Scale refers to overall size and proportion refers to relative size. Scale and proportion principles help the viewer organize an image and they can be used to create or minimize points of emphasis. If an object is out-of-scale or oddly proportioned, then it will create a point of emphasis. Also, large scale objects create obvious visual weight. We automatically perceive larger objects as closer and more important than smaller objects.
Proportion also pertains to the design of objects and their placement in the frame. For example, having the focal point dead-center is usually not very interesting, it is usually better placed along one of the "thirds". The ancient Greeks studied mathematics and that it was the controlling force of the universe. From mathematics they derived what they considered to be the ideal proportion - the golden mean or golden section.
For a line, this means that the line is divided such that the ratio of the smaller to the larger part is equal to the ratio of the larger to the entire length of the line. In other words, if the line segment has three points, A, B, and C, such that AB/AC = BC/AB, then it has the proportion of the golden section. This is expressed mathematically by the Fibonacci sequence: 0, 1, 1, 2, 5, 8, 13, 21,..., i.e., Ni = Ni-1 + Ni-2, which gives an increasing ratio of about 1:1.62.
|To create a golden rectangle, let the rectangle have length AC and height AB.|
If we create a set of squares inside the golden rectangle, always adhering to the same proportions, and then inscribe a spiral through these, we get the identical pattern as found in nature for such things as the spiral of a nautilus shell, a cat's claw, a pine cone, flowers, etc. This same spiral can also be constructed by plotting the Fibonacci numbers in sequence about the four axes of a 2D plot.
The golden section has been used extensively in architecture, painting, and sculpture and can be used as a guide for placing edges of objects or lights and shadows.