Written by Billy Baumgartner
Although Final Cut Pro is not as powerful (and wasn’t designed to be) in the composite realm as software like Adobe After Effects, most filmmakers can achieve the basic result they desire using filters within Final Cut. This avoids messy exporting and outsourcing to the other slower programs, and saving valuable time that could be spent on Facebook.
First of all, there are a few different ways to key (read: blue screen, green screen, etc.) in final cut. They are found under Effects: Video Filters: Key. You can key based on light/dark (Luma Key) based on a simple color (Color Key) or a range of color (Chroma Key), or using a computer-determined combination of the two (Primatte RT).
You can even key something based on the differences between one frame and the next (Difference Matte). Essentially, keying means to get rid of a certain aspect of the frame to make it transparent. If there is no layer below it, it will appear black.
I will be teaching you Chroma Key, which is arguably the most versatile of the filters. Chroma key contains three image controls, three sliders, and three buttons.
The top image control (the rainbow) is the color that will be removed from the image. It can be adjusted manually by dragging the two sloped lines in and out, or dragging the color itself from side to side. If you use the eyedropper tool on the right, you can select a color in the frame of the video itself to key out. The “Sat” slider adjusts the range of saturation of the color. If it is bright green, for example, you want your slider towards the right. If it is a very pale or pastel green, you want the window to contain the area to the left. The “Luma” slider determines the brightness of the color. A color with lots of white will be towards the right (pastel) and lots of black (darker) will be toward the left. To key out all greens universally, make the saturation and luma windows almost as big as they can be. The edge thin slider is a way to slightly compress or expand your selection. Softening makes the line between colors softer for a smoother transition. Enhance adds a slightly colored halo around the key image to make it appear clearer. The trapezoid button inverts your selection, keeping everything that had originally been keyed out. Happy keying!