CGCookie - Fundamentals of Compositing

https://cgcookie.com/courses/fundamentals-of-compositing

• When people say "fix it in post", this is what they mean. Compositing is sort of like Apple TV -- in that it's very useful but can be difficult to explain and understand. So let's break it down into a problem --> solution explanation. Rendering is always the bottleneck of a production pipeline due to the extended time required to render a CG animation. So when we commit to render a Blender animation, wait hours or days for it to finish, only to decide after the fact that we want the [metallic material] to reflect 50% less, our only choice is to make that change in the blender material, then render and wait again. This is where compositing comes in. Someone had the brilliant idea to separate rendered elements - like objects, material color, reflections, blender lights, etc - so they could be tweaked individually after rendering. Now to continue with the previous example, we could reduce reflections by 50% with the compositor in 5 seconds instead of waiting hours to render the whole scene again. That's the meat and potatoes of compositing. We can take this blender basics workflow to our advantage.