Mental image the viewer constructs while watching—independent of what's actually on screen. Each person sees something different based on personal memory and emotion.
The inner screen is the place where the film truly takes place—not on the projection surface, but in the viewer's mind. What you see on the screen is merely the offering. Each viewer constructs their own film from it, filtered through memory, experience, prior expectation, and current state. What's interesting for us as filmmakers is that we only partially control this inner process.
On set or in the edit, we work with images, cuts, sound—with everything that determines the outer screen. But as soon as the film is running, something unregulated happens. A brief glance from an actress is interpreted by person A as fear, by person B as contempt. A landscape shot evokes homesickness in one person, and mere boredom in another. This is not a weakness of the film—it is its strength. The viewer becomes a co-author. That's why suggestion often works better than explanation. A well-composed shot, quickly cut, with the right music—these leave room for the inner screen to do its work.
Practically, this means: when you're shooting a fear scene, you don't need to show everything. The cut, the glance, the sound design—they create the conditions. The viewer fills the gap with their own fear, and that is always more intense than what you could show. The same applies to grief, suspense, infatuation. The inner screen works with suggestion, rhythm, and psychological timing.
This also explains why test screenings are so imprecise. A hundred people, a hundred inner screens. One person finds the scene too long, another wishes for more time. That's normal. What's important is that the structure of the film—its editing sequence, its image compositions—provides enough support so that the viewers are not completely fragmented, but look together in the same direction, even if each sees something different.