Zone system

The zone system is a term from analog black and white photography and describes a technical process for optimizing the central influencing factors in the production of black and white single negatives.

In contrast to the photochemical standard development processes of analog color photography , the development of black and white material is extremely variable and thus enables a precise, differentiated translation of brightness into analog density differences of negative films by adapting not only the exposure but also the development time to the scene to be photographed becomes. As a result, the zone system in the classic sense is limited to the processing of single negatives, such as those used in large format cameras. In practice, the type of development to be used will be limited to a few options (N-2, N-1, N, N + 1, N + 2), intermediate stages (N-1.3) are very atypical. The zone system can therefore also be used with medium format cameras with removable magazines without any problems.

The primary aim is to systematically exploit the chemical-technical potential of analog black-and-white image storage, above all from the point of view of maximum tonal value and its consistent implementation up to the finished, positive top-view image - but also the optimal mastery of the photographic craft that does not fail "allows, leaves nothing to chance and thus reduces the high material costs in large-format photography to the bare minimum.

Basic principles

In his book trilogy, which is very well known in specialist circles, the American photographer Ansel Adams (1902–1984) published the 'zone system', which is often ascribed to him, which in an individual process of adapting the prevailing motif contrast of a recording situation , the exposure range of the information storage used black and white film, the density range of the negative according to his photochemical development as well as the final positive production in the laboratory process. Ultimately, it is about a calculated control of these processes, which are decisive for the image process, recording / image storage / film development / positive process with the help of a theoretical construction of 11 (zone 0 to zone 10) densitometrically precisely calibrated master gray values, each of which is a light value in its blackening differ from each other.

For the analog production of a top view image (positive) using the negative-positive process, two separate processes are basically necessary: the creation of a negative as the actual image memory in a suitable camera and the transfer of the contrast range of the photo- chemically developed negative onto the photo paper in the positive process .

The range of negative density of the film and the range of copying of the photo paper differ considerably - since the classic zone system only works with the paper gradation "normal", the range of density of the negative must be adjusted to the range of copying of the photo paper by means of modified development parameters.

Originally, the system propagated by Ansel Adams only included the creation of a technically optimal negative - later attempts were made to include the other process steps up to the finished print.

Previsualization and contrast control

The idea of pre-visualization plays a central role in the concept . The aim of this pre-visualization is to a certain extent an inner idea of the image effect together with the associated photographic-technical consequences before the actual recording process. Would the photographer like If, for example, a gloomy mood with heavy tonal values could be evoked , normal exposure with the associated average subject brightness would miss the intended interpretation.

To achieve the intended image effect, certain parts of the motif would have to be reproduced much darker than normal. To achieve this goal, it is necessary to keep an eye on the contrast range of the image during the entire processing chain.

The zone system takes into account that the contrast range of a photo paper is less than that of a film or the actual motif. This leads to the fact that z. For example, in the case of high-contrast landscape photographs, the scale of the tone or gray values from black to white cannot technically be transferred from the negative to the paper.

The negative contrast can be adjusted by controlling the development parameters: A longer exposure of the film and a subsequent shortened development results in a lower contrast (“smaller” tonal range), the image effect tends to be soft. A shortened exposure in combination with a longer development allows the black and white values to stand out more clearly with flat subject contrasts, thus increasing the contrast.

Zone system with digital technology

The considerations of the zone system also apply in a similar way to other recording methods, i.e. also to the CCD or CMOS sensor of a digital camera , the computer monitor and printing, e.g. B. with inkjet or laser printer.

The printout (the paper form of the picture) again has the most limited range of contrast. A monitor can display an additional contrast range that is still limited compared to the original. With the appropriate software, digital image processing offers much more extensive possibilities, so gray values can be adjusted individually or in relation to each other, which is only feasible in the darkroom with great effort or not at all. A creative redesign becomes possible, but the boundaries to image manipulation are fluid.

Another advantage of digital photography is that shortly after the picture has been taken, a histogram or the monitor display can be used to roughly assess whether there is overexposure or underexposure. As with an analog camera, the aperture and time can be changed, especially with stationary subjects, until the intended contrast ratios are achieved. This means that - as is the case with negative or slide film - one does not need to wait for the film to develop in order to be able to assess whether the exposure was correct or according to the requirements.

Several differently exposed images can be combined with one software. If, for example, the range of brightness of the subject exceeds the sensitivity range of the image sensor, images with different exposures can be combined on the computer to ensure drawing in both light and dark image sections (see HDRI generation from exposure series ). The result is a so-called HDR image with a high dynamic range . In order to be able to display these recordings on conventional media, their dynamic range must be compressed and adjusted using a tone mapping process.

Some digital image sensors not only offer the required fine grayscale (bit range of the brightness signal), but can even compress extreme contrast ratios without loss of information by means of a sequence of logarithmically graded exposure times of the individual pixels.

Allocation of zones and exposure control

Adams divided the reproducible range of contrast of a photo into 11 (labeled 0 to 10) areas or zones. The distance between the zones corresponds to a full f-stop (1EV).

Zero stands for deep black without drawing, ten denotes pure white without drawing. Five corresponds to the so-called neutral gray with 18% reflection. The area that can be copied onto photographic paper in the laboratory comprises the nine zones from I to IX; the marked, detailed area the zones II to VII.

Is a spot exposure meter (in the camera or light meter), a part of the subject appropriate to the exposure value represents the zone V (18% neutral gray) - All exposure meters are calibrated thereto.

However, it is possible to assign a different measured value or a different zone to this part of the subject in order to change the effect on the photo:

If the zone is to be shown dark but with a drawing in the picture, it could be assigned to zone III. If the exposure meter shows e.g. If, for example, 1/30 s and f 8.0 were used, then 1/30 would have to be used for f 16. All other motif parts of the picture also fall into a different tonal value range or zone, depending on the selected exposure. In this way, it is possible to control the brightness or the contrast with which the relevant parts of the image are reproduced.

If, for example, an image-important part of the subject falls into Zone IX with the selected exposure, i.e. white with almost no drawing, only a dull image effect would result, which may not correspond to the photographer's ideas. There is no such thing as a “correct” or “correct” exposure - rather, the photographer chooses exposure values that lead to an image that has the intended effect on the viewer.

The exposure values are therefore dependent on the subject, the desired photographic and artistic effect as well as the development and can vary upwards or downwards. The boundaries between a good shot, suitable photographic technology and revealing hidden details, artistic freedom and manipulation are fluid. B. be transformed into a sunset.

Exposure in practice

Adams introduced numerous methods of calibration, influencing contrast and other things and used them to create his large format photographs. Not all of them can be used with the 35mm films most commonly used today. The essentials of the zone system can, however, be implemented if a camera with manual adjustment is available.

A structured surface that corresponds roughly to a medium gray, such as a doormat or a wall, is recorded “normally” and full-frame with the selected camera-film combination (or the corresponding digital camera setting). It results, with regular exposure metering, z. B. the exposure 1/30 f 8. This now corresponds to Zone V, now, for other zones, further pictures are taken with different exposure values:

Zone 0 1/125 f 22
Zone I 1/60 f 22
Zone II 1/30 f 22
Zone III 1/30 f16
Zone IV 1/30 f11
Zone V 1/30 f8
Zone VI 1/30 f5.6
Zone VII 1/30 f4
Zone VIII 1/15 f4
Zone IX 1/8 f4
Zone X 1/4 f4

Of course, any other time or aperture combination can also be selected according to the light value of the zone V recording, provided that it maintains the distance of one aperture stop or time step (= 1 EV) from one another for different zones. It is always helpful to note down the number of the respective picture together with exposure (aperture and time) and zone. With the log, a wealth of experience can be built up that can be accessed later.

The recordings are now developed or reproduced or projected in the desired but previously considered form, in the simplest case simply given to the laboratory or printed out. For prints from the laboratory, it is necessary to use the zone system to find a laboratory that offers the option of doing without automatic exposure corrections, as otherwise all prints will be corrected back to neutral gray. This should be inquired about or determined by test, but is usually possible at specialist dealers. The eleven developed images (according to the above zones) now show the contrast range and the drawing of the selected reproduction chain; the values can also be traced using the log. There may be details; H. Tone value and contrast, already no longer fully visible for Zone III or Zone VII shows the last usable light drawing. It is therefore necessary or possible to produce a series of exposures for each reproduction chain (from camera and lens to film (or sensor and a certain setting) to positive / projection / screen). The results of these series of exposures can in future be used to design images (visualization).

Experience shows that viewers perceive recordings as “well” or “correctly” exposed in which the contrast range has been used as much as possible. The recording technique for this would be to pay attention to (two) parts of the motif, which should be shown in white or black in the final image without drawing details. The parts of the motif that are important to the image should be in the area marked out in between, and the exposure frame should be adapted to the zone system if possible.

Films and color

In the case of negative films , the determined brightest usable zone (on the film) can be selected as the base zone , which is then used to correct exposure. It is appropriate to that part of the motif that is just about to be shown with a drawing dark (= light area on the negative film) on the print, in the example corresponding to Zone III. Then the exposure is selected two f-stops or time steps higher (i.e. f / 4 instead of f / 8 or 1/60 s instead of 1/250 s). Now it is determined in which zone the brightest part of the subject falls. If it is within the determined area drawn, the exposure is optimal.

In the case of slide films , conversely, the lowest (brightest) usable zone is selected as the base zone. This procedure is also sensible because in films the dark areas (with negative films correspondingly the lightest parts of the image) “run in” faster and no longer show any details than comparatively the lightest (darkest) areas.

The light (or dark) areas can also be corrected better in post-processing, if available. A slight overexposure with negative films or slight underexposure with slide films can therefore be tolerated under certain circumstances. In the case of slides for projection as well as in the absence of processing options, the light and dark borders must of course be selected correctly.

While the original zone system was mainly used for black and white photography, color films are predominantly used today, which in the following also allow other design measures. The contrast correction with a filter on the camera itself has become a bit unusual, but the color temperature can be influenced. For modern films, the changed contrast range in the zone system must be taken into account. In the case of color films, the difference to the black and white material is usually small, but greater in the case of slide films. This and the subjective effect of the color should be taken into account when recording in the zone system. The sensor system of digital technology is in turn comparable to the slide film in terms of tonal value, plus the noise and other peculiarities.

Limits of the zone system

The photographic work with the zone system was conceived for working with a large-format camera and the associated possibility of developing individual films - it unfolds its optimal potential especially where the photographer has the necessary time to calmly measure the subject and subject contrast with the spot exposure meter and to coordinate with film development - primarily landscape, portrait or still life shots.

All subject areas that work with small film formats and require dynamic and fast photographic access, such as B. sports photography , street photography or reporting are rather unsuitable for systematic work with the zone system.

On the other hand, the high didactic value of the zone system, with the help of which fundamental relationships in black and white photography are clarified, is still undisputed today.

Despite changing gradation papers and extremely high-performance films that are now available, it is certainly useful as a foundation for optimal technical mastery of the photographic craft and for the conscious use of these photographic-technical means to sharpen photographic expression.

literature

Ansel Adams: The camera. Christian Verlag, Munich 2000, ISBN 3-88472-070-8 .
Ansel Adams: The negative. Christian Verlag, Munich 1998, ISBN 3-88472-071-6 .
Ansel Adams: The positive. Christian Verlag, Munich 1998, ISBN 3-88472-072-4 .
Peter Fischer-Piel: The zone system in black and white and color photography. ikoo Buchverlag, Berlin 1988, ISBN 3-88677-929-7 .
Henk Roelfsema: The zone system: control of contrast in black and white photography. Verlag Photographie, Schaffhausen 1992, ISBN 3-7231-0017-1 .
Minor White: The New Zone System Manual. Morgan & Morgan, New York 1990, ISBN 0-87100-100-4 . (English)