The Zone System
is a photographic
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
technique for determining optimal film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...
In photography, exposure is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value and scene luminance over a specified area.In photographic jargon, an exposure...
Photographic processing is the chemical means by which photographic film and paper is treated after photographic exposure to produce a negative or positive image...
, formulated by Ansel Adams
Ansel Easton Adams was an American photographer and environmentalist, best known for his black-and-white photographs of the American West, especially in Yosemite National Park....
and Fred Archer
Fred R. Archer , was an American photographer who collaborated with Ansel Adams to create the Zone System. He was a portrait photographer, specializing early in his career in portraits of Hollywood movie stars. He was associated with the artistic trend in photography known as pictorialism...
. Adams described how the Zone System was developed: "I take this opportunity to restate that the Zone System is not an invention of mine; it is a codification of the principles of sensitometry, worked out by Fred Archer and myself at the Art Center School in Los Angeles, around 1939-40."
The technique is based on the late 19th century sensitometry
Sensitometry is the scientific study of light-sensitive materials, especially photographic film. The study has its origins in the work by Ferdinand Hurter and Vero Charles Driffield with early black-and-white emulsions...
studies of Hurter and Driffield
Ferdinand Hurter and Vero Charles Driffield were nineteenth-century photographic scientists who brought quantitative scientific practice to photography through the methods of sensitometry and densitometry....
. The Zone System provides photographers with a systematic method of precisely defining the relationship between the way they visualize the photographic subject and the final results. Although it originated with black-and-white
Black-and-white, often abbreviated B/W or B&W, is a term referring to a number of monochrome forms in visual arts.Black-and-white as a description is also something of a misnomer, for in addition to black and white, most of these media included varying shades of gray...
Sheet film is large format and medium format photographic film supplied on individual sheets of acetate or polyester film base rather than rolls. Sheet film was initially supplied as an alternative to glass plates...
, the Zone System is also applicable to roll film, both black-and-white and color, negative and reversal, and to digital photography
Digital photography is a form of photography that uses an array of light sensitive sensors to capture the image focused by the lens, as opposed to an exposure on light sensitive film...
An expressive image involves the arrangement and rendering of various scene elements according to photographer’s desire. Achieving the desired image involves image management
(placement of the camera, choice of lens, and possibly the use of camera movements) and control of image values
. The Zone System is concerned with 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
Almost any scene of photographic interest contains elements of different luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square...
; consequently, the “exposure” actually is many different exposures. The exposure time is the same for all elements, but the image illuminance
In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with human brightness perception. Similarly, luminous emittance is the luminous flux per...
varies with the luminance of each subject element.
Exposure is often determined using a reflected-light
A light meter is a device used to measure the amount of light. In photography, a light meter is often used to determine the proper exposure for a photograph...
. The earliest meters measured overall average luminance; 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
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.
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—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
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, with a Zone 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 I exposure is twice that of Zone 0, and so forth. A one-zone change is equal to one stop,
corresponding to standard aperture and shutter controls on a camera. Evaluating a scene is particularly easy with a meter that indicates in exposure value
In photography, exposure value denotes all combinations of a camera's shutter speed and relative aperture that give the same exposure. In an attempt to simplify choosing among combinations of equivalent camera settings, the concept was developed by the German shutter manufacturer in the 1950s...
(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
Exposure compensation is a technique for adjusting the exposure indicated by a photographic exposure meter, in consideration of factors that may cause the indicated exposure to result in a less-than-optimal image. Factors considered may include unusual lighting distribution, variations within a...
; 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:
From this starting point, zones are formed by:
- Dividing the tonal gradation into eleven equal sections.
- Note: You may need to adjust the brightness and contrast of your monitor to see the gradations at the dark and light end of the scales.
- Blending each section into one tone that represents all the tonal values in that section.
- Numbering each section with Roman numerals from 0 for the black section to X for the white one.
The Zone Scale
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 0 through Zone X.
- The dynamic range comprising Zone I through Zone IX, which Adams considered to represent the darkest and lightest “useful” negative densities.
- The textural range comprising Zone II through Zone VIII. This range of zones conveys a sense of texture and the recognition of substance.
He noted that negatives can record detail through Zone 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:
| Zone || Description
|| Pure black
|| Near black, with slight tonality but no texture
|| Textured black; the darkest part of the image in which slight detail is recorded
|| Average dark materials and low values showing adequate texture
|| Average dark foliage, dark stone, or landscape shadows
|| Middle gray: clear north sky; dark skin, average weathered wood
|| Average Caucasian skin; light stone; shadows on snow in sunlit landscapes
|| Very light skin; shadows in snow with acute side lighting
|| Lightest tone with texture: textured snow
|| Slight tone without texture; glaring snow
|| Pure white: light sources and specular reflections
For cinematography, in general, parts of the scene falling in Zone 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 VII. This is a general 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.
Effective film speed
The ISO standard for black-and-white negative film, ISO 6:1993, specifies development criteria that may differ from those used in practical photography (previous standards, such as ANSI PH2.5-1979, also specified chemistry and development technique). Consequently, the Zone System practitioner often must determine the speed for a particular combination of film, developer, and enlarger type; the speed determination is commonly based on Zone I. Although the method for determining speed for the Zone System is conceptually similar to the ISO method for determining speed, the Zone System speed is an effective speed
rather than an ISO speed.
A dark surface under a bright light can reflect the same amount of light as a light surface under dim light. The human eye would perceive the two as being very different but a light meter would measure only the amount of light reflected, and its recommended exposure would render either as Zone V. The Zone System provides a straightforward method for rendering these objects as the photographer desires. The key element in the scene is identified, and that element is placed
on the desired zone; the other elements in the scene then fall
where they may. With negative film, exposure often favors shadow detail; the procedure then is to
- Visualize the darkest area of the subject in which detail is required, and place it on Zone III. The exposure for Zone III is important, because if the exposure is insufficient, the image may not have satisfactory shadow detail. If the shadow detail is not recorded at the time of exposure, nothing can be done to add it later.
- Carefully meter the area visualized as Zone III and note the meter’s recommended exposure (the meter gives a Zone V exposure).
- Adjust the recommended exposure so that the area is placed on Zone III rather than Zone V. To do this, use an exposure two stops less than the meter’s recommendation.
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 V as Zone V, Zone VI as Zone VI, and so on). In general, optimal negative development will be different for every type and grade of paper.
It often is 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 VII placement to Zone VIII in the print, and referred to it as “N + 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 IX is rendered as Zone 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 − 1” development.
It sometimes is possible to make greater adjustments, using “N + 2” or “N − 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 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.
Additional darkroom processes
Adams generally used selenium toning when processing prints. Selenium toner acts as a preservative and can alter the color of a print, but Adams used it subtly, primarily because it can add almost a full zone to the tonal range of the final print, producing richer dark tones that still hold shadow detail. His book The Print
described using the techniques of dodging and burning to selectively darken or lighten areas of the final print.
The Zone System requires that every variable in photography, from exposure to darkroom production of the print, be calibrated and controlled. The print is the last link in a chain of events, no less important to the Zone System than exposure and development of the film. With practice, the photographer visualizes the final print before the shutter is released.
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.
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, 93–95) described use of the Zone System with roll film. In most cases, he recommended N − 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.
Because of color shifts, color film usually does not lend itself to variations in development time. Use of the Zone System with color film is similar to that with black-and-white roll film, except that the exposure range is somewhat less, so that there are fewer zones between black and white. The exposure scale of color reversal film is less than that of color negative film, and the procedure for exposure usually is different, favoring highlights rather than shadows; the shadow values then fall where they will. Whatever the exposure range, the meter indication results in a Zone V placement. Adams (1981, 95–97) described the application to color film, both negative and reversal.
The Zone System can be used in digital photography just as in film photography; Adams (1981, xiii) himself anticipated the digital image. As with color reversal film, the normal procedure is to expose for the highlights and process for the shadows.
Until recently, digital sensors had a much narrower dynamic range than color film, which, in turn, has less range than monochrome film. But an increasing number of digital cameras have wider dynamic ranges. One of the first was Fujifilm
is a multinational photography and imaging company headquartered in Tokyo, Japan.Fujifilm's principal activities are the development, production, sale and servicing of color photographic film, digital cameras, photofinishing equipment, color paper, photofinishing chemicals, medical imaging...
’s FinePix S3 Pro
The Fujifilm FinePix S3 Pro is an interchangeable lens digital single-lens reflex camera introduced in February 2004. Its successor, the Finepix S5 Pro, was released on 25 September 2006...
digital SLR, which has their proprietary “Super CCD
Super CCD is a proprietary charge-coupled device that has been developed by Fujifilm since 1999. The Super CCD uses octagonal, rather than rectangular, pixels...
SR sensor” specifically developed to overcome the issue of limited dynamic range, using interstitial low-sensitivity photosites (pixels) to capture highlight details. The CCD
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
is thus able to expose at both low and high sensitivities within one shot by assigning a honeycomb of pixels to different intensities of light.
Greater scene contrast can be accommodated by making one or more exposures of the same scene using different exposure settings and then combining those images. It often suffices to make two exposures, one for the shadows, and one for the highlights; the images are then overlapped and blended appropriately
Tone mapping is a technique used in image processing and computer graphics to map one set of colors to another in order to approximate the appearance of high dynamic range images in a medium that has a more limited dynamic range...
, so that the resulting composite represents a wider range of colors and tones. Combining images is often easier if the image-editing software includes features, such as the automatic layer alignment in Adobe Photoshop CS3, that assist precise registration of multiple images. Even greater scene contrast can be handled by using more than two exposures and combining with a feature such as Merge to HDR
in Photoshop CS2 and later.
The tonal range of the final image depends on the characteristics of the display medium. Monitor contrast
The contrast ratio is a property of a display system, defined as the ratio of the luminance of the brightest color to that of the darkest color that the system is capable of producing...
can vary significantly, depending on the type (CRT
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
, LCD, etc.), model, and calibration
The aim of color calibration is to measure and/or adjust the color response of a device to a known state. In ICC terms this is the basis for a additional color characterization of the device and later profiling. In non ICC workflows calibration refers sometimes to establishing a known relationship...
(or lack thereof). A computer printer
In computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...
’s tonal output depends on the number of ink
Ink is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...
s used and the paper
Photographic paper is paper coated with light-sensitive chemicals, used for making photographic prints.Photographic paper is exposed to light in a controlled manner, either by placing a negative in contact with the paper directly to produce a contact print, by using an enlarger in order to create a...
on which it is printed. Similarly, the density range of a traditional photographic print depends on the process
es used as well as the paper characteristics.
Most high-end digital cameras allow viewing a histogram
An image histogram is a type of histogram that acts as a graphical representation of the tonal distribution in a digital image. It plots the number of pixels for each tonal value. By looking at the histogram for a specific image a viewer will be able to judge the entire tonal distribution at a...
of the tonal distribution of the captured image. This histogram, which shows the concentration of tones, running from dark on the left to light on the right, can be used to judge whether a full tonal range has been captured, or whether the exposure should be adjusted, such as by changing the exposure time, lens aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
, or ISO speed, to ensure a tonally rich starting image.
Misconceptions and Criticisms
The Zone System gained an early reputation for being complex, difficult to understand, and impractical to apply to real-life shooting situations and equipment. Noted photographer Andreas Feininger
Andreas Bernhard Lyonel Feininger was a German American photographer, and writer on photographic technique, noted for his dynamic black-and-white scenes of Manhattan and studies of the structure of natural objects....
wrote in 1976,
Much of the difficulty may have resulted from Adams’s early books, which he wrote without the assistance of a professional editor; he later conceded (Adams 1985, 325) that this was a mistake. Picker (1974) provided a concise and simple treatment that helped demystify the process. Adams’s later Photography Series published in the early 1980s (and written with the assistance of Robert Baker) also proved far more comprehensible to the average photographer.
The Zone System has often been thought to apply only to certain materials, such as black-and-white sheet film and black-and-white photographic prints. Adams (1981, xii) suggested that when new materials become available, the Zone System is adapted rather than discarded. He anticipated the digital age, stating
Yet another misconception is that the Zone System emphasizes technique at the expense of creativity. Some practitioners have treated the Zone System as if it were an end in itself, but Adams made it clear that the Zone System was an enabling
technique rather than the ultimate objective.
- Farzad, Bahman. The Confused Photographer’s Guide to Photographic Exposure and the Simplified Zone System. 4th ed. Birmingham, AL: Confused Photographer’s Guide Books, 2001. ISBN 0-9660817-1-4
- Johnson, Chris. The Practical Zone System, Fourth Edition: For Film and Digital Photography. 4th ed. Boston: Focal Press, 2007. ISBN 0-240-80756-1
- Lav, Brian. Zone System: Step-by-Step Guide for Photographers. Buffalo, NY: Amherst Media, 2001. ISBN 1-58428-055-7