The Scale of Values
128. It is evident that we have in black paint the least quantity of light which we can produce. Black is the lowest of all values. It is equally evident that in white paint we have the greatest possible quantity of light. White is the highest of all values. Mixing Black and White in different proportions we can produce an indefinite number of intermediates. We do not want, however, to be indefinite in our terms; on the contrary we want to be as definite as possible. Let us, therefore, establish, between Black and White, a Middle Value (M); between Black and Middle Value an intermediate Dark (D); between Middle Value and White an intermediate Light (Lt), and between these five values the intermediates, Low Dark (LD), High Dark (HD), Low Light (LLt), and High Light (HLt). Further intermediates (eight) may be established, but to these we need not give any particular names. If we have occasion to refer to any one of them we can say that it lies between certain quantities or values of light for which we have names. We can speak, for example, of the intermediate between Middle and High Dark, and it may be described in writing by the formula M-HD. With this terminology we shall be able to describe the principal quantities or values of light both in speech and in writing.
In order to study the principal quantities or values of light and the possibilities of contrast which they afford it is wise to avoid all differences of color and color-intensity. To do that we produce our Scale of Values in terms of perfect neutrality, in which no color can be distinguished. When we use the names of different values it is understood that they are values of Neutrality. The term M, for example, stands for Neutral Middle, D for Neutral Dark, Lt for Neutral Light.