After Tom has openly accused his brother of forgery, as shown by the cut-in leader, the scene changes to the hallway outside the library door.  We see Wilkins, the butler, who is implicated in the plot against Ralph, kneeling and peering into the room through the key-hole.  This is a very short scene, but it is necessary to show two things:  not only that the brothers are being spied upon, for we are not interested in merely watching the butler kneeling there, but it is important for us to see what he is watching so intently—­the action in the library.  So, after we have shown the spy kneeling outside the door, the scene is shifted back to the continuation of the interview between Tom and Ralph.  This time, however, we see it on the screen in a way that merely suggests the butler kneeling outside the closed door.  On the screen appears a large key-hole, and within its limits the scene between the brothers is acted.

The effect thus produced is termed a “mask.”  Ordinarily the lens of a moving picture camera is masked by a metal plate, rectangular in shape, one inch wide by three-quarters of an inch high.  The use of this mask prevents the light from spreading up or down the film as it is being exposed.  As explained in Chapter III, each of the sixteen tiny pictures that make up a foot of film is termed a “frame,” and, the camera being masked as described, the light is permitted to act upon only one frame at a time.  But within this limit of one inch by three-quarters of an inch another mask may be used, cut in any form that the producer may desire.  It may be a key-hole mask, as in the foregoing example; it may be simply circular, to suggest that the scene is viewed through a telescope; or a mask with hair-line bars, which will suggest that you are looking through a window.  We examined a script a short while ago in which a travelling salesman for an optical goods house amused himself in the interval before train time by watching through a pair of binoculars the street below and the buildings opposite his hotel window.  The scene enacted in an office of a building not far away led him to believe that a murder was being committed, and the action which followed was extremely funny.  The scene in the office, watched by the “drummer” through the binoculars, appeared on the screen as though viewed through a large and very round figure eight, lying on its side, thus:  [symbol:  figure-eight].

The four just mentioned are the commonest forms of the mask; but we have seen masks cut in the shape of oak leaves, bottles, and other forms, though these latter were used merely to obtain novel effects.

The mask may be used as an inserted scene—­as we have here chiefly considered it—­or it may serve as a sort of excuse for the entire action of the photoplay, as in the case of the commercial traveller and his binoculars, and add effectiveness by its novelty of presentation.

12.  The Bust and the Close-up