How to Use Pencil Thumb & String Technique to Judge the Size and Proportions of Subjects/ Objects That You are Drawing

Pencil Measurement.

In drawing all objects, except planes at right angles to the line of direction and the outline of the sphere in any position, the degree of foreshortening that takes place must be somewhat accurately determined. This in Scientific Linear Perspective is determined by optical and mathematical principles.

But in order to get the full educational benefit of a training in Object Drawing, and also because of the usual distance of the object from the spectator, all measurements of apparent positions, directions, and distances must be estimated by the eye. There are, however, some devices that may be used to assist the inexperienced mind through the eye in forming a correct judgment. One of these devices has been called Pencil Measurement, which is explained by the following figure and....

Directions for Pencil Measurement.

1. Hold a pencil or a straight stick in the hand at arm's length between one eye (the other being closed) and the object to be drawn, so that the pencil shall always be at right angles to the line of direction.

2. To do this conveniently, place the thumb and the third and fourth fingers on the side of the pencil next to the body, and the first two fingers on the side of the pencil from the body.

3. The position of the eye must not be changed while taking measurements that are to be compared.

4. For a horizontal measurement, hold the pencil in a horizontal position as above directed, with one end exactly between the eye and one extreme end of the line, or side of the object to be measured, and at the same time move the end of the thumb right or left, on the pencil, until it is exactly even with the other extreme end of the line, or side of the object to be measured.

5. Vertical and oblique measurements are taken in a similar manner, always remembering that the pencil or stick may be revolved by inclining the ends up or down, right or left, but never by bringing one end nearer the eye or the object than the other ; in other words the pencil must always be kept in a plane at right angles to the line of direction.

When the size of the drawing is not important, the actual measurements taken oz the pencil for the height, the width, and other dimensions, may be used on the paper. Usually, however, the size of the drawing depends on the space it is to occupy, or on other conditions, and is to be greater or less than the pencil measurements; in which case the measurements only show the relative proportions of the various dimensions taken.

For instance, if the height of an object measures two and a half inches on the pencil and the width measures only one inch and a quarter, it is plain that the drawing must be made just one half as wide as it is high ; that is, if the drawing is to be three inches high, it must be one inch and one half wide.

Another device for determining the extent of the foreshortening of lines may be called....

String Measurement.

Hold a string of convenient length horizontally, one hand at each end, at arm's length, between one eye and the object, at right angles to the line of direction, and gather the ends of the string between the thumb and the fingers of each hand until the space between the thumbs is just equal to the apparent width of the object ; then hold the string vertically in the same manner, and notice the apparent width of the object as compared with its apparent height as previously measured on the string.

Of course, in both pencil and string measurement, either the height or the width may be measured first ; but it is generally easier to measure the smaller dimension first (especially in pencil measurement), and notice how many times it is contained in the larger.

Some practice is necessary to enable pupils to make reliable pencil or string measurements, but if they carefully follow every direction, they will soon find these devices very useful. Let them first apply these measurements practically to the drawing of plane circles seen obliquely.