to be further elaborated
Human vision is far superior to any camera in terms of the range of tones it can encompass within a single field of vision.
Early photographic emulsions were considerably more sensitive to blue light than to other colours on the spectrum of visible light. This meant that landscape photographs, particularly those made on clear days, had completely blown-out skies as the negatives were much denser in the skies than the foreground, resulting in loss of detail in the (positive) print.
Edward Muybridge made a library of clouds and skies that would be layered with a negative where the sky detail was absent in order to make photographs that were nearer to human perception.
The Zone System by Ansel Adams and Fred Archer (1889-1963) is a way to visualise how the tones visible in a scene can most effectively be rendered onto the photographic negative.
Adams (1981, 60) described the zone scale and its relationship to typical scene elements:
| Zone |
Description |
| 0 |
Pure black |
| I |
Near black, with slight tonality but no texture |
| II |
Textured black; the darkest part of the image in which slight detail is recorded |
| III |
Average dark materials and low values showing adequate texture |
| IV |
Average dark foliage, dark stone, or landscape shadows |
| V |
Middle gray: clear north sky; dark skin, average weathered wood |
| VI |
Average Caucasian skin; light stone; shadows on snow in sunlit landscapes |
| VII |
Very light skin; shadows in snow with acute side lighting |
| VIII |
Lightest tone with texture: textured snow |
| IX |
Slight tone without texture; glaring snow |
| X |
Pure white: light sources and specular reflections |
Adams (1981, 52) distinguished among three different exposure scales for the negative:
- The full range from black to white, represented by Zone 0 through Zone X.
- The dynamic range comprising Zone I through Zone IX, which Adams considered to represent the darkest and lightest “useful” negative densities.
- The textural range comprising Zone II through Zone VIII. This range of zones conveys a sense of texture and the recognition of substance.
Adams and Archer sought to refine and better manage some if the many variables that affected exposure, such as developer formulae and development times, so that the photographer could more strictly control the contrast and range of tones rendered.
In reality both film and digital sensors can render many more ‘zones’ than just eleven. But reminds us that when you point a light meter at an object it reads it as mid grey (zone 5). Therefore the photographer has to decide where in the scene they wish Zone V to be in order to control exposure properly.
In colour photography this also needs to be adjusted to allow for the fact that different colours correspond to different tones – yellows are better slightly over-exposed while reds and blues under-exposed.
Exercise 1.8 The Zone System in Practice
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TASK Demonstrate your awareness of the principles of the zone system and your ability to take accurate light readings by producing 3 photographs taken in relatively high dynamic range. The exposure should render as much detail as possible in the brightest and darkest areas of the photograph. Collate these and any reflections.
My reflections on the zone system:
The system sounds simple but in practice is quite complicated because much depends not only on the extreme white and black points where detail needs to be preserved, but the overall balance of dark and light tones that affect perception of clipping and also the desired key of the image for aesthetic reasons. This means that quite a lot of experimentation is needed to select the metering point that will give the desired result.
In digital photography, the important point is the preservation of detail in the image that will be available for post-processing rather than any ‘correct exposure’ in the unreliable LCD screen. It is therefore best to have the highlight clipping warning turned on, and also to review the histograms as one works.
In practice with images of the type of dynamic range I found on the sunniest day in winter, I could adjust both highlights in images exposed for the shadows and shadows in images exposed for the highlights equally easily to regain detail where I wanted them.
The zone system is certainly a useful guide, but will require a lot of practice to gain real confidence. Alternative methods are auto-bracketing, or using the camera’s matrix metering system together with the highlight clipping warning and exposure compensation where necessary. These two are arguably quicker unless I get really confident.
The Images
These images were taken along the river Cam on a sunny day. All the images had both slight black and slight white clipping and were just outside the Dynamic Range of my camera. I used Spot metering and experimented with different metering points to try and reflect the image I had in mind.
Image 1: Graffiti
In Graffiti my interest was in maintaining detail in the sunlight on the silver graffiti rather than the dark bridge.
My first attempt took as mid grey the bright grass at the back assuming this was a mid-tone. But this image was much lighter than I wanted with too much clipping on the graffiti and very washed-out. Although the grass was mid-tone for the image as a whole, it was not mid-tone for the image I wanted.
My second attempt took the lighter path as the mid-tone. This then pushed all the other tones darker, giving me more detail on the graffiti.
In post-processing in Lightroom I found though that there was not much difference in what I could do with the image – adjusting the highlights, shadows, exposure and contrast I could achieve pretty much the same effect with either image.
Image 2: Bridge
In this image I wanted to highlight the dot of the duck and I was also interested in the white detail and reflections of the V shapes. Again I was not so interested in the shadows except as background contrast.
This second image was also just outside the dynamic range of my camera with both slight black and white clipping. But because the very white area takes up less of the image, choosing the grass as mid grey worked better because the smaller area of highlight clipping is less noticeable. I took further shots using the water, but that lightened the image too much. Metering from the lighter sky at the back became too dark.
Image 3: Wier
In this third image the dynamic range was not as great as it first appeared except for some bright sparkles on the water. The blacks were just within range. The image on the left was spot metered on the water, pushing everything too dark – the spot metre picked up the very tiny bright sparkles rather than the larger grey areas between. The second image I metered on the white water bottom left giving a wider tonal range.
