This is all no-brainer, but there is another expanded element (not so much in this, yet very much in this and kind of what Life touches upon) which is the conditioning prior to the scare.
For example like Rik says a girl descends the steps from the second floor of a creepy dark house on a stormy dark night, she walks over to a window.
Right there you could startle us (The audience) with a face in the window, but you could also start playing with our minds by framing the shots and using actions that make the girl more vulnerable.
If the window is favored in the framing of the shot then tension begins in us, like “Oh man there is going to be a flash of lightening and a scary face in that damn window - I just know it!”, but that doesn’t happen, instead there’s a little non scary noise, the girl turns and sweeps her flashlight across the room, it illuminates an old clock…
We feel like “No big deal, I knew by the sound it was just a clock.” , but now the girl’s back is turned to the window, so she is even more vulnerable, and we are like, “Don’t turn your back on the window, it’s out there fool!!!!”, then the door opens, her friend enters and says “There you are. Didn’t you hear me calling you?” and the girl says “No I didn’t shi—“ -CRASHHH!!- The Killer comes through the window and scares the crap out of us!
This isn’t the best example, but the point is to engage and pre-condition the audience with a series of visual tension builds and releases with framing, actions, easing in of the camera, shots that are closer to the window for example and more -so that ideally when the time comes, every step the character takes has us on and off edge till we are the victim of a sucker punch scare we knew was coming, but fell victim to by letting our guard down when the visual tension was released on screen.
The reason I mention all of this is because in this clip, look at the points of vulnerable entry and elements of distraction in the shot (A doorway, a window, a window, a table in the lower left, flashes of something on the right, things on the floor we are trying to make sense of) all of it has our eyes jumping around looking for where the Boogie Man is going to come from (and thus invoking tension), then when the chair moves our focus goes to the center, and the tension drops with the logic of “Big deal it’s just a chai--“ SCARE!
-Thanks-
