How The Over Operation Works

In this video I break down the maths behind an over operation. I also look back at the history of how these composites were done before we had digital compositing, and show that the concepts behind the operation haven't actually changed much since the beginning. This video assumes that you understand what a premultiplied image is, and continues on from my previous video that explains premultiplication. If you don't understand premultiplication you should watch that video before you watch this one: https://youtu.be/dwtP5Q3Tg6g There is a written version of this video on my website: http://conradolson.com/how-the-over-operation-works In this video I referenced the following sources: FStoppers.com - Behind the Scenes: Special Effects Used In Silent Films: https://fstoppers.com/education/behind-scenes-special-effects-used-silent-films-161538 FXGuide.com - The Role of the Optical Printer: https://www.fxguide.com/fxfeatured/fxphd-the-role-of-the-optical-printer/ BBC Horizon - How To Film The Impossible: https://www.youtube.com/playlist?list=PLNNgLd-WEDOfv1AAr_piE-fObEqNmF3CP