A Beginners Green Screen Tutorial - Chromakey

Beginners Green Screen Tutorial: In case anyone here doesn't know what green screen (or chromakey to give it it's technical name) is, it is a technique for shooting an actor or presenter against a green background, and then later replacing the green background with a video, animation or image during the video editing stage.

Why this colour green? In theory, any colour can be used, but this colour green (and blue) is the least like the colour of human skin tones (Any similar colour on the foreground subject or presenter to the chromakey green back-drop colour will also show the video or image added in the editing stage).

It is used widely in Hollywood blockbusters and on TV shows to create sets and backgrounds that would be too costly or even impossible to build. Some movies, like 'Sin City' and '300' were shot entirely using this technique (Film makers actually use a blue screen as it better suited for that medium).

The weather person on TV performs in front of a green screen, pointing to the large map behind them. They are actually pointing at a blank wall, and looking at the image you see on the TV through a monitor (Which is why you often see them looking to the side off screen, when pointing at the map, to make sure their hands are in the right place).

Chromakey is actually quite easy to do. However, it is not easy to do well.

There is a lot of very poor chromakey videos out there, and as we say in my industry "Poor video is worse than no video at all" (You'll hear me say that a lot).

This picture shows the most common error of a 'green' edge around the subject or presenter, caused by poor lighting, back-drop and chromakey editing skills.

So if you plan to use this effect in your videos, make sure you follow this green screen tutorial, use the right equipment and take your time to do it well, because bad chromakey does not look professional, and you don't want to give your viewers or visitors the wrong impression.

Green Screen Tutorial - Part 1

The first thing you need to have is a green background, and there are several ways to achieve this.

The best (and most expensive) option is to buy a green screen cloth or 'pop up' type back drop. For this option, you will also need to get a frame to hang them on (although the 'pop up' type green screen can be lent against a wall).

You can also paint a wall with special 'chromakey' green paint and shoot your video in front of that, but make sure you use matte paint, as you don't want a shiny surface that will reflect lights etc.

The cheapest way to create a green screen is to buy large sheets of green card and stick them together on a wall.

I recommend using a proper chromakey cloth or a 'pop up' back-drop if you want the best results.

Green Screen Tutorial - Part 2

The next thing you will need is the one thing most people tend to forget and try to do without. And it always results in very poor results.

The correct video lighting. Lighting set up for videos is the most critical aspect to achieving success. Watch my video lighting tips tutorial to understand get this right. You will need at least three light sources, preferably softboxes or 'umbrella' reflector lights. Two of the lights will be on the green screen (One either side at 45 degrees facing the back-drop), and one will be on your subject or presenter directly behind the camcorder (Ideally two lights for this as well, but you can get away with just using the one).

The presenter needs to be at least three feet from the back-drop, so they do not cast any shadow onto the chromakey background (Shadows and creases in the back-drop will make it harder to get a good chromakey effect when we start using the video editing software later on).

So the trick to great chromakey is to fill the back-drop with soft even light that is twice as bright as the light on the foreground object or presenter and avoid any shadows (or creases) on the back-drop.

Green Screen Tutorial - Part 3

Your are now ready to start shooting, but the last very important thing to remember is NOT to wear anything that is similar in colour to the green back-drop.

If you do, when you add the chromakey effect in your video editing software later, the background video or image you add will be seen on that item of clothing as well.

This can be used to good effect, if you want something to disappear for instance, just cover it with another piece of green cloth, and the background image will appear on it making it seem like it has just disappeared.

This is where I add a note of caution to this green screen tutorial. If all this sounds like a bit of fun (and it is!) and something you'd like to play around with, then by all means go ahead.

But there is the danger of using chromakey just because it seems cool to do, and the results can often look very poor and gimmicky.

A recent trend in video is to use a pure white screen background. A white screen can be accomplished with the use of a green chromakey cloth or use of a white screen background. With a green cloth, your video editing software can be used to create the white background. If you want to create full body shots with an infinite white background, you'll need a large area that is painted white and lots of lighting. A large angled panel to transition from the floor to wall will make the background look like infinite white. You'll need lighting on the floor as well as the upper body. Lots of lights are needed to eliminate shadows.

Chromakey is very hard to do really well, and I recommend just using plain coloured back drops (black, white etc.) or a simple background set (Like a desk, computer and plant for example) for most videos, as they look much more professional and don't require as much technical input as chromakey.

You only require two lights for a set or plain back-drops, and the video editing doesn't require any special techniques or software.

Having said all that, if you follow the main points in this green screen tutorial, it is a lot of fun, and if done properly, it looks great and can make your videos really stand out from the crowd.

The trouble is most green screen videos are done poorly and stand out for all the wrong reasons, so do lots of practise before letting your videos go public ;-)