How can I clean up grainy digital footage shot in low-light conditions?
Internet Filmmakers' FAQ
Short answer: you cant't.
Long answer: with a lot of work in a program like Motion or After Effects and some complex masks and filters like gaussian blur and unsharp mask, you might be able to SLIGHTLY improve your image quality. Generally, however, it's not worth the effort and you should either reshoot the footage or settle for what you got.
Answer by Andrew Gingerich, | Last updated 13-Dec-2005