Human face, symmetry plane

The symmetry plane of the human face is sometimes emphasized by artists (Figure 2-6a-c) while other artists idealize the faces they present (Figure 2-6d-f). Of course, there are minute variations, or even considerable ones as we age, between the left and right sides of the human face (see, e.g., Figure 2-7). Differences between the left and right hemispheres of the brain have been the subject of intensive studies [5],... 

A symmetry operation is the actual event of converting one item into another apparently identical item. This symmetry operation can take place about a point, a line, or a plane of symmetry. Thus, an object is symmetrical when a symmetry operation applied to it gives an object indistinguishable from the original. The point, line or plane about which the symmetry operation is performed is defined as a symmetry element. For example, an axis of symmetry is a symmetry element that describes a line about which all parts of an object are symmetrically disposed. We are all familiar with the vertical reflection plane (or near reflection plane) in the human face. We are also familiar with the sixfold axis of symmetry that lies perpendicular to the plane of a benzene molecule and passes through the center of it (Figure 4.2). 

The word S5mimetry comes from the Greek syn — together — and metron — measure — which tells us that we compare the relation of two or more things to observe symmetry. For example, we associate the word with beauty of the human form by comparing the two parts of the face and body with respect to a mirror plane bisecting our body. Symmetry is also related to the proportions of the various parts of our body with respect to each other. 

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See also in sourсe #XX -- [ ]

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