Editing Zone System (section)

=== Exposure ===

A dark surface under a bright light can reflect the same amount of light as a light surface under dim light.  The human eye would perceive the two as being very different but a light meter would measure only the amount of light reflected, and its recommended exposure would render either as Zone&nbsp;V.  The Zone System provides a straightforward method for rendering these objects as the photographer desires. The key element in the scene is identified, and that element is ''placed'' on the desired zone; the other elements in the scene then ''fall'' where they may. With negative film, exposure often favors shadow detail; the procedure then is to

# Visualize the darkest area of the subject in which detail is required, and place it on Zone&nbsp;III. The exposure for Zone&nbsp;III is important, because if the exposure is insufficient, the image may not have satisfactory shadow detail. If the shadow detail is not recorded at the time of exposure, nothing can be done to add it later.
# Carefully meter the area visualized as Zone III and note the meter's recommended exposure (the meter gives a Zone V exposure).
# Adjust the recommended exposure so that the area is placed on Zone&nbsp;III rather than Zone&nbsp;V.  To do this, use an exposure two stops less than the meter's recommendation.