Editing Zone System (section)

== Principles ==

=== Visualization ===

An expressive image involves the arrangement and rendering of various scene elements according to the photographer's desire. Achieving the desired image involves ''image management'' (placement of the camera, choice of lens, and possibly the use of [[View camera#Movements|camera movements]]) and control of ''image values''. The Zone System is concerned with the control of image values, ensuring that light and dark values are rendered as desired. Anticipation of the final result before making the exposure is known as ''visualization''.

=== Exposure metering ===

Any scene of photographic interest contains elements of different [[luminance]]; consequently, the "exposure" actually is many different exposures. The exposure time is the same for all elements, but the image [[illuminance]] varies with the luminance of each subject element.

Exposure is often determined using a reflected-light<ref>Adams (1981, 30) considered the [[Light meter|incident-light meter]], which measures light falling ''on'' the subject, to be of limited usefulness because it takes no account of the specific subject luminances that actually produce the image.
</ref> [[Light meter|exposure meter]]. The earliest meters measured overall average luminance; [[Light meter#Exposure meter calibration|meter calibration]] was established to give satisfactory exposures for typical outdoor scenes. However, if the part of a scene that is metered includes large areas of unusually high or low reflectance, or unusually large areas of highlight or shadow, the "effective" average reflectance<ref>
A typical scene includes areas of highlight and shadow and has scene elements at various angles to the light source, so it usually is possible to use the term "average" reflectance only loosely. Here, "effective" average reflectance is used to include these additional effects.
</ref>
may differ substantially from that of a "typical" scene, and the rendering may not be as desired.

An averaging meter cannot distinguish between a subject of uniform luminance and one that consists of light and dark elements. When exposure is determined from average luminance measurements, the exposure of any given scene element depends on the relationship of its reflectance to the effective average reflectance. For example, a dark object of 4% reflectance would be given a different exposure in a scene of 20% effective average reflectance than it would be given in a scene of 12% reflectance. In a sunlit outdoor scene, the exposure for the dark object would also depend on whether the object was in sunlight or shade. Depending on the scene and the photographer's objective, any of the previous exposures might be acceptable. However, in some situations, the photographer might wish to specifically control the rendering of the dark object; with overall average metering, this is difficult if not impossible. When it is important to control the rendering of specific scene elements, alternative metering techniques may be required.

It is possible to make a meter reading of an individual scene element, but the exposure indicated by the meter will render that element as a medium gray; in the case of a dark object, that result is usually not what is desired. Even when metering individual scene elements, some adjustment of the indicated exposure is often needed if the metered scene element is to be rendered as visualized.

=== 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.
</ref>
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".
</ref>
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.

=== Zones, the physical world and the print ===

The relationship between the physical scene and the print is established by characteristics of the negative and the print.
Exposure and development of the negative are usually determined so that a properly exposed negative will yield an acceptable print on a specific photographic paper.

Although zones directly relate to exposure, visualization relates to the final result. A black-and-white photographic print represents the visual world as a series of tones ranging from black to white. Imagine all of the tonal values that can appear in a print, represented as a continuous gradation from black to white:
{|align=center style=width:33em;border-spacing:0
|+Full Tonal Gradation
|-
|style=padding:0|<div style="background:white;width:30.2em;border:1px solid black;box-sizing:border-box;overflow:clip;height:3em">{{for nowiki|>|<div style{{=}}background:rgba(<nowiki>{{loop|3|{{#expr:255-({{{1}}})}},}}1);width:{{#expr:(ln(((1.055-({{{1}}})/255)^.8+(1.055-(({{{1}}})-1)/255)^.8)^3/((1.055-1/255)^.8+1.055^.8)^3)/ln(2)+10)*3}}</nowiki>em|count=255}};height:3em>{{loop|255|</div>}}
|}
From this starting point, zones are formed by first dividing the tonal gradation into ten equal sections, all one stop apart, plus one more for blown-out paper white.
{|align=center style=width:33em;border-spacing:0
|+Eleven-Step Gradation
|-
|style=padding:0|<div style="background:white;width:30.2em;border:1px solid black;box-sizing:border-box;overflow:clip;height:3em"><div style=height:.2em>{{for nowiki|>|<div style{{=}}background:rgba(<nowiki>{{loop|3|{{#expr:255-({{{1}}})}},}}1);width:{{#expr:(ln(((1.055-({{{1}}})/255)^.8+(1.055-(({{{1}}})-1)/255)^.8)^3/((1.055-1/255)^.8+1.055^.8)^3)/ln(2)+10)*3}}</nowiki>em|count=255}};height:3em>{{loop|256|</div>}}<div style="margin-left:-1px;{{for nowiki|"><div style{{=}}"|width:<nowiki>{{#expr:33-({{{1}}})*3}}em;border-right:1px solid#{{#ifexpr:({{{1}}})>5|555|000}}</nowiki>|count=10}};height:2.5em></div>
|}
:'''Note:''' ''The darker shades may not be distinguishable on some monitors.''
Then for each section, one average tone represents all the tonal values in that section.
{|align=center style=width:33em;border-spacing:0
|+Eleven Symbolic Tones
|-style=height:3em
|style="border:1px solid black;background:rgba({{loop|3|{{#expr:((((1-1/255/1.055)^.8)+1)^3)*3294.6*2^-12.5}},}}1)"|
|style="border:1px solid black;background:rgba({{loop|3|{{#expr:((((1-1/255/1.055)^.8)+1)^3)*3294.6*2^-11.5}},}}1)"|
{{for nowiki||<nowiki>|style{{=}}"border:1px solid black;background:rgba({{loop|3|{{#expr:(1.055*(((((1-1/255/1.055)^.8)+1)^3)*2^(({{{1}}})-11.5))^(1/2.4)-.055)*255}},}}1)"|</nowiki>
|count=8}}|style="border:1px solid black;background:white"|
|}
Finally, the zones are defined by numbering each section with Roman numerals from 0 for the black section to X for the white one.
{|align=center style=width:33em;border-spacing:0;text-align:center
|+The Zone Scale
|-style=height:3em
|style="width:9%;border:1px solid black;background:rgba({{loop|3|{{#expr:((((1-1/255/1.055)^.8)+1)^3)*3294.6*2^-12.5}},}}1);color:#555"|0
|style="width:9%;border:1px solid black;background:rgba({{loop|3|{{#expr:((((1-1/255/1.055)^.8)+1)^3)*3294.6*2^-11.5}},}}1);color:#555"|I
{{for nowiki||<nowiki>|style{{=}}"width:9%;border:1px solid black;background:rgba({{loop|3|{{#expr:(1.055*(((((1-1/255/1.055)^.8)+1)^3)*2^(({{{1}}})-11.5))^(1/2.4)-.055)*255}},}}1);color:#{{#ifexpr:({{{1}}})<4|555|000}};{{#ifeq:{{{1}}}|4|font-size:150%}}"|{{#switch:{{{1}}}|1=II|2=III|3=IV|4=V|5=VI|6=VII|7=VIII|8=IX}}</nowiki>
|count=8}}|style="width:9%;border:1px solid black;background:white;color:black"|X
|}

=== Zones as tone and texture ===

Adams (1981, 52) distinguished among three different exposure scales for the negative:

* The full range from black to white, represented by Zone&nbsp;0 through Zone&nbsp;X.
* The ''dynamic range'' comprising Zone&nbsp;I through Zone&nbsp;IX, which Adams considered to represent the darkest and lightest "useful" negative densities.
* The ''textural range'' comprising Zone&nbsp;II through Zone&nbsp;VIII. This range of zones conveys a sense of texture and the recognition of substance.

He noted that negatives can record detail through Zone&nbsp;XII and even higher, but that bringing this information within the exposure scale of the print is extremely difficult with normal processing.

Adams (1981, 60) described the zone scale and its relationship to typical scene elements:<ref>
Adams's description of zones and their application to typical scene elements was somewhat more extensive than the table in this article. The application of Zone&nbsp;IX to glaring snow is from Adams (1948).
</ref>
{| align="center"
! Zone !! Description
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #000000; color: #fff; font-weight: bold; width: 3em; margin: 0; text-align: center;" | 0
| style="padding-left: 2em;" | Pure black - no detail
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #1a1a1a; color: #fff; font-weight: bold; width: 3em; margin: 0; text-align: center;" | I
| style="padding-left: 2em;" | Near black, with slight tonality but no texture
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #333333; color: #fff; font-weight: bold; width: 3em; margin: 0; text-align: center;" | II
| style="padding-left: 2em;" | Textured black; the darkest part of the image in which slight detail is recorded
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #4d4d4d; color: #fff; font-weight: bold; width: 3em; margin: 0; text-align: center;" | III
| style="padding-left: 2em;" | Average dark materials and low values showing adequate texture
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #666666; color: #fff; font-weight: bold; width: 3em; margin: 0; text-align: center;" | IV
| style="padding-left: 2em;" | Average dark foliage, dark stone, or landscape shadows
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #808080; color: #fff; font-weight: bold; font-size: 150%; width: 3em; margin: 0; text-align: center;" | V
| style="padding-left: 2em;" | Middle gray: clear north sky; dark skin, average weathered wood
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #999999; color: #fff; font-weight: bold; width: 3em; margin: 0; text-align: center;" | VI
| style="padding-left: 2em;" | Average Caucasian skin; light stone; shadows on snow in sunlit landscapes
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #b3b3b3; font-weight: bold; width: 3em; margin: 0; text-align: center;" | VII
| style="padding-left: 2em;" |  Very light skin; shadows in snow with acute side lighting
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #cccccc; font-weight: bold; width: 3em; margin: 0; text-align: center;" | VIII
| style="padding-left: 2em;" | Lightest tone with texture: textured snow
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #e6e6e6; font-weight: bold; width: 3em; margin: 0; text-align: center;" | IX
| style="padding-left: 2em;" | Slight tone without texture; glaring snow
|- style="height: 3em;"
| style="border: 1px solid black; background-color: #fff; font-weight: bold; width: 3em; margin: 0; text-align: center;" | X
| style="padding-left: 2em;" | Pure white: light sources and specular reflections - paper white, no detail
|}

For cinematography, in general, parts of the scene falling in Zone&nbsp;III will have textured black, and objects on Zone VII will have textured white. In other words, if the text on a piece of white paper is to be readable, light and expose the white so that it falls on Zone&nbsp;VII. This is a rule of thumb. Some film stocks have steeper curves than others, and the cinematographer needs to know how each one handles all shades of black-to-white.