The seven opening (discrete) is a very good opening as it is very appealing to the audience. The video doesn't really relate to the video but the clip gives the viewer a sense of what the film is about. The opening clip has also been edited with a filter which gives us the low quality effect, allowing it to have a greater spooky effect. Apart from this, the opening is very well edited. There're many cuts, a lot of quick cuts which again intensify the tension trying to be created by the producers.
Another aspect of this film is there's mainly close ups, close ups allow the viewer to feel closer to the action, so the audience feel more intimate with the film, creating even more tension.