Editing Zone System (section)

=== Roll film ===

Unlike sheet film, in which each negative can be individually developed, an entire roll must be given the same development, so that N+ and N− development are normally unavailable.<ref>
If a roll-film camera accepts interchangeable backs, it is possible to use N+ and N− development by designating different backs for different development, and changing backs when the image so requires. Without interchangeable backs, different camera bodies can be designated for different development, but this usually is practical only with small-format cameras.
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The key element in the scene is placed on the desired zone, and the rest of the scene falls where it will. Some contrast control is still available with the use of different paper grades. Adams (1981, 93&ndash;95) described use of the Zone System with roll film. In most cases, he recommended N&nbsp;−&nbsp;1 development when a single roll was to be exposed under conditions of varying contrast, so that exposure could be sufficient to give adequate shadow detail but avoid excessive density and grain build-up in the highlights.