Long takes can do a lot for your narrative film, but they are as difficult as they are beneficial.
Getting Your Scenes
In narrative film production each scene is constructed through a series of takes. Each take runs through the scene either partially or completely, focusing on a different angle or character in each take. From here you head to the editing room and construct the scene out of the various takes, each one put together so that the audience will focus on a specific aspect at the scene at a specific time. In this way the entire scene is then laid out with the correct visuals happening at the right time. At times you may want to have each take occur for an extended period of time, maybe even longer than you anticipated the entire scene taking. These long takes have their own special challenges but can end up giving you things you never expected.
Long takes are not always used for directly scripted film projects. If a scene is carefully written then it is usually hard to have an extended video sequence. The reason for this is that film scenes are not usually that long over all. Usually a scene is allowed to run for a longer period of time when there is more of an outline than a specifically decided rhythm. To make a long take work you have to allow the scene to progress outside of the bounds you may have planned for.
The most difficult part of using long takes is that a long period of time will require the actors to move around for that period of time. In this way it is hard to match up various takes because their movements may not match up. It is easy for actors to always hit their various marks within the space allowed when the scenes are short, but if the take goes much farther in length it may be required for them to move even more to keep the portrayal accurate. When planning long takes you may have to accept the fact that the scene itself may be only able to utilize a couple, or even a single, take for the entire scene.
When planning a long take you will likely have to use specific camera work that is different than the rest of the shoot. You usually only have two choices for this, using a free handheld camera or placing a stationary camera far away from the action so that you are able to see everything that happens. The handheld, or steadicam, approach is usually best for this because then you can get close to the actors and follow them openly as they move about the space. One of the more common types of long takes that happen in larger films is to follow the actors as they move through a long open space, capturing all the events that occur around them. More recently we have seen this with films that utilize warfare as a central theme, as with the long tracking shots in Atonement and Children of Men. This is difficult because you must not only plan with the main actors for this, but make sure that the entire location, with all of the special effects and extras, move correctly for a very long period of time and in perfect rhythm.
Inside the Characters
The major advantage to using long takes is to allow the actors to stay in character longer, a fact which allows them to take more risks. This allows it to have the spontaneity and commitment that is often seen in theater, and this is the unique feature that lets filmmakers like Woody Allen and Lars von Trier really provoke their actors on set. The problem is that this puts a lot of pressure on the performers to have a perfect scene and to keep it visually interesting.
Before you decide to do the scene in one long extended take try rehearsing the scene repeatedly. Make sure that all actors in the scene are hitting their marks correctly and that they will be able to work with the camera without distraction or hesitation. This is not an easy technique, but it can really highlight a complex moment in your project.