Thursday, June 24, 2010

Tone and Line in Photography and Drawing

Drawing is a binary system. In its purest form, it includes only black line and empty white space: one and zero. Forms are distinguished by tracing their edges as lines, and intermediate tones can only be simulated by a crude kind of optical illusion: that is, by cross-hatching. Line defines form.

Conversely, in a monochrome photograph, there is no absolute distinction between object and field, and there are no lines as such. A black-and-white photograph is a map of variations in tone along a single, continuous scale, which runs from pure white to pure black. This scale may be long or short, depending on contrast: that is, a high contrast image has a short tonal scale, with relatively few intermediate tones between white and black, so that the transitions from one tone to another are more visible and abrupt, whereas a low contrast image has a long tonal scale, with much smoother transitions. Another way of putting this is that, in a photograph, edge definition (known as acutance) is a function of contrast. Contrast defines form.

It therefore follows that, in a photograph, formlessness is a consequence of lack of contrast: that is, of lack of differentiation in the distribution of light. If the overall light levels are so low as to be beneath the threshold of the film or sensor, then it will process the scene as empty, and the resulting image will be pure black. Similarly, if the overall light levels are so intense as to render internal differences in reflective density between surfaces as irrelevant, then the resulting image will be pure white.

These principles also affect the distribution of light and tone within a normal image. Any given photograph will probably have some areas of ‘empty shadow’ where the light is not strong enough to cause the film to respond at all; conversely, it will also have areas of ‘blocked highlights’ in areas where the light is so intense as to overwhelm the film’s ability to discriminate between different reflective densities. The trick to exposing the image correctly is to get the balance right. In most images, this means placing the principal subject of the image at the mid-point between these two extremes. Conventionally, this mid-point is a grey tone with 18% saturation.

According to the philosophy of Ansel Adams, from whose instruction manuals I learnt how to photograph, a good print is one that exploits the entire tonal scale. For Adams, one of the great virtues of photography is its power of precise description, and the problem with high-contrast images is that they suppress detail. Adams believed that it is necessary to have small areas of pure black and pure white in a print to properly calibrate the tonal scale, but that these areas should not occupy a large part of the image’s total area, because whenever they do so, this results in loss of information. Large blank areas in a photograph are just wasted space: damning evidence that a photographer does not know how to fill them. In this approach, then, chiaroscuro effects, that is, deliberate restriction of the tonal scale in high-contrast images, are a kind of cheap melodrama, and an admission of failure on the part of a photographer who cannot find any other means to make an image eloquent. Judged on these criteria, the entire output of an artist like Bill Henson would be found wanting.

Adams did of course admit the possibility that some images might use such negative space effectively, and indeed his later prints tend more and more towards chiaroscuro, but the presumed norm for him was always maximum descriptive information, and the longest possible tonal scale. Individual scenes or prints might deviate from this norm according to the nature of the scene and the desired effect, but a photographer should have the entire tonal range available to her, even if she chooses not to use the entire range in a particular image.

When I began to photograph in Venice at night for my project Let Us Burn the Gondolas, I had Adams’ advice in mind. Initially, therefore, I tried to avoid large areas of empty black or white even in scenes that were inherently high-contrast. In part, this was to avoid fetishising the fact that I was working at night. I snobbishly despised photographers who advised increasing contrast to ensure a ‘nice night effect’. Nonetheless, the resulting images are generally ‘low-key’ (that is, dark tones predominate, with selected areas of very bright tones around light sources).

Distribution of light in a scene is inevitably quite different at night than it is during the day. It is, of course, much lower in intensity overall, but it also tends to be more constant (and therefore predictable) at night, whereas it may change drastically during the day according to the sun’s movements and the weather. What I wanted to do was to take advantage of the different appearance of scenes at night to defamiliarise them, without succumbing to the temptation to use those differences to romanticise the subjects. In some cases, particularly when there is no visible light source, there is something obviously odd about the lighting, but the night setting is not immediately apparent as such. Later on, I did resort to more chiaroscuro effects, when I was shooting hand-held and fighting against the limitations of the camera and film, but that was a deliberately artificial formal experiment: What can you achieve at the absolute limits of the equipment’s ability to function?

[Discussion continues in this post:]

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