Although I have never seen the movie, I do know all about the shades of grey =) #shadesofgrey
It is an important part of setting your tonal values for the image you would like to capture. Any “good” “professional” photographer will know this. Not only is it having the knowledge about tonal values and zones but also how your camera sees a scene and meters for it and what will you do with your camera to adjust it to set your zones where you want them. Setting it on “P” or any auto setting won’t cut it.
Wiki: The Zone System provides photographers with a systematic method of precisely defining the relationship between the way they visualize the photographic subject and the final results. Although it originated with black-and-white sheet film, the Zone System is also applicable to roll film, both black-and-white and color, negative and reversal, and to digital photography.
An expressive image involves the arrangement and rendering of various scene elements according to the photographer’s desire. Achieving the desired image involves image management (placement of the camera, choice of lens, and possibly the use of camera movements) and control of image values. The Zone System is concerned with control of image values, ensuring that light and dark values are rendered as desired. Anticipation of the final result before making the exposure is known as visualization. http://en.wikipedia.org/wiki/Zone_System
Here are my shades of grey =)