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Graphite Portrait Drawing—Value And Form In Relation To Tone

December 26th, 2008 · No Comments

Value and form – are two of the four elements of drawing. The other two are line and texture.

In this article we will discuss the notion of plasticity or tone and how it relates to the concepts of value and form.

Plasticity or tone – is the visual push and pull of lights and darks which, when presented in a interconnected and harmonious whole, defines the 3-dimensional forms of a portrait.

The human eye can discriminate between many more values than the 12 we usually employ in a drawing. That means that the artist must “deceive” the eye into believing that it is seeing more than is actually on the drawing paper. To this end we must understand how light behaves and values are observed.

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 complaining if the plasticity is harmonious. Only then will the viewer emotionally engage.

The subject of creating harmonious plasticity is extensive. In this article we limit ourselves to realistic portraiture.

* Values – are just degrees of darkness and lightness. We usually restrict ourselves to 12 discrete values.

To understand how a form is rendered we need to understand how light behaves and how values enter into this. There are 2 properties of light relevant to drawing:

(1) Light travels in a straight line and bounces off surfaces.

(2) The intensity of light diminishes quickly with distance.

From these characteristics it follows that:

* As a shape turns away from the light source it darkens.

* When two planes face the light they will attain dissimilar values if their distances from the light source are different. For example, the cheek closest to the light source will have a lighter value than the one further away.

* The lightest value on a form is the “highlight”. The highlight is invariably on a plane that is directly facing the light source.

* The bulk of a portrait’s value is so-called half-tone. That is, anything in-between pure white and pure black. Halftone rendering is simultaneously the most enjoyable and the most annoying aspect of drawing.

* As a form turns fully away from the light source it gradually 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 surface onto another. Recall that light bounces off surfaces but with reduced intensity. So be careful not to overstate your reflected light.

* There is also the peak of the shadow which is the darkest value on the form. This band of darkness lies between the darkest halftones and the reflected light. This band of darkness is called the Line of Appelle. It is important to capture its shape correctly because it determines the form’s volume.

* As a form turns away from the light, the halftone plane changes have a soft edge. The quality of this edge is determined by several factors the most important of which are the degree of plane change, the intensity of the light source, 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 shape onto another. An illustration is the shadow that is cast by the nose onto the cheek.

An excellent exercise for understanding the notion of tone is to draw a white egg. For a more controlled 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 pollute the situation.

In conclusion, the use of the 12-value scale together with the above guidelines allows you to produce the necessary plasticity or tone for your subject.

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