Most of us start out as stage actors. We generally understand the rehearsal and performance process and the various requirements for an actor in a theatre setting. It may be difficult for a theatre actor to know how to adapt their acting for film. There are many technical constraints and considerations that make the film world very different.
If you don't have much or any film acting experience, here are the key differences you should know about:
1. Performance size
The biggest, most obvious difference between screen acting and stage acting is the size of the performance. Michael Caine famously said that theatre acting is "an operation with a scalpel" and "movie acting is an operation with a laser." This difference is most stark when it comes to close-up shots. With close-ups, the actor must use much finer tools; so much can be communicated with eye movement, the turning of the face, an eyebrow lift. Relaxation and trust are key. My biggest suggestion to help maintain relaxation is to KEEP BREATHING. Holding your breath will lock you up and make you more stiff and nervous, which the camera will see.
This difference in size is often described as theatre acting requiring exaggerated expressions and louder voices, and film acting requiring smaller expressions and subtler voices. While this is ultimately true, I don't think it's particular helpful for actors to conceptualize it in this way. If an actor merely thinks of theatre acting as moving and speaking in an exaggerated way, they're liable to perform "bigly" but in a way that is disconnected and untruthful. Same with film acting: if an actor merely thinks they must be small for a film performance, they'll shrink their voice, they'll shrink their movement, and ultimately shrink their presence. This will result in a weak and tepid performance.
No matter the medium, an actor's performance, at it's core, must be rooted in living truth. It requires strong objectives, strong relationships, etc. So what is the better way to think about this? The adjustment is best conceptualized as living fully to the capacity of the required space. In theatre, you must live fully in a bigger space. It sounds corny, but your life force must extend to the back row. Think of it as a flame of energy that is radiating out from you. How far does that flame need to extend? In film, that flame typically does not need to go very far. It can be kept like a candle close to the chest. You can actually play scenes at the same scale as real life. The camera can see your thoughts.
The frame of the shot constrains what type of movement is available to the actor. There are a few types of shots that are very commonly used in film: an establishing wide shot (also called a long shot, full shot, or master shot) which captures the setting where the scene takes place and will probably contain the actor's whole body, a medium shot which typically captures the actors from the torso up, and then the close-up which focuses on the head and face of the actors. It's important to know what the shot is, so you can adjust accordingly. If you're ever not sure, just ask. Ask where the edge of the frame is and how much freedom you have to move. As an actor, it's good to know what the camera will be doing, what it will be capturing, if it will be moving or not, etc.
Also, in film, there is no audience really. The only real "audience" you have is the other person or people you are speaking to in the scene. They are the only ones that need to be able to hear and understand you. So the proximity of the other actors is another consideration that determines your performance.
Check out the below clip from Michael Caine's workshop Acting in Film which demonstrates how to adjust performance size to the frame of the shot:
2. Maintaining film continuity.
What is film continuity? I already explained that a scene often uses a few different types of shots: establishing, medium, and close-up. The editor cuts between these different shots to create the scene. The shots need to be consistent with each other so they can be matched. If they can't be properly matched, the scene won't make sense.
There is often a crew member that is assigned to keep track of continuity. They'll take pictures of the set and actors to make sure all props, setting, costumes, etc. remain the same in each take. You as the actor must be aware enough to maintain continuity in your performance. Precision and consistency are key. Editors often use an actor's physical action to cut to a different shot. This is called "cutting on action" or "matching on action." If you wave with your right hand in the master shot, but you wave with your left hand in the medium shot, or if you do it on different lines, the shots won't match.
Small mistakes in continuity actually don't matter all that much (audiences don't really pay attention to those details as long as they're engrossed in the story) and a good editor will know when to sacrifice continuity for the sake of a great performance. But if you are VERY inconsistent in your performance, you really hamstring the editor, and you'll make a lot of your footage unusable.
To maintain continuity, you have to plan and remember your physical actions. When the blocking gets set, be sure you remember it in detail. Make sure all of your actions are simple, discrete (meaning with a clear beginning and end), and repeatable.
Check out the below clip for a demonstration:
3. Little to no rehearsal time.
With theatre, you typically have about 4-6 weeks of rehearsal to explore your character and the play, and you do it as an ensemble with your other castmates. With film, rehearsal is often a luxury many productions don't have. Because of this, preparation is a much more solitary task for a film actor. If you're one of the lead actors, you will probably have the chance to have conversations with the director before shooting to make sure your visions are aligned for the character and the performance. But anything beyond that is unlikely.
It's important you have your role all worked out; your characterization needs to be fully formed on Day 1 of shooting. You should be ready with a strong take on the character, with strong ideas and choices. But you also need to remain flexible, so you can adapt to any technical circumstances or the input of the director as well as the performances of the other actors. The set will determine a lot of what you can and cannot do physically. And you might not know the exact look and feel of the set until you get there. You will need to be able to adapt accordingly.
Come up with a few choices or interpretations of how you might play certain moments or scenes. But don't lock things in so rigidly until you actually come to shoot the scene and can see all the elements you'll be working with.
Any rehearsal that happens on set is mainly for technical purposes. It's generally used to block the scene, rehearse any camera movements, and to figure out how the set needs to be lighted. But of course use that time to work things out, warm things up, and get in the right mindset. A good director should be fairly generous and accommodating and will do their best to help you give your best performance. So if you need any adjustments or clarification on anything, don't be afraid to ask.
Also, there is often a lot of downtime between set-ups where you can rehearse and run lines with the other actors if you need to. But ultimately, you need to be amply prepared prior to shooting.
4. Working amidst technical constraints and distractions.
In theatre, the technical elements of the production are added to the show during tech week, the week just prior to opening night. On a film set, every single day is tech week. Actors are only a tiny part of the filmmaking process. Their performances are the surface skin of what is really an elaborate machine. An army of unseen crew members, often standing just outside the frame of each shot, are the real ones doing the heavy lifting. You might be shooting a close, intimate scene, and in actuality there will be a person crouched next to you holding a light, or the microphone guy is hovering above you. You have to be able to ignore all of that and maintain your focus. You can't let these things derail or distract you from your performance. Meditation can help as practice for this because it trains you to be able to control, shift, and concentrate your attention.
Sometimes you have to hit it a mark precisely or you have to move or angle yourself in a way that feels awkward but is necessary for technical reasons. Your job as an actor is to act truthfully and naturally despite all of that.
Filmmaking is slow and painstaking. Small things you have no control over, such as noise or a camera flub, can ruin a take. More complicated scenes and shots sometime require a coordinated maneuver involving the actors, the camera, and the crew. It can be a complicated dance that needs to be done just right. The camera itself has its own performance. And the camera operators might ask for additional takes to perfect that camera performance. The hope is that the actors' best performance and the camera's best performance coincide in the same take.
You, as the actor, must be aware of these technical needs, you have to conform to them, but you can't let it show in your performance. Your performance has to remain natural, fresh, newly minted, and in the moment, despite all the technical constraints. It's definitely challenging and requires physical and mental adroitness.
Check out this scene from the 1995 film Living in Oblivion. The circumstances are exaggerated for comedic effect, but it accurately captures the absurd frustrations and technical problems that can occur when making a movie:
5. Shooting the story out of order.
The shooting schedule of a film will be based on the logistics of what saves the most time and money. If two different scenes are shot in the same location, they will typically be scheduled for the same shoot date. Because of this, scenes are usually shot out of order. (They are also often shot in short chunks rather than long, continuous scenes.) You might shoot the ending scene before you've shot the beginning scene. For an actor this can be challenging because you won't necessarily have the experience of shooting earlier scenes to draw on for your performance in the current scene. You won't have that momentum to build on like you do in a theatre performance. You have to use your imagination to fill in those gaps.
With film acting, you have to be more vigilant about keeping track of where you are in the story. You have to have a really good grasp of the overall storyline and the emotional throughline, so you can start at any point and know what's already happened in the story leading up to that point.
6. Multiple takes.
This can be a boon to actors; you get multiple chances to get your performance just right. Also, if the director so wishes, you can perform part of a scene in a few different ways, capturing those varying interpretations in different takes, which creates options to choose from when they get into editing.
Unlike with theatre acting, you are not the one in control of your actual performance. What makes it on the screen is not really up to you. The editor creates your performance; you just provide the raw materials.
7. The importance of listening and reacting.
I always recommend paying ample attention to the lines of the other characters in a scene so you can remain engaged and listening and react properly to their lines. This is even more important in film acting. In theatre, the audience naturally focuses on the character that happens to be speaking. In film, reaction shots of listening characters are just as important as shots with dialogue.
Really analyze your scene partner's lines. How does your character feel about what that other person says? What thoughts come up? What does it trigger? How is your character propelled to react? Which reactions are expressed and meant to be seen by the other person? Which reactions are hidden and suppressed, bubbling beneath the surface, which only the camera can see?
You as the listening character must have a silent journey, a kind of inner monologue. Your reactions must be specific, not generic. And you must have variety in your reactions. They can't all be the same.
Check out the clip below to hear Michael Caine explain the importance of listening and reacting in film acting:
Watch the below scene from the Tarantino movie Inglourious Basterds to see a masterful demonstration of keen listening and reacting done by the actress Melanie Laurent. In this scene, her character Shosanna is speaking to the Nazi (Hans Landa, played by the amazing Christoph Waltz) who killed her family. He does not recognize her as she has adopted a fake identity as a non-Jewish Frenchwoman. Her reactions in this scene show her hidden fear and disdain: