Operating the system

Gaining maximum control over the system requires practice. The student should take notes and compare the results with the actions taken. Mistakes may be made initially but these mistakes will lead to a greater understanding of the system. Testing the accuracy of exposure and negative processing is crucial to obtaining precise control over the zone system. The photographer is advised to limit the combined choice of camera, light meter, film, developer, enlarger and printing paper until this control has been achieved, otherwise variations in outcome are inevitable.

Jana Liebenstein

Choice of camera, light meter and film

Use a camera and a light meter that provide accurate exposures. If the camera or meter receives a shock through impact, the equipment should be checked. Some retail outlets will offer to test the accuracy of the equipment. Select only one type of 100 ISO film until control has been achieved. The student should ideally have some experience of processing this film prior to using it for the zone system. Establish an ‘exposure index’ for the film (see activity below). The usable speed for the film may vary from the manufacturer’s recommended speed due to a variety of reasons.

Activity 3

Using black and white negative film, take several exposures of a subject with a four stop range. Someone wearing a white shirt with dark trousers or jacket would be ideal. Calibrate the exposure using a reflected light meter reading taken from a gray card. The subject should be illuminated with diffused light (cloud cover or shade). Bracket the exposures (1/3 stop intervals) keeping a precise record of each frame. Process the negatives according to the manufacturer’s specifications. View the negatives on a light box and choose the best exposure with the assistance of an experienced practitioner. The darkest tones of the subject should render full texture and detail (no area of the image should appear clear). Choose the best exposure and check your records to find the degree of compensation required. For example, if the best exposure for accurately rendering shadow detail is 2/3 stop more than the manufacturer’s recommendation of 100 ISO then proceed to rate the film at 2/3 stop less, i.e. 64 ISO.

The zone system can be approached in a series of sequential steps. The entire system can be divided into two main practical skills. These are: ~ Exposing for the shadows. ~ Processing for the highlights.

Exposing for the shadows View the subject and choose the dark shadows that you want to be able to see full detail and texture in when you view the final image. Take a specific reflected light meter reading from one of these dark shadow tones. Use a hand-held meter at close range or fill the frame of a 35mm SLR with the selected tone. Use a spot meter to isolate a tone from a distance. Place the shadow tone in Zone III by stopping down two stops from your meter indicated exposure or MIE (e.g. if the light meter reading of the shadow tone is f4 @ 1/125 second then the final exposure could be f8 @ 1/125 second). This action is called ‘exposing for the shadows’.

Processing for the highlights View the subject and choose the bright highlights that you want to be able to see full detail and texture in when you view the final image. Take a specific reflected light meter reading from one of these bright highlights. Measure how many stops brighter the highlights are than the shadows metered for in the previous step. If the shadow tone meter reading was f4 @ 1/125 the highlight tone may measure f16 @ 1/125 (four stops difference). For bright highlights to record as bright highlights with full detail and texture they must fall in Zone VII (four stops brighter than the shadows). If this is the case the negatives can be processed normally. If the highlights measure more or less than four stops, decrease or increase processing time accordingly (see ‘Compression’ and ‘Expansion’).

Metering for the shadows and processing for the highlights

It is recommended that ‘one shot’ development (tank development using freshly prepared developer which is discarded after the film is processed) is used in conjunction with a standard developer. Developers such as D-76 and ID-11 are ideal for this test. The student should use the same thermometer of known accuracy (check it periodically with several others) and adhere to the recommended development times, temperatures and agitation. A pre-wash is recommended to maintain consistency. Viewing the negatives - the highlights of a high-contrast subject should be dark but not dense when the negatives are viewed on a light box. Newspaper print slid underneath the negatives should easily be read through the darkest tones of the image. Manufacturer’s numbers and identifying marks on pre-loaded film should appear dark but not swollen or ‘woolly’. The student should view the negatives in the presence of an experienced practitioner to obtain feedback.

Compression

If the selected highlights measure five or six stops brighter than the shadows placed in Zone III they will fall in Zone VIII or IX respectively. No detail will be visible by processing and printing the negative normally. The highlight tones selected can be moved one or two zones down the scale to Zone VII by decreasing the processing time. This situation is often experienced with a high to extreme subject brightness range (SBR). Moving the highlights one zone down the scale is referred to as N‒1, moving the highlights two zones down the scale is referred to as N‒2. N‒1 negatives are processed for approximately 85% of the normal processing time, N‒2 negatives for approximately 75% of the normal processing time when using 100 ISO film. The action of moving highlight tones down the zone scale is called ‘compaction’ or ‘compression’. Shadow tones remain largely unaffected by reduced processing time so the final effect is to lower the contrast of the final negative.

Expansion

If the selected highlights measure only two or three stops brighter than the shadows they will fall in Zone V or VI respectively. Highlights will appear dull or gray if the negatives are processed and printed normally. The highlight tones selected can be moved one or two zones up the scale to Zone VII by increasing the processing time. This situation is often experienced with a low SBR or flat light. Moving the highlights one zone up the scale is referred to as N+1, moving the highlights two zones up the scale is referred to as N+2. N+1 negatives are processed for approximately 130% of the normal processing time, N+2 negatives for approximately 150% of the normal processing time when using 100 ISO film. The action of moving highlight tones up the zone scale is called ‘expansion’. Shadow tones remain largely unaffected by increasing the processing time so the final effect is to increase the contrast of the final negative.