I’ve done a lot of research into this subject since we first decided to do this issue in January, but I’m hard pressed to give a more concise description of the technology than the one that effects filmmaker Zach from Fox’s On the Lot put it: “greenscreening is just basically telling the camera to replace anything it sees as green with whatever you [the director] want.”
So where exactly does the term “chromakeying” come from ? “Chroma” is the word used to describe color that a camera can record in technical terms. (As opposed to “Luma”, which is the word used to describe the light that a camera can record.) Keying is an old production term that refers to removing an object from a picture using a form of matte. So Chromakeying is simply removing any color that you designate and creating a matte in the shape of the removed color. Over these matted out areas, the keying or editing software you use shows any background you choose.
With that said, for most of our readers, that doesn’t make the actual way greenscreening or chromakeying works any less mysterious. It’s all well and good to realize that you shoot something or someone in front of a colored background that is different than your subject and you can have almost any editor or keyer delete the background. However, anyone who’s dabbled in this strangely occult field has probably discovered that their results often don’t hold a candle to the work done by ILM or TroubleMaker Studios.
When you try greenscreening and don’t get great results, it can be really tempting to just write it off as something that’s not able to be done in a believable way on a low budget. Hollywood has extremely powerful equipment, software, and a lot of money to make its movie magic, so it can be easy to believe that their advantage allows them to do what we cannot. As we were getting prepared for this issue, I looked at the most common hurdles to low budget filmmakers being able to get good quality greenscreen results.
The number one hurdle was simply a lack of readily available information on the art of greenscreening. Up until the past couple of months, the only training on greenscreening that I had been able to locate was some pretty basic work in Total Training’s Advanced After Effects series and a few powerful lessons in Andrew Kramer’s Serious Effects & Compositing. As such, I decided to find training that most people were unaware of and feature it here, as well as offering training in this magazine. Ironically, as I was in the final stages of preparation for this issue, the first book I’ve ever seen published on chromakeying was published by Elsevier: Bluescreen Compositing. And, this month, Creative Cow and Post both published a few articles on the art of Greenscreen shooting. This makes me think that a lot of us realized the need for information in this area at about the same time, which is always a good sign for everyone.
With that said, this article is designed to give you some understanding of how to recognize the limitations low budget filmmakers have in regards to their equipment and how to do your best to overcome them in production. (To help overcome the issues you will face in post, we did a shootout of six different chromakey software packages that’re available which you can read here and we have included two articles from the aforementioned Bluescreen Compositing by John Jackman, one on zMatte and one on Adobe Ultra CS3)
