The Zone System and Digital Contrast Control

In Chapter 2, I used the myth of the ancient diabolical innkeeper Procrustes as an analogy for how the Zone System allows you to modify the contrast of your negatives so that they print well on the grade of photographic paper that you prefer for your work.

The myth tells the story of how Procrustes would either stretch his unwitting shorter clients on a rack until they were long enough for his bed, or chop off their legs if they were too tall.

This is similar to the way that the Zone System allows you to systematically either expand or compress the contrast of your negatives so that they match the "Procrustean Bed" of your chosen photographic paper grade.

Here's a quick review of how this process works.

The first step is to carefully meter the subject area that you want to be Zone III, dark with full texture and detail.

We have learned that light meters always recommend exposures for what they see that will print Zone V or middle gray. Therefore, if we were to use the meter's recommended exposure for this area, the negative would be overexposed by two stops.

FIGURE 104 Zone V placement of an area previsualized as Zone III.

Stopping down two stops will place the meter reading for the area previsualized as Zone III on Zone III where it belongs. If, as in this example, the Important Highlight Falls on the appropriate Zone149149 then the negative would receive Normal Development.

FIGURE 105 Zone III placement of an area previsualized as Zone III.

If the Important Highlight reading Falls too low on the Zone Scale we would need to increase the development time to stretch the contrast of the negative until it matches the paper's tonal scale.

This is called N + Development; in this case, N + 2.

FIGURE 106 The effect of Normal Plus Two Development.

If the subject's Important Highlights Fall too high on the scale, we reduce the negative development time enough to compress the highlights until they fit properly on the scale. This is known as N - Development; in this case, N - 2.

FIGURE 107 The effect of normal minus two development.

The reason this process works is because film is an inherently analog, continuous tone medium that, within limits, allows for the compression or expansion of negative contrast without the problems we discussed that are associated with digital processes.

Many photographers have had the experience of seeing a negative that has detail in highlight areas that's visible when viewed against a strong enough light source, but simply won't print on contemporary photographic papers.

This demonstrates that the detail was present in the latent state of that image and could have been rendered printable if the development time had been correct.

Digital imaging processes behave in a very different way.

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