An Introduction to Using Green Screen Effect In Film or Video
Green Screen (or blue screen) is a remarkably common film and video production technique that enhances almost every movie and television show you watch. Take a look at this 2:43 video from YouTube showing before and after shots with the effect.
Green screen is a bit of a slang term that actually means chroma key. Chroma key is a special effects process that allows filmmakers to alter the background of their shot and use whatever they want instead of what is actually there.
When filming, actors are really in front of a solid blue or green background. Then in editing, the green (or blue) is removed and replaced with other images. Chroma means color. Chroma key can actually be done on a technical level with any color, but blue and green are common because they are opposite skin tones.
Putting two images together in photography or videography is called making a composite. There are lots of ways to make a composite, but chroma key is one of the most commonly used today. Many movies today rely heavily on the effect to create whatever illusion they wish.
Next time you plop down in your favorite easy chair to stare at the tube, pay close attention to backgrounds, hairlines, and shadows. That’s where you’ll see the telltale signs of green screen. Maybe.
If it’s not done 100% right, you’ll see green tinges and uneven mixing. That sort of mistake is rampant in cheap online videos, but of course in a big budget TV show or movie there will be no green tinges. Green screen done right will look completely and totally real, even though it’s totally fake.
Watch the video above and see if you realized those scenes were done using chroma key.
GREEN SCREEN FOOLS EVEN TRAINED EYES
If you’re like most people, you are completely fooled by the wizardry of green screen. You probably think you’re looking at shows shot on location with real backgrounds and not stage props.
So sorry to inform you that you’re wrong.
Don’t take it personally. Green screen is meant to fool!
Watching the video at the top of this page will remove any doubt about how often you are fooled by green screen and fascinate anyone familiar with these popular TV shows and movies.
As you’ll see in the video, often it is just a portion of the shot that is filled in with green screen backgrounds, but sometimes every single pixel of the shot, not including the actors themselves, is green screen.
WHY IS GREEN SCREEN TECHNIQUE SO COMMON?
Lots of reasons. Green screen saves money and enhances creative potential.
Movies from the Marvel Universe would be impossible to produce without green screen. Ugly Betty would just be cheaper to produce, but that’s reason enough.
Even if the background you desire is not another planet, green screen simply makes life easier for the filmmaker. It’s so much easier to create video in a studio where you have total control over the lights, sounds, and people present. Do you really want that airplane flying overhead interfering with your sound? Do you want to take a video crew out where curious onlookers will stand there gawking, calling out, and might even try to get into the shot, so they can wave at their moms?
Sounds like a pain to me. (If the project and budget are big enough, you can control the bystanders, but if you are a small operation, you can not. As a TV news person, I had people jumping in front of my camera constantly.)
So instead of shooting on location out in the uncontrollable elements, have your actors in a studio with dark green-screen pillars that will later be replaced with images of the actual pillars of the actual Capitol building where this scene is supposed to take place. You can see the exact scenario in the video at the top of the page.
Even if you’re not doing such a massive project, but rather want to do something more modest like sell skiing jackets, green screen can transport your models to the slopes without having to pay for a crew to travel outside the studio. In other words, even mom and pop video producers can use green screen to great effect. Green screen is one of the truly “magical” things about digital video production. You can locate your video anywhere in the universe if you use green screen technique.
GOOD LIGHTING IS CRITICAL TO REALISTIC-LOOKING GREEN SCREEN
To get the best results with chroma key, you need to start with the best quality elements and then run them through a good video editing system. (Or live video switching system)
For the low-budget production, the best advice is brightly and evenly lit shots, with good backlight for your actors. That helps them stand out visually from the background, which aids in making the green screen effect more realistic looking. You want the background light to be as even as possible over an evenly-colored green background. Shadows on the background create pockets of darker color and that will make getting a good mix difficult. Folds and wrinkles in your cloth can also cause the color to appear uneven.
Green screen is a remarkably effective and common video special effect. With the proper equipment and lighting, green screen will appear incredibly realistic. I dare anyone to examine the video footage posted on this page and find the typical markers of green screen. Nope, you can not see those tell-tale green shadows or outlines, so I swear these shots look quite real, even projected onto a large screen.
ADDITIONAL INFO ON GREEN SCREEN
After posting this last night, I heard from a reader, Andre Campbell, who works in the midst of it all in Los Angeles. I wanted to share his tips with everyone since he works in the film industry and works on the very shows you watch.
Green Screen tips from Andre:
Get your background first, then you light your scene according to how the background is lit, and not the other way around.
Another reason it’s done is for safety. Movies include a lot of daring and dangerous stunts, but using chroma key makes a bridge five feet off the ground looks like it is a 105 feet off the ground. Safer environment in and around for the crew.
One of the sitcoms I worked on last year, used a silver drop as opposed to a green screen to key out. It was a smaller setup, a person at a desk, light emitted from around the camera lens. (Any color can be used, it does not have to be green. Using blue is quite common, too.)
The ‘x’ markings you see on the green screen are there for tracking. Most times, the green screen is out of focus, (for reasons of depth of field). This makes it difficult for the computer to latch onto something for tracking. The ‘x’ markings show up better in the out of focus background.
Talk about being fooled. I was working on Dirty Sexy Money, in the Paramount back-lot. The show was based in NYC, but we never went to NYC. We would see the show the week before it aired as a full crew. Now, I’ve been there and seen every scene as it was shot. This scene came up, and I did not recognize where we were. It was a Green Screen shot, after seeing it again, then I said, “Oh, they fooled me!”
When it comes to people waving at us in the street, we can pretty much lock down the streets we shoot on. In L.A. we have off duty or retired cops working with us. They are in full attire with gun and motors. (motorcycles) They help with controlling street traffic and ride along on tow shots.
If people ask why there are only some shots with just a piece of green, and you can still see things, it is because they key out the green then garbage matte out the rest.
Also, when we have (sorry had-we got canceled) 100 extras (Paramount back lot of D.S.M show) and we are going to do a green screen shot, we have to check the extra’s clothing, making sure they have on colors that will have no problems when they cross the Green Screen.
Just a thought and my two cents.
Thanks for sharing, Andre. 🙂
FOOD FOR THOUGHT
- True or False? Green screen is an informal term for a process known as chroma key. Chroma means color, so chroma key allows the filmmaker to remove any single color and replace it with some other visual.
- In your own words, give three reasons why chroma key is so commonly used in TV and movies.
- Although you’ll never see them in a high budget film, what are the tell-tale signs that chroma key has been used?