It's safe to say that when watching someone who is watching someone have sex, or touching themselves on screen, we get altered in some way. It is not just the sexual excitement of watching someone and being hidden but also, knowing that someone else is watching with us. Voyeurism has many assumptions applied to it in movie formats. I believe one that sticks out is the fact that a secret is shared simultaneously. Consider that a person who is making love or touching themselves in secrecy, is aware that no one else is in the room or nearby to listen/watch. The voyeur knows that it is the sexual person's secret to be having sex, but it is now a secret that that person is sharing. To heighten the idea, consider that the person making love knows that they are not being watched, so the voyeur has a secret. Now the viewer does too, since they secretly watch what a voyeur has secretly recorded. It becomes rather more interesting when the person in the sexual act knows of someone watching but disregards it, in order not to scare away the voyeur, in which case now the person with the sexual act has the ultimate secret, especially if it is not shared even with the viewer in a video.