Quality of light

Light Contrast
Looking back on high and low key lighting, contrast is range of tones between black and white that the key lighting was trying to amplify. Low contrast shots have a wide range of view and have a softer look to them, although the colour and tones aren't as strong. High contrast shots, on the other hand, have a much smaller range and a harder look to them.

Hard and Soft Light
As I mentioned above, I used the term "softer" and "harder" in reference to lighting. Diving deeper into this, the quality of light that we see on screen is labelled as "hardness" and "softness". A hard quality shot has a sharper look to it with darker shadows while a soft quality shot uses lighter and more subtle shadows.

Colour
The colour of the shot (also known as the hue) is achieved from lighting, art direction and laboratory procedure and the colour of the shot can have an effect on what the scene is trying to convey to the audience. The overall hue can be tinted a certain colour in order to invoke a certain emotion or time of day to a location in an effort to make the audience feel something. For example, blue can be used for sadder scenes while red is used for more intimate moments. The time of day is represented by colour too such as yellow for sunrise and blue for night.

The colour saturation is how richer colours are conveyed on screen. Saturated colours appear more vibrant while desaturated colours are more barren and bleak. Saturation is traditionally used for emotion or time frame. Flashbacks are generally desaturated to make is appear older.

Colour can also have strong emphasis as the film can draw the audiences eye towards a certain object. This idea can also be used in black and white films to make something of importance stand out. A great example of this is in Steven Spielburg's 1993 film 'Schindler's List' which, while filmed entirely in black and white, features a girl wearing a red coat. This is the only colour in the film and is used to shock the audience when they see the red stand out among a pile of corpses after becoming acquainted with the coat.

Sources: Film School Online - Attributes of the Visual Image