Lighting

Lighting is an important signifier in that it conveys the mood or atmosphere of the scene we are observing. In a studio, the lighting is usually from three sources and is set up as following:

The Key Light: Usually the brightest and the most influential.
The Back Light: Helps counteract the effect of key light, thus making the figure (or subject) more 'rounded'
The Filler Light(s): Helps to soften the harsh shadows that the use of back and key light creates.

High Key and Low Key Lighting:

The director manipulates this basic format to achieve the atmosphere s/he wishes to convey. If s/he only used the key and back lights, they will produce a sharp contrast of dark and light areas on the screen as the shadows are formed. This is known as low-key lighting and is often seen as expressive.  High-key lighting means that more filler lights are used. This will appear more normal and realistic to out eyes but can also be manipulated to give more of a glamorous appearance to a star's face or add a 'twinkle' to their eyes (This 'twinkle' is called a catchlight)