The key light notes

• The key light is the principal light source. Its position is related to the subject direction and not the camera.
• Consider the key light's position both vertically and laterally, and its colour temperature (warm or cool). Adjust the steepness of the key light by changing its height and distance. Get it steep enough to create shadows under the cheekbones and low enough to just get into the eyes forming catchlights.
• When the shadow of the nose breaks the cheek shadow and encloses a triangle of light on the unlit side of the face it is often called the Hollywood triangle. People often refer to it as Rembrandt lighting but when I studied Rembrandt as a student I only found a few self-portraits that used this lighting style.
• ‘Down the nose' lighting is where the light is positioned in line with the subject's nose.
• A Fresnel lens or adaptor can change the light from hard to soft and deliver a beautiful transition from lit to unlit. It is far more efficient at creating a pool of light than a grid attached to a reflector.
• Diffusing a light using frost gel creates a loss of control over the light's direction.
• A honeycomb grid gives a degree of control over the direction of soft light and can aid in keeping it off the background.
  
  

A note about upstage lighting

Theatrical stages are built on an incline that tilts slightly downward toward the audience. So "downstage" is the lower third of the stage closest to the audience and "upstage" is the upper third furthest away. By using the camera position as a reference point, similar to the audience perspective in the theatre. A light rigged closer to the camera than the subject is downstage, and further away is upstage. By using upstage lighting the shadows will fall towards the camera rather than away from the camera.

Shooting into the unlit side of the face looks fabulous.