Selected Bibliography Architectural Graphics | Page 133

CREATING TONAL VALUES Using the traditional media of pencil and pen-andink to make dark marks on a light surface. there are several basic techniques for creating tonal values. • • • • Hatching Crosshatching Scribbling Stippling These shading techniques all require agradual building up or layering of strokes or dots. T visual he effect of each technique varies according to the nature of t he stroke, the medium. and the texture of the drawing surface. Regardless of the shading technique we use, we must always be fully aware of the tonal value being depicted. • Because tonal value is expressed primarily through t he relative proportion of light to dark areas on t hedrawing surface. the most important characteristicof these techniques is the spacing and density of the strokes or dots. • The law of simultaneous contrast states that the stimulation of one tonal value is projected instantaneously on ajuxtaposed value. For example, atonal valuesuperimposed upon a darker tone will appear lighter than the same value set against a lighter tone. • Secondary characteristics include the visual texture. grain, and direction of the strokes. • When rendering the darkest values, we should be careful n to ot lose the white of the paper. Covering the paper surface entirely can cause adrawing to lose depth and vitality Digital Tonal Values Paint and drawing programs usually permit colors and tonal values to be selected from amenu or palette. Image-processing software further allows the creation and application of visual textures. some of which mimic the traditional techniques outlined onthe following pages. RENDERING TONAl VALUES/ 127