To begin with, the simplest manipulation technique that one could use is shadow making. Shadow making is simply adding or removing a shadow from an object. Although at a glance this may seem an easy task, just adding a shadow to the object in front of you. Don’t be fooled, there is actually a science behind adding and removing shadows and the effect that is created. Without a shadow, there is no visual clue as to the scale and position of the object. The shadow also serves to anchor the object to its surface. Thus creating an impact on how we perceive the image.
By changing the length, direction and depth of the image, we can control how the brain interprets the image. For example adding a short narrow shadow would suggest that is midday, or leaving a space between the object and the shadow to create a levitating effect. Shadows also dictate the lighting in an image. Adding a shadow to facial features also create very important effects. The shadows on a face or an object are important as they give more information about the form and three-dimensional construction. If a face is illuminated by a hard-point source of light, the shadows will be clear. These shadows help to describe the structure and contours of the face more clearly than diffuse light. The direction of light is key to placing the shadow. Everything that faces the light source is bright and everything facing against the light is dark. When applying these laws to facial features you have to be careful, as a cast shadow is usually more elongated then the object itself, so to get the degree of realism that you want placing the right sized and shaped shadow is key.
All in all shadows can be used to serve many purposes, from dictating the height, depth and location of an object in an image to the lighting, brightness and level of contrast that the shadow provides. So what seemed easy at first actually turns out to be a slightly more complicated technique then one might think.