Practice by downloading free green screen footage and tweaking each slider while watching the Screen Matte. In 30 minutes of experimentation, you'll understand the effect better than reading 10 guides.
1. What is Keylight 1.2? Keylight 1.2 is a professional chroma keying (green screen/blue screen) plugin developed by The Foundry, included with Adobe After Effects. It uses a sophisticated color difference algorithm to create clean, transparent backgrounds from uniformly colored footage. keylight 1.2 after effects