What is enigma ? it is the questions the film asks at the beginning to keep the viewers interest. All questions relating to Who, What, When, Where, Why and How. This can be done by using close up shots on face or back of heads so the body and face isn't recognized.
For e.g. in blues brothers as one of the brothers is let out of prison there is only back of head shots and extreme close ups on his sunglasses. The characters also wear sunglasses through out the film, asking the question why. Another e.g. being the Dark Knight , in the opening scene the joker has his back turned from the camera and all the criminals have masks.
Other ways enigma can be posed is by using speeds of shots and type of camera filming, quick shots indicating urgency and danger (usually hand held shots). while slow shots are for more relaxed and mood setting scenes.
For e.g. mission impossible three , the opening scene is very quick dialogue (narrative for the first few seconds), and held camera shots and quick speed shots showing danger and setting up the mood for action and tension.
