Preserving food, less fighting for food, less roaming to hunt and gather. More stable sense of community. More children. Preserving food, less fighting for food, less roaming to hunt and gather. More stable sense of community. More children.
Contrast sensitivity is the ability of an imaging process to produce an image of objects or tissues in the body that have relatively small physical differences or inherent contrast. The contrast that is to be imaged is in the form of some specific physical characteristic.
It frustrates the eye of a viewer if there is no focal point as the eye is not drawn to any one particular part of the photo. The focal point only occupies a small part of the scene but will make or break the whole image. The simplest form of this is an isolated object seen from a distance on a plain background.