Zone System

In photography, the Zone System is a technique invented by Ansel Adams to simplify and standardise the production of black-and-white photography. The Zone System allows a photographer to translate their idea into a print.

The Zone System separates the picture's tones into eleven zones, numbered using Roman numerals.

0: Pure black

I: Near black

II: Dark gray / black

III: Very dark gray - the lowest zone with distinct shadow detail

IV: Medium dark gray

V: Medium gray (equal to Kodak's 18% Grey cards)

VI: Mid-tone gray

VII: Light gray

VIII: Gray / white - the highest zone with distinct highlight detail

IX: Near white

X: Paper base (Pure white)

The Zone System is chiefly used when exposing film, and more specifically, when deciding how to render shadow areas. Generally, the photographer wants to expose her film for the desired tone and amount of detail in the dark areas of the composition, then alter her development time to affect highlight density. What makes the Zone System so useful is the ease with which it translates desired effect to technical setting. Light meters will return the proper f-stop and shutter speed to expose the metered area at 18% middle grey - equal to Zone V. Each Zone above or below Zone V corresponds to opening or closing the aperture of the camera one f-stop. Thusly, if the photographer desires the shadow values of the dirt below a bush, for example, to be a very dark tone, but still holding detail (Zone III), she would close her aperture 2 stops from her light meter's IMR (indicated meter reading). The smaller aperture results in less light hitting the film, and consequently, darker shadow areas.

external links:

http://www.cicada.com/pub/photo/zs/