Editing Zone System (section)

=== Exposure zones ===

In the Zone System, measurements are made of individual scene elements, and exposure is adjusted based on the photographer's knowledge of what is being metered: a photographer knows the difference between freshly fallen snow and a black horse, while a meter does not. Much has been written on the Zone System, but the concept is very simple&mdash;render light subjects as light, and dark subjects as dark, according to the photographer's visualization. The Zone System assigns numbers from 0 through 10<ref>
Adams (1981) designated 11 zones; other photographers, including Picker (1974) and White, Zakia, and Lorenz (1976) used 10 zones. Either approach is workable if the photographer is consistent in her methods.
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to different brightness values, with 0 representing black, 5 middle gray, and 10 pure white; these values are known as ''zones''. To make zones easily distinguishable from other quantities, Adams and Archer used Roman rather than Arabic numerals. Strictly speaking, zones refer to exposure,<ref>
Adams (1981) distinguished among ''exposure zones'', ''negative density values'', and ''print values''. The negative density value is controlled by exposure and the negative development; the print value is controlled by the negative density value, and the paper exposure and development. Commonly, "zone" is also used, if somewhat loosely, to refer to negative density values and print values.
</ref> with a Zone&nbsp;V exposure (the meter indication) resulting in a mid-tone rendering in the final image. Each zone differs from the preceding or following zone by a factor of two, so that a Zone&nbsp;I exposure is twice that of Zone&nbsp;0, and so forth. A one-zone change is equal to one stop,<ref>
Photographers commonly refer to exposure changes in terms of "stops", but properly, a [[Aperture stop|stop]] is a device that regulates the amount of light, while a step is a division of a scale. The standard exposure scale consists of power-of-two steps; a one-step exposure increase doubles the exposure, while a one-step decrease halves the exposure. Davis (1999, 13) recommended the term "stop" to avoid confusion with the steps of a photographic step tablet, which may not correspond to standard power-of-two exposure steps. ISO standards generally use "step".
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corresponding to standard aperture and shutter controls on a camera. Evaluating a scene is particularly easy with a meter that indicates in [[exposure value]] (EV), because a change of one EV is equal to a change of one zone.

Many small- and medium-format cameras include provision for [[exposure compensation]]; this feature works well with the Zone System, especially if the camera includes spot metering, but obtaining proper results requires careful metering of individual scene elements and making appropriate adjustments.