...In the theatre, the spectator is stationary as he watches and listens to the spectacle moving before him. If an actor has to give emphasis to a particular gesture or expression he must draw the attention of the audience to himself by taking up a conspicuous position, or by striking a pose or making a movement or pause that will lead the other actors to look at him; and whatever he does must be performed so obviously that it cannot fail to be observed by the most distant members of his audience. His makeup, even his stage-whispers, must be exaggerated for the same purpose.

In a film, none of this is necessary.
The fundamental difference between the methods of the theatre and the film involves considerable differences between the technique of stage acting and that of film acting. In the first place, the exaggeration and overstatement which the stage actor has to employ become quite unnecessary in the film. On the contrary, because the camera can approach so close and give such an enlarged view of the least detail, it is restraint and understatement which are required. ("I had always believed," George Arliss tells us, "that for the movies acting must be exaggerated, but I saw in this one flash, that "restraint" was the chief thing that the actor had to learn in transferring his art from the stage to the screen.")
All that is essential and effective on the stage, the wide sweep of gesture, the make-up, the declamatory style of speech, becomes false and ridiculous on the screen simply because it is out of place. "When we speak of the 'unnecessary staginess,' of a film actor's performance, we so term it not because staginess necessarily involves anything of itself wrong or unpleasant. We simply register an unpleasant sensation of incongruity, and therefore falseness, as though at the sight of a man striving to negotiate a nonexistent obstacle."

A second difference is that whereas on the stage an actor's chief instrument of expression is his voice, and his movements are almost entirely an accompaniment to, and an extension of, what is said, in the film he acts with the whole of himself. A glance, a movement of the hand, a slight shrug of the shoulders may be far more significant than anything said. This means that the film actor must exercise a far higher degree of self-control. Falseness and insincerity are much more apparent in a screen performance than on the stage, where, as Robert Donat has testified, it is easier for the actor to disguise an imperfectly assimilated characterization. "In the theatre," he says, "it is the audience which receives; in the studio it is the camera, with this surprising difference that whereas one can get away with flippancy, sloppiness and insincerity in the theatre, infinite care must be exercised in front of the camera. In the theatre the broad methods necessary to reach topmost galleryite and lowermost pittite sometimes cover a multitude of sins."

To make the same point in a slightly different way, whereas stage acting is to a considerable extent conventionalized and stylized, film acting is in the highest degree naturalistic, nothing is so effective on the screen as complete sincerity, provided always that it is tempered with restraint.

1. stationary — not moving or changing position; cf. remain stationary — remain in the same place
2. overstatement — an exaggerated statement; an exaggeration; cf. understatement=a statement which is excessively restrained
3. we simply register art unpleasant sensation — we merely feel unpleasantly affected
4. to negotiate an obstacle — to show a certain skill in overcoming an obstacle; to get past or over smth.
5. to get away with smth. — to do something with impunity, i. e. without ill effect for oneself
6. galleryite — a spectator in the lower gallery; pittite—a spectator in the pit; cf. standing-roomite