The Zone System is a photographic technique for determining optimal film exposure and development, formulated by Ansel Adams and Fred Archer.
[1] Adams described the Zone System as "[...] 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.
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[4] may differ substantially from that of a "typical" scene, and the rendering may not be as desired.
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.
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.
A black-and-white photographic print represents the visual world as a series of tones ranging from black to white.
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.
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.
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.
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.
One of the first was Fujifilm's FinePix S3 Pro digital SLR (released in 2004), which has their proprietary "Super CCD SR sensor" specifically developed to overcome the issue of limited dynamic range, using interstitial low-sensitivity photosites (pixels) to capture highlight details.
[citation needed] The CCD 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.
It often suffices to make two exposures, one for the shadows, and one for the highlights; the images are then overlapped and blended appropriately, so that the resulting composite represents a wider range of colors and tones.
Similarly, the density range of a traditional photographic print depends on the processes used as well as the paper characteristics.
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, or ISO speed, to ensure a tonally rich starting image.
[11] The Zone System gained an early reputation for being complex, difficult to understand, and impractical to apply to real-life shooting situations and equipment.
Criticism has been raised on grounds that the Zone System obscures simple densitometry considerations by needlessly introducing its own terminology for otherwise trivial concepts.
Noted photographer Andreas Feininger wrote in 1976, I deliberately omitted discussing the so-called Zone System of film exposure determination in this book because in my opinion it makes mountains out of molehills, complicates matters out of all proportions, does not produce any results that cannot be accomplished more easily with methods discussed in this text, and is a ritual if not a form of cult rather than a practical technical procedure.
Fred Picker (The Zone VI Workshop 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.