Michel Jacobs on Portrait Painting Using Dynamic Symmetry (the Root 2 Dynamic Symmetry rectangle) From the book Colour in Portrait Painting
There are certain roots generally used in Dynamic Symmetry which suggests the size of the well-proportioned canvas. But it is not necessary to have a portrait always in a stated root. These forms are used in Dynamic Symmetry because they are in proportion and are pleasing to the eye. I find a canvas about 25 by 30 inches about the right size for a head and shoulders and one about 36 by 48 inches for a three-quarter length. These are approximately root two in Dynamic Symmetry. With a full-length figure standing, it would depend on the height of the person: when the entire canvas forms two squares, for example, it would be in a root four.
I have reproduced on page 24 illustrations from my previous book to show a number of different roots and their use.
These diagrams should be drawn on a small board in the sample proportion as the large picture, say about one-tenth the size of what the portrait is going to be. The diagram can be drawn in with pencil and the whole composition planned in the small size of the cardboard. When making this cardboard sketch, you do not need the model to sit for you. This sketch is done only to visualize what you propose to do on the large canvas. This cardboard sketch can be colored in the colors you propose to paint the picture. It is a very good idea to show your sitter what colors and composition you are going to use. This would be a miniature of the larger picture, without any detail or portrait - just a spot of flesh color for the head and hands, and the drapery and background painted in roughly.
As a matter of fact, it is a good idea to make two or three of these small sketches, say about four or five inches from which the sitter may choose the one liked best.
It is not necessary to have the lines of a portrait follow all the Dynamic Symmetry lines, only some of them. But the principal point of interest which would be the head should be drawn in where the diagonal and the crossing lines meet.
The lines of the drapery or clothing should follow more or less the rhythm of the Dynamic Symmetry. Remember, this is not an architectural drawing, the artist has a certain amount of license, and the painting is not hard and fast.
Try to get as much rhythm into the composition as possible. See that the balance and weight gives a solidity and restful impression. Hogarth had what he called, "lines of grace and beauty," which were a double curve. Then there is the spiral, which is a more or less circular form leading to the principal point of interest, the head.
To have good rhythm, it is well to repeat a form in larger and smaller dimensions. Take, for example, a form the shape of an egg. This egg form should be repeated two or three times in a picture. Even the background making the outer forms can be repeated in the same shape around the figure by a manipulation of the background, drapery, or costume. The trajectory of a bullet forms a parabolic curve, a form of rhythm very often used.
The letter S (printed) gives you a very good idea of a rhythmic curve. In other words, think of rhythm as a symphony, one form relating to another. This idea of rhythm can be carried out also in color and in values. Dynamic Symmetry will help with the lines and masses, relating one to another. Paraphrasing an old adage, let us say, "Great big forms have little forms within their forms to light them, and little forms have lesser forms and so ad infinitum."