ABSTRACT
THE ZONE SYSTEM, HISTOGRAMS, AND ISOS One of the tools to shape the ratio of light and shadow revolves around the zone scale-an arbitrary scale indicating the tonal values from dark to light in an 11-step black-grey-white gradation, numbered 0-10 (0 = black; 10 = white; see Figure 3.1 ). Zones 0-3 represent black and deep shadow values (details and texture in an image can begin to be seen in zone 2, while 3 shows dark details and some texture, and 4 reveals landscape shadows and dark foliage). In addition, zones 4-6 represent face tones (from dark-skinned to Caucasian facial tones). The mid-gray of 5 represents brown skin tones and sky; this is also the value of an 18% gray card used for white balance. Zones 7-9 hit lighter greys and highlights (an 8 would reveal texture in snow, whereas 9 would represent blown-out highlights, and 10, pure white). Each zone number indicates a doubling in brightness from the previous zone; the gray in 6 is twice as bright as the gray in 5; the gray in 7 is four times brighter than 5 (each step is a multiple of two). The black in 1 is half as bright as in 2. The doubling and halving of the grey scale is similar to the doubling and halving of the exposure range in f-stops.
