"In pre-production every step of actually creating the film is carefully designed and planned. The production company is created and a production office established. The film is pre-visualized by the director, and may be storyboarded with the help of illustrators and concept artists. A production budget is drawn up to plan expenditures for the film. For major productions, insurance is procured to protect against accidents." - https://en.wikipedia.org/wiki/Filmmaking#Pre-production
Director: in pre-production, the director will be primarily responsible for the story telling, creative decisions and acting of the film. They have to organise everything before the film goes ahead onto the production period, and make sure everything is in place for the filming period.
Rest of the crew: for this time period, some crew members will not be hired until later on when they are needed, ie script supervisor.
However all the crew members that are already there need to be on their feet and ready to prepare for the times ahead before the film is put into action.
Production:
"The production of motion pictures and television films; the principal branch of cinematography. Film production takes place at motion-picture studios—enterprises that specialize in various types of films, such as feature motion pictures, documentaries, popular science films, educational films, and animated cartoons." -
http://encyclopedia2.thefreedictionary.com/Film+Production
Director: for the production part of the film the director has to be a big part of the film and take part in it in a huge aspect. They need to be able to be on the ball on the time and prepared for anything that goes wrong/not to plan on the set.
Rest of the crew: more crew members are hired in this stage of the film, such as the property master, assistant directors, stills photographer, picture editor and sound editors. Every single member of the crew need to be on the ball to though, because they have to be prepared to fix things if something goes wrong. They need to be able to improvise.
Post production:
"In digital film, photography, television and film, post-production refers to the tasks that must be completed or executed after the filming or shooting ends. This includes tasks such as the editing of raw footage to cut scenes, insert transition effects, working with voice and sound actors, and dubbing, to name a few of the many pre-production tasks. Post-production is the third and final step in film creation.' -
http://www.webopedia.com/TERM/P/post_production.html
Director: the director has to be around for the post production part of the film to, in order to supervise the editing of the raw footage, etc. They need to be able to tell the editors what they want, and if they have a problem they should be able to turn to him/her for help.
Rest of the crew: some of the crew for this part are not needed anymore, and so usually their jobs are done and finished. However members like the editors and sound effect people, that wouldn't have been around for the pre production, obviously have to be around for the post production. They need to be able to work well together for this final part of the film, in order to produce the best possible outcome of all the footage that the camera men captured.
