The GOLDEN RATIO:
"In mathematics and the arts, two quantities are in the golden ratio if the ratio of the sum of the quantities to the larger quantity is equal to the ratio of the larger quantity to the smaller one. The golden ratio is an irrational mathematical constant, approximately 1.6180339887. Other names frequently used for the golden ratio are the golden section and golden mean. Other terms encountered include extreme and mean ratio, medial section, divine proportion, divine section, golden proportion, golden cut, golden number and mean of Phidias."
"The golden ratio is often denoted by the Greek letter phi. Phidias or Pheidias was an ancient Greek sculptor, painter and architect, who lived in the 5th century BC (480 BC - 430 BC). He is commonly regarded as one of the greatest of all sculptors of Classical Greece and best known for his Statue of Zeus at Olympia, which was one of the Seven Wonders of the Ancient World."
"At least since the Renaissance, many artists and architects have proportioned their works to approximate the golden ratio - especially in the form of the golden rectangle, in which the ratio of the longer side to the shorter is the golden ratio - believing this proportion to be aesthetically pleasing. Mathematicians have studied the golden ratio because of its unique and interesting properties."
The golden ratio is a harmony in which composition, form and structure complements each other. This ratio is evident in nature which we have observed, and incorporated it into art and design. For instance the spiral of a snail shell, the length of a leaf in relation to a branch and the length of a branch in relation to the tree trunk. The same can be said for the human form. It is natures way of ensuring proportion supports efficiency. Of course Biology is the science of exception where mutations and irregularities occur. We humans have attempted to use this ratio for both art and design to either enhance a function or to make appearances more appealing. For instance professional photographers and artist usually incorporate good composition for artistic reasons or to convey an idea or message. This was true of many Renaissance artist such as Leonardo da Vinci, Michelangelo, Raphael and Titian who began to explore the concept of composition.
*(The widescreen format and the 16:9 aspect ratio also follows this golden mean concept which is why widescreen looks so appealing. This is because this format enhances composition and romanticizes the shot more effectively).