Grading is the process of adjusting the color of a clip to get the best out of the material or to match shots perhaps taken at different times or in different lighting conditions. With film, grading was traditionally performed when going from internegative to print film by controlling the exposure of the film. In television it was traditionally done off the telecine for commercials or tape-to-tape for longform programs. Either way, both processes were, by their nature, linear.
The advent of non-linear grading systems (such as Quantel’s Pablo Rio) has changed the rules for color grading and correction. While there is still a requirement for an initial technical scan for film-originated material, from this point on grading can – and often does – happen at multiple stages in the post production process. For example, color correcting individual layers within multilayer composite shots (which may be shot under different lighting conditions) to ensure that the result is harmonious within itself. In addition, non-linear editing means that scene-to-scene comparisons and corrections can be made as the edit unfolds.
This eases the final grading process when the finished work is reviewed interactively with the director/client.
Secondary color correction is aimed at controlling a particular color or a narrow range of colors – such as those on a car or product. Here typically the hue, gain and saturation can be changed. There are also several methods available for defining the object, area or ‘window’ that requires color correction such as using wipe-pattern shapes, drawing an electronic mask by hand or a combination of automatic and by-hand methods. Some of the most sophisticated tools are provided by media workstations such as Quantel’s Pablo Rio.