Hollywood's Secrets Revealed: 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 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."

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.

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.