Updated: Jul 24, 2020
WHAT IS A GREEN SCREEN?
The green screen's technical name is called 'Chroma-Keying' and is a technology that's been around since the 19th century. Put simply; it's a way of putting one video on top of another using a green screen. One image is placed on the green screen, and the other is positioned in front of it. The color green was chosen, as this was the least commonly worn color by TV and movie personalities at that time. However, did you know that chroma keying can in fact be done using any color?
Hollywood has become famous for using green-screen effects in its top blockbuster movies. Still, as technology has developed and become more affordable, chroma-keying has become a commonly used tool used by amateur filmmakers, YouTubers, and now, the online English teacher.
Why use a green screen for online teaching?
Many online ESL companies encourage their teachers to use green screens as a way of enhancing their online English lessons. Although those unfamiliar with the technology can find getting started a little intimidating, the learning curve is quite small, and there is no reason why anyone shouldn't be able to master the art of the green screen.
There are also considerable benefits to using a green screen as part of your online lesson. A green screen can help to keep students engaged and focused on the topic at hand, most notably those younger students who are prone to losing focus more quickly. We all know that students need visual aids to help give context and meaning to the new language taught, and a green screen can take those visual aids to a whole new level.
You won't need to hold your phone or flashcards up to the screen because you can easily illustrate visual concepts using the green screen. Go on a virtual tour of the jungle, visit a supermarket or go for a virtual dinner together at a restaurant. The possibilities are endless and only limited by your imagination and lesson topic.
If you don't have a green cloth or the budget to invest in one, other green materials can also work. But, it's best to avoid plastic-based materials or any other materials that will reflect light. ts serve a purpose towards hitting your lesson goals.
What do I need to get started?
1. A Green Screen
Although the green screen seems like some Hogwarts magic, it is, in fact, just a green cloth, and you can use any green cloth big enough to cover the area you want chroma keyed during class. A beginner green screen kit can be purchased for around $75.00 on Amazon here and is worth investing in as it can be tricky to correctly hang a green screen without stands to hang it from. If you didn't want to invest in a full kit, however, then the green cloth itself can be picked up for as little as $10.00 here. If trying to hang a green screen without a proper stand then investing in some clamps can make hanging that screen a lot easier (trust me). Clamps are very cheap and can also be found on Amazon here.
If you don't have a green cloth or the budget in invest in one, other green materials can also work. But, it's best to avoid plastic-based materials or any other materials that will reflect light.
Lighting is crucial. The better the light, the more contrast there will be between you and the green screen. Having good contrast keeps the color on your clothing and any props separate from the background. The fewer shadows you have, the better, so for the best results, you should have two light sources. One for the green screen and one for the subject you're filming.
Even when teaching without a green screen, good lighting is certainly worth the investment. You can keep lighting simple if you're on a budget by filming next to a window or by using a desktop lamp. But, if you do want to invest in something a little more professional, then a ring light or a softbox will do the trick. Ring lights can be picked up for as little as $30.00 here, and are incredibly easy to set up. A softbox starter kit (with two lights) is sold for as little as $55.00 here and although they tend to be more expensive than a ring light, they are far more effective when lighting a green screen.
You will, of course, need software that enables you to use the green screen during class. Luckily, many online teaching platforms offer green screen support, for example, Zoom.
Zoom does have a default setting that enables teachers to use their green-screen backgrounds. Go to your desktop client on the Zoom homepage, click on settings (the wheel at the top right-hand corner) and select "virtual background" from the options menu on the left. From there, you can choose from a list of provided backgrounds, or you can choose your own by clicking on the '+' button.
How Do I Set it up?
1. The Easy Part
First, hang up your magical green cloth as tightly as possible. You don't want any creases in the fabric, as this will affect how it looks on screen. If you have purchased your green-screen online, then most likely it came with some stands, a pole, and some clamps. Use the clamps to hang the screen as tightly as possible.
2. The Hard Part
Next, you need to set up the lighting, and you can do this in two steps;
Step one, lighting the green screen. For good chroma keying, you must have even lighting across the green screen. For the best results, using a diffuser (a fancy name for a white cloth that hangs in front of the light) helps to spread the light more evenly across. If you have purchased a softbox set online, then it's likely it came with attachable one. However, if you are working with what materials you have at home, any thin, white cloth hung in front of the lights you are using will do the trick. For the best results, position your green screen lights behind your subject.
Step 2, lighting your subject (you). When lighting your subject, you want to make sure that your light isn't interfering with the green screen. One common problem is that as soon as you light your subject, you cast a shadow on the green screen. Once again, using a diffuser can help prevent this, but you can also solve this problem by creating some distance between your subject and the green screen itself.
What Images Should I Use?
For the best results, HD images will produce a clear picture, especially if your class is being projected onto a larger screen. Try to use images that are not only high quality, but that is also clear and to the point. If your image is too busy, your students won't know what you want them to focus on, and it can become a distraction. Of course, you also want to be sure that your images are appropriate for both the age group and the culture of your students.
So, although green screens might not be for everyone, they can certainly be a valuable resource for the online ESL teacher. Now that you know the (not so) magical tricks, I hope that these tips will give you the confidence to try using a green screen in your next class.
For fully accredited TEFL courses, check out i-to-i for a range of TEFL certificates
For teaching opportunities around the world, check the i-to-i jobs board here