Cinematography and Editing.

Film noir was marked on its visual expressionistic lighting and the deep focus and the depth of field. They would jar editing or use juxtapositioning of elements to baffle the audience and make the storylines seem more misleading. Some of the elements they made sure they would use in editing are shadows, skewed camera angles, cigarette smoke and gloomy appearances. This straight away gives the depressive feel straight away, in which noirs would try to acheieve. The settings tended to be claustrophobic and with low key lighting. This gave a more personal feel. It's like you are on the charecters level in the small room as a voiceover plays about the bad they have done.They used confusing fades and transitions to keep the audience feeling quite unsettled. They would put use piano music to underlie the becoming story line to give a seedy or erratic feel [depending on what scene is playing]