox” versions of their favorite films because they prefer to see the entire, theatrical image.
 | In this sample, we see the entire theatrical image within the narrow, television frame. Of course, this leaves a lot of wasted image area on the TV screen, but this method of showing wide screen movies on home video is prefered by many film fans, especially when the viewer is using any sort of big-screen TV monitor.
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When Hollywood films are made, the soundtrack is not recorded onto the original negative. Sound engineers go through many complicated steps to create rich, multi-layered, multi-channel soundtracks which are then added to the film after the editing process is complete. Therefor, there’s no need to leave space on the negative for a soundtrack. Film technicians have invented a process known as “Super 35" which uses the space normally left open for the soundtrack. Then the full-frame image can be cropped to a 2.35:1 image for the final, theatrical version of the film.
 | Here is a sample of what Super 35 frames looks like on the original film. Notice that there is no space made available on this film for a soundtrack.
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 | In this sample, we see the area of the Super 35 frame which will be used for the final, theatrical version. This process creates a frame with a 2.35:1 aspect ratio just like the CinemaScope processes but without having to use anamorphic lenses on the camera.
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 | Finally, in this sample, we see the way this image will appear on the final, "release print" which is actually shown in theatres. Notice that the image has been squeezed so that the theatre can use standard, anamorphic lenses. Also, the soundtrack has been added to this version of the film. |
The use of Super 35 offers some new options for filmmakers. They can have an attractive, wide screen aspect ratio in the theatre and then, for the video release of the same film, they can go back to the original aspect ratio of the negative. Often, when a film is shot in a Super 35 process, the home video release will be available in both a standard, 4:3 version and a 2.35:1 letterbox version, giving consumers a choice of seeing more than what they saw in the theatre or seeing the original, theatrical images. However, the cinematographers I've spoken to will admit that it's impossible to compose an image for two aspect ratios and make it look right both ways. So, the idea of using Super 35 to accommodate both a theatrical and a 4:3 aspect ratio is not wise.
A disadvantage of Super 35 is that the "theatrical portion" of the negative uses a smaller image area than normal, anamorphic processes. This can cause the Super 35 images to be more grainy and “contrasty” than anamorphic images when seen in theatres.
Another one of the wide-screen formats which has endured over the years is the 70mm film format. For this format, the film is, obviously, twice as wide as 35mm film, but each frame is 5 perforations tall instead of 4. The aspect ratio of the 70mm frame is not quite as wide as an anamorphic, CinemaScope frame, falling somewhere between 2.05:1 and 2.2:1. (To most people, the difference is insignificant. It’s still a wide screen image.)
In truth, the film used in 70mm cameras is 65mm wide. The extra 5mm is added to the release print of the film and is used to carry the soundtrack. For many years, the 70mm format was the only format capable of carrying a 6-channel soundtrack (until the 1990s when 35mm digital formats became common). The 70mm soundtrack through the years was a set of magnetic “stripes” on the film which were capable of delivering the highest fidelity sound of all film formats (until digital sound came along). Throughout the 1960s, the 70mm format was used extensively for Hollywood musicals because of its spectacular, visual detail combined with its unrivaled, high fidelity sound. The 70mm format remains in use today but in very limited runs, including special venue, amusement park attractions.
 | Here’s a sample of the image we’ve been working with as it would look on 70mm film. Notice that there are magnetic, soundtrack “stripes” on either side of the image and on the outer edges of the film. |
Speaking of special venue attractions, let’s take a look at the IMAX format. This format, once again, uses 65mm film but the film runs through the cameras and projectors horizontally. And each frame is 15 perforations wide! This huge image area allows incredible visual detail. Then, when these images are projected onto screens which are typically 7 stories high, the theatrical experience is nothing short of spectacular. The cost of producing IMAX films combined with the limited number of IMAX theatres in the world has limited the format to special venues. In recent years, there have been a number of special venue IMAX 3-D films produced. If you’ve never seen one before, make it a point to go the next time you visit a city with an IMAX theatre.
What about soundtracks?
In the samples I've shown you, the soundtrack is included on the release print. A system which includes the sound on the film is called a "Single System." In a "Double System," the soundtrack is contained on a separate medium and is somehow synchronized with the picture. Synchronization is usually acheived through a "time code" which is printed on the film and also encoded into the sound medium. Special circuitry uses this time code to match the sound to the picture in perfect sync.
Dolby Digital and Sony Dynamic Digital Sound (SDDS) are each considered single system formats. Analog sound is also included on the film and is a single system. The theatrical version of the DTS Digital sound system is a double system. A time code is printed between the analog soundtrack and the image on the film. A separate DTS CD-ROM contains the digital sound. The IMAX projection system also uses double system technology for sound. Years ago, IMAX sound was carried on 1-inch wide, multi-track audio tape which ran in the projection booth. Later, the sound was carried on 3 interlocked audio CDs which provided 6-channel sound. Today, there are other digital sound formats used with IMAX in double system configurations, including DTS digital sound.
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When films are printed for theatres, they are divided into separate reels, each of which is about 20 minutes long or less. So, the average, 2-hour movie will be shipped to theatres in a six-reel set. (If the film is 2 hours and 10 minutes, for example, then it will be 7 reels long and the last reel won't be a full 20 minutes.) In today's multiplex theatres, the projectionist will splice all the reels of the feature film together into one, long piece of film (including all the trailers and logos at the beginning of the presentation). The complete film is then loaded onto platters like the ones pictured on the left. |
These automated systems allow a single projectionist to operate several projectors at once. In a normal situation, the projectionist only has to thread the projector before each screening and then simply press one button to start the system for each screening. The sound, picture and house lights will all be controlled automatically after the projectionist pushes that one button. The lights even come back on automatically at the end of the show. In theory, the projectionist could start the show and then leave the building for a couple of hours. However, the projectionist shouldn't leave because, from time to time, films do break during a screening and the projectionist needs to be close in order to repair the break in a timely manner.
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The photograph on the left shows an actual, 70mm theatrical print of Return of the Jedi just before a screening in the summer of 1983. You've never seen the film this way before! When theatres use an automated system like this, the film is taken from the middle of the roll and, after it runs through the projector, the film is rolled up anew starting in the middle of another platter. So, when the screening is finished, the film is wound up exactly as it was at the beginning. There is no need to "rewind" the film at the end. In fact, rewinding (the way you rewind things in your VCR) is impossible in a system like this. If you've ever seen a film and there was a problem and you asked the manager to rewind the film and repeat the previous 5 minutes, the manager probably said "we can't do that" or just looked confused. That's because they were using a platter system like this and, trust me, rewinding is not advisable. It's possible, but someone would have to slowly turn the platters by hand and it would probably take 20 minutes to manually rewind 5 minutes worth of film. And, if you're not extremely careful, you might damage the film. |
You may be wondering about the "old days" when projectionists used more than one projector for each screen and, during the movie, there would be a "changeover" from one projector to the other whenever there was a reel change. Yes, that really happened, but the use of multiple projectors for a single screen is rare today. Not only is it expensive to purchase and maintain two projectors (as opposed to one projector and a set of platters) but the "changeover" must be monitored by a projectionist. Therefor, a 10-screen multiplex might need 10 projectionists to monitor all the reel changes whereas, with a platter system, a single projectionist could run the entire theatre.
Before the end of each reel, a set of dots in the upper, right corner of the picture gives the projectionist a visual cue so that he can start the next projector in time. When a changeover is done properly, the start-up of the "second" projector is timed so that the instant an "old" reel ends the first frame of the "new" reel appears on the screen. Changeover systems also allow the projectionist to switch the sound monitor from one projector to the other the instant the picture changes. Many projectionists who still use changeover systems will use large reels which can hold about an hour of film each. They will splice the reels together so that a normal, 2-hour movie is in two pieces with only one changeover required. There aren't many reels large enough to hold an entire 2-hour feature and there's no need for them, since platter systems can do that job so well anyway.
Although the vast majority of projectionists today don't need the dots in the picture for changeover cues, the dots are still there on theatrcal, release prints of movies and you've probably noticed them about every 20 minutes when you watch movies. In some older, home video versions of films, the dots are also visible. But, today, when the studios produce home video versions of films, they generally use master prints which don't have the dots.
There's a great web site for Projectionists and/or anyone interested in that part of the film exhibition business. Click Here for Film-Tech.com.
Now, would you like to know more about Motion Picture Sound Formats in particular? Click Here for Elmer's Guide.
- Links to other sites on the Web
- The THX Home Page
- The Official Dolby Site
- The Official DTS Site
- The Official SDDS Site
- Film-Tech (Tons of resources for projectionists!)
© 2008