* Value and Form - are 2 of the four essentials of drawing. The other 2 are line and texture.
In this expose we will discuss the concept of flexibility and how it relates to the ideas of tone and form.
* Elasticity - is the visual push and pull of lights and darks which, when presented in a united whole, defines the 3-dimensional shapes of a portrait.
The human eye can distinguish between many more tone than the 12 we ordinarily employ in a drawing. That means that the artist must "trick" the eye into believing that it is seeing more than is actually on the drawing paper. To this end we must appreciatehow light behaves and tones are perceived.
The trick is to manipulate the eye's natural tendency towards closure, i.e., towards finishing a drawing even if parts are not actually there. But the eye only does that without protest if the flexibility is harmonious. Only then will the viewer emotionally connect.
The subject of creating harmonious flexibility is far-reaching. In this expose we limit ourselves to realistic portraiture.
* Tones|Values - are just degrees of darkness and lightness. We ordinarily limit ourselves to 12 separate tones.
To appreciate how a form is rendered we need to appreciate how light operates and how tones enter into this. There are 2 characteristics of light pertinent to drawing:
(1) Light travels in a straight line and reflects off surfaces.
(2) The intensity of light diminishes quickly with distance.
From these characteristics it follows that:
* As a form turns away from the light source it dims.
* When two planes face the light they will acquire different tones if their distances from the light source are different. For instance, the cheek closest to the light source will have a lighter tone than the one which is farther away.
* The lightest light on a form is the "highlight". The highlight is invariably on a face that is directly facing the light source.
* Most of a portrait’s tone is so-called halftone. That is, anything in-between pure white and pure black. Halftone rendering is simultaneously the most fun and the most frustrating part of drawing.
* As a form turns fully away from the light source it increasingly descends into shadow, towards totally black (i.e., the absence of light). However, there is more to it.
* There is also reflected light from one plane onto another. Remember, light reflects off surfaces but with reduced intensity. So be cautious not to overstate your reflected light.
* There is also the crest of the shadow which is the darkest value on the form. This band of darkness lies between the darkest half-tones and the reflected light. This band of darkness is called the Line-of-Appelle. It is essential to capture its shape accurately because it determines the form’s volume.
* As a form turns away from the light, the half-tone plane changes have a soft edge. The quality of this edge is determined by several factors the most essential of which are the amount of plane change, the intensity of light, and the texture of the surface.
* In portrait drawing there are also cast shadows which are hard-edged and very dark and are cast by one form upon another. An example is the one that is cast by the nose onto the cheek.
A very good exercise for appreciating the concept of flexibility is to sketch a white egg. For a more proscribed situation you can build yourself a black box with one side open that fully controls the light of one source and blocks out the light of other sources that could disturb the situation.
In closing, the use of the 12-value scale together with the above tips allows you to produce the necessary flexibility for your subjects.
