Sometimes it's impractical - or physically impossible - to get the shot you want. Maybe the scene takes place on an imaginary planet. Maybe the film is about a magical creature. Maybe the story requires action that would be too dangerous to film in real life. That's when filmmakers turn to special effects and special effects makeup.

If film is an illusion, special effects are simply one more way to achieve or enhance that illusion. Whether it's making Superman fly, allowing Fre Astaire to dance on the ceiling, or engineering a fight between Leonardo DiCaprio and one angry bear, vast teams of artists and craftspeople have devoted their working lives to making the impossible possible. 

Let's feast our eyes on the world of special effects. 

[Opening music]

We think of special effects as a recent development, but it's actually been around in some form since the earliest days of cinema. Beginning with the trick films of Georges Méliès, filmmakers have been using things like exposure, matte painting, tinting, and creative cuts to create magic on screen. And they're still at it! 

James Cameron can take us to the bottom of the sea - twice! - in The Abyss and Titanic. Ridley Scott can immerse us in the neon-drenched futuristic LA of Blade Runner. Films like Zodiac and Far from the Madding Crowd can use special effects to transport us into the past. And James Gunn can launch us into space with a quip and ship full of misfits in Guardians of the Galaxy. 

But special effects can also be used in much more subtle ways. Rather than drawing attention to themselves, these effects are meant to go undetected by the audience. Citizen Kane, for instance, is not much less fabricated than the original Star Wars. In fact, Orson Welle's classic film was a pioneer in visual effects, optically printing massive exterior shots, and featuring sophisticated old age makeup - complete with cinema's first use of contact lenses to give characters cataracts.

More recently, dramas like 2010's The Social Network used computer-generated imagery, or CGI, to complete city skylines and allow one actor, Armie Hammer, to portray twins. In Stephen Soderbergh's Oscar-winning 2001 film Traffic, CGI was even used to create tears on a character's face to enhance their emotion. In fact, the vast majority of mainstream Hollywood movies of the 21st century include at least one shot that has been altered by special effects technology.

Special effects can be broken down into several main types, which can be used on their own, or combined to produce an image that meets the needs of the film. Mechanical, or practical, effects are special effects created on set. These include physical character creation, puppetry, animatronics, and more. Think of the Cantina scene in the original Star Wars film, before Lucas went in and used computers to tinker with everything. And, no I'm still not over it. All those creatures were either puppets, animatronics, or human actors wearing prosthetic makeup or costumes.

Pyrotechnics, like fires or explosions, also fall under practical effects, along with wind, rain, mist, snow, and smoke. In some cases, even running water constitute a practical effect. Unless the film is being shot in an actual location, someone has to plumb the set if you want water to run from the faucet. 

Optical Effects are created in the camera as the film is being shot using optical instruments. A lot of these techniques require extra equipment, skills, and time, and nearly all of these effects are now easier and faster to create using computers. Optical printing involves a combination of the camera, a projector, and a special printer.

You begin by filming a live action scene, matting out the section you want to replace. This is called the "garbage matte." Then you film a shot that you'd like to use in place of the matted section. This is called a "plate." Finally, you combine the two pieces of film in an optical printer, and, voilà: special effect! 

Compositing is a technique now commonly called "blue screen" or "green screen." Originall, black screens were used. Actors would be filmed performing in front of the screen, and then the black screen would be replaced by a separately filmed background. The problem was, dark shadows also appeared black. So any shadow on the actor's clothing or face would also be replaced by the background. Not a good look.

Color cinematography and beam-splitting cameras allowed filmmakers to expose selective colors on two or three different negatives. Suddenly, it was possible to use a specific color for the screen, one that would be much easier to separate from the actors or their costumes. The first major use of blue screens in a feature film was the 1940 Technicolor spectacle The Thief of Bagdad, which won Oscars for both Cinematography and Special Effects. 

This technique continued to be refined until blue screens were the norm into the 1970s and 80s. Green screens have become more common since the advent of digital cinematography, because green is less present in human skin and hair, and digital camera are more sensitive to it. 

Filmmakers use both blue and green today, depending on the cameras being used and the costumes worn by the characters. For instance, you might not want to shoot Superman in front of a blue screen, because it could make him look like nothing but a floating head, hands, boots, undies, and a big red "S" and cape. Again, not a good look.

Optical effects can also include scale models, miniatures, and forced perspective props and sets. These techniques allowed Peter Jackson to turn full-sized human beings into hobbits and then have them interact with human characters on the same set. 

Rotoscoping is an optical effect that involves hand-tracing the subject of a shot, frame by frame, so that it can be animated or more meticulously matted into another shot.

Stop motion, sometimes called Claymation, involves shooting a model one still frame at a time, moving it slightly between each shot. The Imperal Walkers in The Empire Strikes Back were created using this technique, as well as animated films from Wallace and Gromit to The Fantastic Mr. Fox. 

Beginning in the 1970s, another weapon was added to the special effects arsenal: computer-generated imagery or "CGI." CGI covers everything from two-dimensional animation to the fully realized 3D world of something like Avatar. 

Basic rule of thumb is: if the effect is made on a computer, it's some sort of CGI. The first mainstream feature film to use CGI was the original Westworld, direct by Michael Crichton in 1973, and its sequel Futureworld in 1976. The effects themselves were quite simple - a robot's vision of our world, a 3D rendering of a spinning hand - but they actually represented an enormous step forward in the art and craft of special effects. 

Nine years later, the very first photo-realistic CGI character appeared, in the film Young Sherlock Holmes, in which a stained glass window shatters and the shards come back together to form an animated, sword-wielding knight. This moment paved the way for major advances in CGI character creation, from fantasy creatures like Gollum or Groot, to recognizably human figures like Benjamin Button, or the young Princess Leia at the end of Rogue One. 

Other aspects of CGI were equally revolutionary. Digital compositing made combining various images and image fields much quicker and easier. Keyframing, meanwhile, lets animators draw a character or object one, and then set points - or "keyframes" - to indicate how the image should move over a given amount of time. This saves artists from having to draw each frame of an image separtely. 

Now, what if your canvas as a special effects artist is actually a person? Artists who specialize in special effects makeup are trained in the same skills as traditional hair and makeup artists, and then develop more specialized expertise in creating things like injuries, old age, deformities, and the creation of monsters, aliens, and other creatures.

One of the first filmmakers to excel at this kind of special effects makeup was the actor Lon Chaney, Sr. Nicknamed "The Man of a Thousand Faces" for his ability to transform into other characters, he developed his own makeup techniques to star in Silent Era horror classics like 1923's The Hunchback of Notre Dame and Rupert Julian's adaptation of The Phantom of the Opera. 

In the early days, major film studios had their own in-house effects teams. Then during the 1960s and 70s, the studios scaled back, and those teams set up their own special effects houses which were then hired by the studios for specific projects. Today, some of the most famous brand-names in the business include Industrial Light and Magic, founded in 1975 by George Lucas; Digital Domain, created in 1993 by filmmaker James Cameron, along with master creature creator Stan Winston and digital effects guru Scott Ross; and Peter Jackson's WETA Digital, which has created the effects-heavy drama Heavenly Creatures, most of the Lord of the Rings saga, and Avatar, among others. 

Now, whether it's in-house or not, the special effects team is usually overseen by a visual effects supervisor. Their job is to ensure that the effects fit the vision of the director and the needs of the film, and that the effects are completed on time and on budget.

In order to accomplish this, they assemble and work with a variety of special effects artists, from digital matte painters and compositors, to roto artists who specialize in rotoscoping, and lighting technical directors who work as gaffers in the digital space, making sure the director, color, intensity, and mood of the lighting matches the rest of the film. 

Pre-vis - or pre-visualization artists help filmmakers anticipate what an effect look like when the film is complete, and concept artists use illustrations to help filmmakers design effects, creatures, and environments. Other artists specialize in rendering, animation, weather design, enhancing explosions, combining all the elements into a finished effect, and on and on. 

Special effects is an ever-expanding field, as new technologies emerge to make innovative effects possible. If you've ever watched the credits on an effects-heavy film, you know they list hundreds of names under special effects. All those artists spend their days working to make the impossible possible, to wow us with their imagery, and to enhance the illusion of the reality that is a film.

Today, we talked about the earliest days of special effects, from the silent trick films of Méliès to the subtle work in Citizen Kane. We broke down some of the techniques used to create special effects before computers made it all so much faster and easier. And we looked at a few of the biggest special effects companies and just some of the jobs available to special effects artists working in film today. And next time, we'll talk about who puts all of these filmed elements together to make the actual movie: the editor.

Crash Course Film Production is produced in association with PBS Digital Studios. You can head over to their channel, check out a playlist of their latest shows, like Physics Girl, The Art Assignment, and It's Okay to Be Smart. This episode of Crash Course was filmed in the Dr. Cheryl C. Kinney Crash Course Studio with the help of these nice people. And our amazing graphics team is Thought Cafe.

[Theme music]