Why are props and lighting important in a movie?

I require supporting stement not just thoughts.....Please give reasons why props are important...and why are lighting effects important.....i also need to know how can lighting change mood of plot in a movie....thnx!!!!!!!Why are props and lighting important in a movie?
Props are important because they are provide details about a character's personality (a closet full of shoes, stuffed animal), environment (a messy apartment), even their political or social viewpoint (a poster on the wall that says ';Love Stinks'; or ';I hate Bush';).



Lighting is important because in combination with camera placement and motion, it focuses the viewer's attention on what the director feels is important in a scene or a sequence of scenes (all scenes involving a particular character). What's important may be a tangible object (like the things mentioned earlier) or intangible (to set a mood).



How you will accomplish this depends on the story you're trying to tell, but I suggest reading any or all of these:

1. American Cinematographer magazine

2. Film Art by David Bordwell

3. the documentary Visions of Light (1992)