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Hollywood's Secrets Revealed: Special Effects in the Movies

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Hollywood's Secrets Revealed: Special Effects in the Movies

Look inside the creation of some of special effects in the movies.

For generations, moviegoers have marveled at the magic of Hollywood's special effects. Understanding some of the techniques will help you with your own productions.

We tend to think of special effects in the movies as a recent phenomenon. But at the turn of the century - within months of the invention of the movie camera - you could see disappearing people, magical transformations and even exploding heads in the movies. Storytellers instantly appreciated film as a medium where fantasy could be brought to life. In this article, you will learn some of the best tricks used to make special effects in the movies.

Miniatures

Miniatures have been a part of special effects in the movies since the beginning. Scale models allow photographers to create anything in (or out of) this world, but they are not without problems.

One headache when using models is their motion, since gravity doesn't scale proportionately with size. To make a miniature look real, producers shoot it at high speed (called overcranking) and play the footage back in slow motion. Videographers can simulate this special effect by recording using a high speed shutter and slowing the motion down using a nonlinear program like Adobe Premiere or the Casablanca, or by playing the tape back on a high quality VCR that allows slow motion replay.

Miniature explosions, tidal waves and landslides all use the same slow-motion effect, with differing degrees of success. Water is perhaps the most difficult medium to miniaturize. Slowing down the action helps, but when the miniature is enlarged to match the live action, the droplets also become enlarged -- a dead giveaway.

An expensive way to fix this problem is to use giant miniatures. That's the route James Cameron took when filming Titanic. He used many miniatures of the ship with the largest full model at 45 feet or 1/20 scale. In the scene where the propellers of the ship stuck out of the water, he used a huge, 1/8-scale partial model of the stern and overcranked the camera by a factor of three. It made a truly impressive backdrop for the people floating in the life rafts in the foreground.

Miniatures can be combined, or composited, with live action in dozens of ways. When done well, the composited scene is hard to disbelieve. One of the oldest compositing tricks is the Shuftan process. This special effect involves strategically scraping some of the silver off a mirror, then setting the mirror in front of the camera at an angle. While the mirror reflects a miniature off to the side, the live action takes place in front of the camera, seen through the scraped area of the mirror. This works quite well. Since the mirror itself is out of focus, the edge between the miniature and the live action is blurred.

Another method is to suspend a model between the camera and the actors. This method, called the hanging miniature, is similar to a glass shot (discussed below), but it has an advantage: miniatures usually share the same lighting and shadows as the full-size set, so they blend right in. Positioning talent, mirror and camera in such a way as to create the illusion of the proper relative sizes is called "forced perspective."

Glass Painting

At the turn of the century, Norman O. Dawn was shooting a short documentary about California missions. Several of the missions he wanted to include were rather dilapidated. To spruce them up, he set up a piece of glass in front of his camera and shot through it. Where the buildings were crumbling, he hid them by painting on the glass, matching the colors and textures perfectly.

The method caught on quickly and is still a standard special effect used in the movies. To add to a set without actually constructing one, you can just build the doorway, for instance, and paint the rest of the building on glass. With the glass between the camera and the doorway, you can create any world you want.

Rear (Back) Projection

Soon after its invention, rear projection caught on as one of the most flexible ways to composite images. As time passed, the technique was improved and modified considerably.

Norman Dawn first used rear projection around 1913, but with the anemic projector bulbs available at the time, he didn't get very good results. It was not until the 1930s, when bright bulbs became available, did rear-projection come into widespread use.

The technique requires the synchronization of the camera and the projector to avoid flicker. It is imperative that the angles and perspective of the projected image not clash with the live action.

Rear projection was a beloved staple of directors like Alfred Hitchcock who used it even in the face of newer and better technologies. Hitchcock's most prominent application was to create the moving background seen through a car or train window. You can spot a poorly done rear-projection job by noting the relatively low contrast in the projected image. This is still one of the major drawbacks of the method.

Blue-screening

Developed for film as another method of compositing, the blue-screen process quickly became the most popular technique for creating unusual backgrounds. First, the actors are filmed against a blue screen. Then, with a little darkroom wizardry, the blue areas were replaced with a background screen, dropping the actors into any world the producers desired.

The same process soon applied to video and computers. With film the process is chemical, with video it is electronic and with computers it is algorithmic. Of the three realms, the algorithmic is the most flexible.

There are some problems with blue-screen. If the talent wears something blue it will become transparent, poking a hole right through the actor. You need to be very careful with the wardrobe for a blue-screen shot. This caused some consternation on the set of the movie Superman, where the blue-suited hero had a tendency to disappear altogether. To fix this niggling detail, they made a special purple Superman suit. Before compositing the final image, the suit was color-corrected back to blue.

Blood

In the good old days of black and white movies, blood (when shown at all) was just chocolate syrup. The actor put a little syrup in his hand and slapped it onto his chest for the easiest gunshot effect of all time. In the age of super-realism, that technique just won't cut it. You need "Technicolor Blood" (that's the actual trade name). It looks great, it scabs over like the real thing and, it's washable.

Blood often involves plumbing. A gushing wound requires tubing to deliver the blood. Technicians often hide the tubing behind latex appliances (porous foam rubber made to look like skin), but it is simpler to have it run behind something, out of the view of the camera. Another way is to attach the plumbing to a knife, ax or scissors. Add a tube to the unseen side of the murderous instrument and have it deliver blood as it slices, chops or stabs. A rubber bulb at the end of the tube is us>Blood often involves explosives. To simulate a gun shot with maximum grossness, technicians use a squib, which is a small electronically triggered explosive. To simulate a gunshot wound to the chest, they strap a metal plate to the actor's chest to absorb the impact of the squib. The squib is attached to a small rubber bag of fake blood. The actor dons his costume, and on cue, the technician explodes the squib and blood splats all over.

Videographers have borrowed effects like these from Hollywood for years. These are just a few of the tricks the masters use to fool the audience. Throughout movie history, directors have pushed the limits, constantly gaining an advantage over their peers. The effects are now so good that they are virtually undetectable. What will come next from the fevered brains of the F/X wizards is anyone's guess, but you can bet that videographers will be performing the same effects in their backyards in the not-so-distant future.

And Now, the Computer?

With Jurassic Park, the world of special effects changed forever. No longer content with bit parts and touch-up work, computers burst on the scene with full-blooded, snorting, sneezing dinosaurs.

How do you build a digital dino? First, using fossils for accuracy, the graphics gurus created a computerized skeleton. Then, advised by paleontologists, they programmed the muscles and wrapped digitized skin around the carcass. Finally, they computed the motion.

At that point, hundreds of networked computers went to work, calculating how the light would reflect off the dinosaurs and back at the viewer. The calculations are so complex, it could take hours for a workstation to generate a single image.

Finally, after thousands of frames had been generated, the dinosaurs were composited with the live action. The result is a stunning realism that immediately became the gold standard for effects. Although the traditional methods discussed in this article are still used, their days may be numbered---in Hollywood.

Tags:  October 1998
Scott
Anderson
Thu, 10/01/1998 - 12:00am

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