Copyright LX
Cinematic Expression - Light Direction
Frontal -  Key position front and at eye level. Flat, characterless lighting. Eliminates wrinkles. Gives
definite eye light. Television news style.

Butterfly - Raised Key produces nose shadow in the form of butterfly. Single light Butterfly created
famous Marlene Dietrich look with accentuated chick bones.

Loop - Key moved slightly to the right as to extend nose shadow downwards to the corner of lip.
Neutral lighting style between feminine and masculine qualities.

Rembrandt - King of all lighting styles. Characteristic feature: triangle of highlight on the Fill side.
Style frequently used in Noir  and mystery moods. Very masculine and dynamic style.
Applied with women to imply "vampy" or a Look of ambiguous qualities: "Rebeca", Hitchcock.

Side -  Clean and very effective style lending itself to creation of Noir. Key light does not contaminate
background  which makes the style effective and quick in Noir Mood application.
Direction of Key Light determines the portraiture style. Existence of Portrait Style in Master Shot is irrelevant as long as general
direction of light and relative contrast ratio between Ambiance and Key are preserved in CU coverage.
Ambiance and Key Light are main building blocks of any lighting situation. Position of Key Light determines Lighting Style in CU.
There are five basic styles of CU where each suits and/or enhances general lighting style.:
Frontal - Butterfly - Loop - Rembrandt - Side

Some of the Styles are are considered to be "Feminine" and some - "Masculine".
One needs to follow One's sense of sensibility in choosing CU Lighting Style as generally it should relate to established
atmosphere.  
Frontal Style of CU within Low Key Chiaroscuro Mood would be a mistake.

I was asked by student once : "Why the Style" ... ?
Well ... Light is like Life... One can go through it with or without style. It is the matter of personal choice.
Rembrandt Style