Editing Zone System (section)

=== Development ===

For every combination of film, developer, and paper there is a "normal" development time that will allow a properly exposed negative to give a reasonable print. In many cases, this means that values in the print will display as recorded (e.g. Zone&nbsp;V as Zone&nbsp;V, Zone&nbsp;VI as Zone&nbsp;VI, and so on). In general, optimal negative development will be different for every type and grade of paper.

It is often desirable for a print to exhibit a full range of tonal values; this may not be possible for a low-contrast scene if the negative is given normal development. However, the development can be increased to increase the negative contrast so that the full range of tones is available. This technique is known as ''expansion'', and the development usually referred to as "plus" or "N+". Criteria for plus development vary among different photographers; Adams used it to ''raise'' a Zone&nbsp;VII placement to Zone&nbsp;VIII in the print, and referred to it as "N&nbsp;+&nbsp;1" development.

Conversely, if the negative for a high-contrast scene is given normal development, desired detail may be lost in either shadow or highlight areas, and the result may appear harsh. However, development can be reduced so that a scene element placed on Zone&nbsp;IX is rendered as Zone&nbsp;VIII in the print; this technique is known as ''contraction'', and the development usually referred to as "minus" or "N−". When the resulting change is one zone, it is usually called "N&nbsp;−&nbsp;1" development.

It sometimes is possible to make greater adjustments, using "N&nbsp;+&nbsp;2" or "N&nbsp;−&nbsp;2" development, and occasionally even beyond.

Development has the greatest effect on dense areas of the negative, so that the high values can be adjusted with minimal effect on the low values. The effect of expansion or contraction gradually decreases with tones darker than Zone&nbsp;VIII (or whatever value is used for control of high values).

Specific times for N+ or N− developments are determined either from systematic tests, or from development tables provided by certain Zone System books.