In the context of film production, the read-through is an organized table reading of the screenplay by the actors with speaking parts. An additional professional actor not otherwise involved in the production is usually hired to read the non-dialogue parts of the script such as scene headings and action. These parts of the script are usually edited down severely for the purposes of the read-through to keep the pace of the reading up.
The read-through usually takes place towards the end of pre-production but before the rehearsal period, if any has been scheduled.
In addition to the cast members with speaking parts, the read-through is usually attended by the principal financiers or studio executives, producers, heads of department, writers, and of course directors. It is extremely rare for anyone not involved in the production to be permitted to attend. It is usually the first time everyone involved in the production will have gathered together and it is traditional to go around the table (usually a ring of tables, in fact) and allow everyone to introduce themselves by both name and job. The director may then open proceedings by making a short speech outlining his or her aspirations for the project.
The read-through is an important milestone in the production of most films. It is a clear signal that all of the key elements, including cast, finance and heads of department, are in place and that pre-production is almost complete. It is often the first time that the script has had a life beyond the written word, and it is also an opportunity for everyone involved in production to get at least a partial insight into the way the actors may approach their roles. In addition, a read-through is often a surprisingly powerful tool for identifying problem areas in the script. Wooden dialogue, unbelievable situations or boring sections of the film which have not been addressed during the script development process are often writ large in the read-through, and may now come under intense scrutiny.
It is traditional to treat the read-through as a cold reading. Because the actors have had no rehearsal time, and may not even have discussed the project much with the director, they are not expected to give a performance but simply to read the words on the page. Some actors including major Hollywood stars will indeed read their entire role in a flat monotone, whereas others (often actors from the theatre, or character actors with relatively minor parts) will 'go for it' and are often the most entertaining part of the process.
The read-through can be very nerve-wracking for the producers, director, writer and executives. Despite the fact it is supposed to be a cold reading, everyone is on the alert for possible casting or script problems -- a lack of chemistry between the principals, a key player who lacks charisma, a script which has logic problems or is obviously extremely boring. Even in their very short introduction, it may become clear that the director is unsure of himself or herself, or finds it difficult to communicate ideas. On the other hand, it can be extremely exciting to finally see a project which may have been in development for many years finally begin to take on a life of its own.
In his book Adventures in the Screen Trade, screenwriter William Goldman describes the read-through as the most important part of film production, because if the script is right and the cast is right there's not much else that can go wrong.
In an unusual example, the Space Ghost Coast to Coast episode "Table Read" consists entirely of recorded footage of a read-through for an early version of the episode "Fire Ant".