Chromakey Green Screen Help page for use with our Virtual Studio Sets and other backgrounds.

If you haven't used a Chroma Key green or blue screen studio before it may seem like it's a daunting or expensive set up. Really though it's not, and I hope to show how you can get up and running with the minimum of fuss and without paying too much money. This help page and the images below should shed some light if you've never used chromakey before.

So how does Chromakey work?
It's a process where a designated bright color that's on your footage is removed using your edit software which reveals the virtual background underneath and creates the look of a real studio.

Firstly why is it always green or blue? Well these colors don't really exist in skin tones (unless you're sick!) and so you will stand out more and there's less chance of you or your subject's skin bleeding through into the green. Any areas that are close to the chosen chromakey hue will disappear in post production so you need to ensure your subject isn't wearing similar shades of color to your chromakey cloth. The debate as to technically which is the best color, blue or green, for chromakey rages on but ultimately most videographers choose green as it's more likely the talent will be wearing blue or near-blue clothing over bright green.

So firstly you'll need a chromakey backdrop. This usually consists of a green or blue screen which is lit by two or three dedicated lights - as shown on the image to the left.

You can buy green cloth (any bright matte green cloth will do - you don't need special chromakey cloth) from most studio suppliers and you can also buy a framework to hang it on. Alternatively you can mount it to a wall or even just paint the wall itself green.

The most important factor to get the best key is to ensure the green area is brightly and uniformly lit. This means the cloth itself needs dedicated lighting. It doesn't have to be expensive and I've seen Home Depot work lights used for this purpose. Of course the better the lighting the better the key.

In terms of size, ideally you'll need a green area of at least 10' wide and 8' tall. You will need to put some cloth on the floor if you intend to have your talent in a full body shot.

Once you have a chromakey set up and nicely lit you should add your talent to the set.

If you want you can also add a real desk too. Make sure that the surface of the desk is not reflecting the green that's in the background as the top of the desk might disappear if it does.

For the purposes of our sample we're going to add a virtual desk in post production later.

Once your talent is positioned you should see a nice uniformed green behind him through the camera's lens.

Do make sure your talent isn't wearing any colors close to the chromakey cloth's color. Even a multi-colored tie can sometimes cause problems.

Ideally the clothing should be on the opposite end of the spectrum from the chromakey cloth color. So we're using a fairly neutral gray suit and tie.

The final step is to light your subject.

We've added three lights to the image on the left. Two of the lights are pointed either side of our subject and one is above acting as a hair light. Note that these lights should ONLY light up your subject and should not interfere with the lighting that you have already put in place on the green screen.

Position your talent's lights so that no shadows are cast onto the green screen.

It may take some fine tuning and tweaking to achieve a nice balance between the lighting on the green cloth and the lighting on your subject. Do remember that it doesn't have to be perfect but the better lit everything is, the more realistic the final output will be.

You can now film your subject's performance and transfer then the footage to your computer for editing.

If you prefer you can use a live video vision mixer to key out the green in real time and you should talk to your supplier about the costs and pros and cons of live chroma keying.

So once you have your talent against chromakey cloth you can use your edit software such as Adobe Premiere, Sony Vegas Video, Avid, Pinnacle etc to easily remove the green screen background and thus reveal the virtual background.

This is very easy to do and your edit software will have fine-tuning controls to allow you to obtain the most realistic key based on your set up and footage.

In the example to the left we used a Virtual Studio Set from our Virtual Studio Sets range of products and also used a virtual desk from the Virtual Studio Sets Construction Kit both of which are available on our website.

See links below :

Virtual Studio Sets Volumes 1 - 4

Virtual Studio Sets Construction Kit

To see how realistic this kind of set up can look please view the video below which was created by one of our customers. Here we see the above techniques used in conjunction with one of our animated Virtual Studio Sets which simply and easily creates quite a convincing look.

In summation, once you have good lighting of both the green screen and the talent and established a nice set up it's usually very easy to film your talent against the chromakey cloth and the result is a great looking key every time.

Some tips to remember :

* You must have good, bright uniformed lighting on your chroma key cloth *

* Make sure your talent isn't wearing clothes with similar colors to your backdrop color *

* Your talent must be separately well lit using dedicated lighting *

* There shouldn't be any shadows from your talent (or desk) cast onto the chromakey green screen *

Follow these simple rules and your chromakey virtual productions should be easy and fun.
Good luck!

If you have any questions or comments I'd love to hear them - please email me vynny@zkad.com

All other enquiries to general@zkad.com