The Zone System

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

 

Colour Photography

Wikipedia to be properly edited with links
Main article: Color photography

Color photography was possible long before Kodachrome, as this 1903 portrait by Sarah Angelina Aclanddemonstrates, but in its earliest years the need for special equipment, long exposures and complicated printing processes made it extremely rare.

A photographic darkroom withsafelight

Color photography was explored beginning in the mid-19th century. Early experiments in color required extremely long exposures (hours or days for camera images) and could not “fix” the photograph to prevent the color from quickly fading when exposed to white light.

The first permanent color photograph was taken in 1861 using the three-color-separation principle first published by physicist James Clerk Maxwell in 1855. Maxwell’s idea was to take three separate black-and-white photographs through red, green and blue filters. This provides the photographer with the three basic channels required to recreate a color image.

Transparent prints of the images could be projected through similar color filters and superimposed on the projection screen, an additive method of color reproduction. A color print on paper could be produced by superimposing carbon prints of the three images made in their complementary colors, a subtractive method of color reproduction pioneered by Louis Ducos du Hauronin the late 1860s.

Russian photographer Sergei Mikhailovich Prokudin-Gorskii made extensive use of this color separation technique, employing a special camera which successively exposed the three color-filtered images on different parts of an oblong plate. Because his exposures were not simultaneous, unsteady subjects exhibited color “fringes” or, if rapidly moving through the scene, appeared as brightly colored ghosts in the resulting projected or printed images.

Implementation of color photography was hindered by the limited sensitivity of early photographic materials, which were mostly sensitive to blue, only slightly sensitive to green, and virtually insensitive to red. The discovery of dye sensitization by photochemist Hermann Vogel in 1873 suddenly made it possible to add sensitivity to green, yellow and even red. Improved color sensitizers and ongoing improvements in the overall sensitivity of emulsions steadily reduced the once-prohibitive long exposure times required for color, bringing it ever closer to commercial viability.

Autochrome, the first commercially successful color process, was introduced by the Lumière brothers in 1907. Autochrome plates incorporated a mosaic color filter layer made of dyed grains of potato starch, which allowed the three color components to be recorded as adjacent microscopic image fragments. After an Autochrome plate was reversal processed to produce a positive transparency, the starch grains served to illuminate each fragment with the correct color and the tiny colored points blended together in the eye, synthesizing the color of the subject by the additive method. Autochrome plates were one of several varieties of additive color screen plates and films marketed between the 1890s and the 1950s.

Kodachrome, the first modern “integral tripack” (or “monopack”) color film, was introduced by Kodak in 1935. It captured the three color components in a multilayer emulsion. One layer was sensitized to record the red-dominated part of the spectrum, another layer recorded only the green part and a third recorded only the blue. Without special film processing, the result would simply be three superimposed black-and-white images, but complementary cyan, magenta, and yellow dye images were created in those layers by adding color couplers during a complex processing procedure.

Agfa’s similarly structured Agfacolor Neu was introduced in 1936. Unlike Kodachrome, the color couplers in Agfacolor Neu were incorporated into the emulsion layers during manufacture, which greatly simplified the processing. Currently available color films still employ a multilayer emulsion and the same principles, most closely resembling Agfa’s product.

Instant color film, used in a special camera which yielded a unique finished color print only a minute or two after the exposure, was introduced by Polaroid in 1963.

Color photography may form images as positive transparencies, which can be used in a slide projector, or as color negatives intended for use in creating positive color enlargements on specially coated paper. The latter is now the most common form of film (non-digital) color photography owing to the introduction of automated photo printing equipment.