Pre-grading / final grading order

Why not to apply the final grading to the source plates before compositing and work with material which has the final look and style?
It's possible to apply the same grading to all the layers including practical elements, 3D renders, particles and so on and merge all this together, isn't it?

Well, imagine you are severely tinting the shadows to green, highlights to yellow and midtones to blue with the color grading and then merging a black defocused object over a bright background.
The bright background will be tinted to yellow.
The black defocused object will be thoroughly tinted to green (as shadows), but it's got soft semi-transparent edges, and those edges, mixed with the bright background, are going to shift from shadows to midtones and highlights.
However, according to your grading, midtones should be tinted to blue, and highlights to yellow, not to green.
That's why it's better to apply grading afterwards, to avoid luminance ranges shift.

So, to get the correct result with proper edge colors and properly colored semi-transparent areas you need to work with completely neutral linear images with the black and white points properly set.

© 23.07.2010 Gregory Chalenko