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Grain is a basic characteristic of film that is derived from the individual silver halide crystals randomly distributed across an image. The random distribution of these crystals creates the visual impression of graininess, which adds a distinctive look to film. In addition, different film stocks have different grain signatures.
You can use grain management tools to create convincing composites between video, or CG-generated elements, and film material. The DeGrain and ReGrain tools are useful in a number of scenarios. For example:
- If you are pulling keys from key-in film clips, film grain can make generating a clean matte more difficult. Using the DeGrain tool, you can remove the grain from the key-in clip, generate the matte from that clip, and apply the matte to the original grainy key-in clip. The result is a clean, precise matte applied to a properly grainy film clip.
- If you are mixing film clips originating from different film stocks, you can match the grain in the clips to make the grain in your results look consistent.
- If you are working with footage originally shot on film and transferred to video, you can remove the grain and match the film material with video material.
- If you are working with video material or CG-generated elements, you may want to add grain to the clips to result in a film look.
- You can use DeGrain tools to remove grain from film clips before performing any image processes. After you are finished, you can use ReGrain tools to restore the film grain to the final result.
Grain management workflow, much like working with LUTs, depends heavily on the specific qualities of the media you are working with. Use the procedures described in the following sections to put together the processing steps that you need to get the results that you want.