The Art of Compositing
by L'ÉluDesMontagnesInterditesSemantDesArbresSurSonPassage on March 21, 2017 - 4:02pm
The Art of Compositing
These days more than ever, television is everywhere; movies, web series, Netflix and even more software rule the market. But how does a movie get all the magic? How did the magician behind the camera transform the image to create a whole new world full of stories and adventures? All of these are possible with the right tools and a compositing workflow, which is the pipeline who lead to the final product. The process is long, but amazing. Learn what an alpha channel is, keying and a Matte Key is.
First of all, to create and transform the images took by the production team, the essential is to use a powerful and reliable software. Composition demanded a lot of energy and software; Nuke, Da Vinci, Flame are some of the Titans in the domain. These programs allow the compositor to work better and faster. Once the software is chosen, the real job can begin. Before starting, it is important to understand the basics. Each image has three layers; the red, blue and green. Each of them is called a channel. There is too the RGB channel (in other words, the result people will see), the Alpha channel (what is keeping in the frame and what will be invisible) and finally, the Matte Key (this is an effect layer, it will be explained later). All together, these three forms the final result a broadcaster will put on TV. To begin the composition workflow, the compositor will start by keying the green or blue screen in the shoots. This step is simple; with a tool called Chroma Key, the compositor will choose the color he wanted to key. Automatically, the software will erase this color everywhere; it can detect it. This is why most of the screens are green fluorescent, because this is not a natural color. One done, it is possible to replace the now invisible green screen with another element; a spacecraft for example! The keying is over and the environment is now all made up with the same process. Now, the compositor will work the alpha channel to add elements in the shots. The alpha is an invisible layer for the human eye in normal time, but with certain software, it can be seen. With this channel, everything will be black or white, no middle. When there is the black, it means that this element is not going to be seen in the final result. The white is the opposite. With that system, the compositor can add an army of robots behind the protagonist, put a grenade near him, and so on. Finally, with a Matte Key, he can put pre-conceive effects in the frame. A Matte Key is all made of transparency except the VFX objects. VFX is the shortcut for Video special effects.
In brief, this is only a quick view of the post-production world, but for a compositor, the workflow goes like this; keying the green or blue screen, add elements in the environment with an alpha channel and then, put the final elements with a Matte Key. After that, the compositor give his work to the color grader, who is going to color grade the shots and give this product to the editor who will put the last magic in the sequences to create a movie.