This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Artistic Bisection Of A Line. In order that you may understand more clearly why a subject should be located either to right or left of the center, or above or below the center of a picture, we will go into detail regarding the dividing of a straight line in the proportions which will give the most pleasing effect.
227. In Figure 32 is illustrated a series of straight lines divided by short cross lines. Look at these lines carefully and you will probably feel that the lines A, B and C are divided in a more pleasing manner than F, G and H. In other words, if a straight vertical line is to be divided into two unequal parts, you prefer to have the division come above the middle. This is not an altogether unimportant fact.
228. In judging vertical distances, we almost always over-estimate the upper half. For this reason the line E, which is divided into two equal parts, appears to be divided into two slightly unequal parts, and the lower section seems to be the smaller. The line D is divided at a point slightly above the middle, but it appears to be divided into two exactly equal parts. Many persons would say that the line D is more pleasing than E, for D appears to be divided into two equal parts, while E appears as if an unsuccessful attempt had been made to divide the line into two equal parts.
229. Line D appears to be perfectly symmetrical - its two parts appear equal. The symmetry about this division pleases us, and most persons would say that this line, which is divided symmetrically, is more pleasing than A or H, which' are not divided symmetrically.
230. The two parts of the lines A, B, G and H appear too unequal, and the two parts of line E appear too nearly equal. Lines C and F are very pleasing. They have divisions which do not seem to be too much alike, so the divisions give diversity. The parts are not so different that they destroy the feeling of unity in the line. A line is pleasing if its two parts are not too much alike and not too different. The ratio of the smaller section of the line to the larger section in C and F is approximately that of 3 to 5. That is to say, if a vertical line is eight inches long, the result is pleasing if the line is divided into two sections which are respectively 3 and 5 inches long.
231. Exact experimentation and measurements of artistic productions show that there is a reasonable preference for this ratio, which is known as the "golden section." The exact ratio is that of 1 to 1.618, which is approximately that of 3 to 5. A line is divided most artistically if the lower section is 1.618 times as great as the upper. Although the fraction seems very formidable, it is the arithmetical expression of a simple proportion, which is this: The short section is to the longer section as the longer section is to the sum of both sections. Any division of a line which approximates this "golden section" is pleasing, but a division which approximates the symmetrical division (and is not quite symmetrical) is displeasing. This explains why the principal object of importance in a picture should not be placed in the center of the picture space.
232. If you hold Figure 32 sideways, the lines will be changed from vertical to horizontal. The divisions will now assume a new relation. The divisions of lines A, B and C cease to be more pleasing than those of F, G and H. This shows why the main subject of a picture looks more pleasing on the left side. E now seems to be divided symmetrically and is more pleasing than D. In fact, for most persons the symmetrical divisions of E seem to be more pleasing than those of even C and F, which are divided according to the ratio of the "golden section." The most pleasing division of a horizontal line is that of perfect symmetry, and the next most pleasing is that of the "golden section."
233. In these divisions of straight lines into two equal parts, unity is secured; in the divisions according to the ratio of the "golden section" diversity is secured, but the unity is not entirely lost. Unity and diversity are essential elements in all esthetic pleasures. In vertical lines we seem to prefer the emphasis on the diversity, while in horizontal lines the exact symmetry, or unity, is most pleasing.
Illustration No. 33 Masses of Equal Size See Paragraph No. 237.
Illustration No. 34 Masses of Unequal Size See Paragraph No. 237.
234. In arranging your picture properly on the ground-glass, as well as in selecting the point of view, it is essential that you always bear in mind the principle of the steelyard. It is quite true that there are excellent pictures that do not possess this principle, but there are, in such pictures, other qualifications which take the place of the steelyard principle.