I use some general rules for adding filters. The first is that if there's noise intentionally added to the movie you have to decide whether you prefer the encoding artifacts that will probably be created by lowering the bitrate, the changes to the look of the film, or the inconvenience of splitting the movie across multiple discs.
Only your own eyes can tell you whether the results are acceptable or not. Beyond that I use the following:
General cleanup of film grain:
Very noisy source, poor transfer/encode on original, or high compression:
Good black and white source:
Noisy black and white source:
Poor quality black and white source:
Notice that Undot is always first and Greyscale is always last. Anything Undot would remove may be gone by the time it runs if the video has already been altered, and if you use Greyscale after Deen you may avoid having Deen mistake noise for part of the image.
If you decide to experiment with other filters you need to consider these kinds of things when you determine their order.
Written by: Rich Fiscus