CREATING DEPTH ON A 2-DIMENSIONAL SURFACE
The television picture tube is a two dimensional surface that attempts to recreate the three dimensional world around us. The dimensions of height and width are physical components of the picture tube. The third dimension, depth, must be created within the picture. Lighting plays a major role in creating the illusion of this third dimension. The size, perspective and clarity of an object also play a role in creating a third dimension. The following examples show how a two dimensional circle can be transformed into a three dimensional ball using some basic lighting principles.

Fig.1 Flat	Fig.2 Shading	Fig.3 Highlight	Fig.4 Shadow

Illustrates a ball in a two dimensional world; the ball has height and width only. The red of the ball can be referred to as the base tonal value of the object. This "flat" ball represents a three dimensional surface being lit directly from the camera lens angle. This style of lighting creates a flat appearance of an object.

We perceive dark portions of an object as being further away from us, while lighter portions appear closer. Shading one side of the ball, by placing the main light high and to the left of the camera lens, creates a dark shadow area that is perceived to be further away than the lighter area of the ball. The shadow's transition (the edge between the base tonal value of the object and the darkness of the shadow) will vary with the type of main light source used. A soft light will create a wide shadow edge with a gradation between the base tonal value and the darkest portion of the shadow. A hard light will create a defined shadow edge with very little gradation between the base tonal value and the darkness of the shadow. A Lighting Director's choice between a hard or soft light source, as the main light source, will influence the degree of gradation between base tonal value and the darkness of the shadow.

An objects highlight (the reflection of the originating light source within the object) gives an indication to the surface texture of that object. Like the shadow edge, the highlight's edge will have a transition from the object's base tonal value to the brightest portion of the highlight. The highlight's transition edge will be wide when the object's surface has a matte or rough finish. When the surface has a polished smooth finish, the highlight edge can be sharp with little or no transition between tonal value and the bright portion of the highlight. The polished smooth surface acts like a mirror reflecting the exact shape of the originating light source. In this example, if the ball's surface were polished smooth and the main light source was a window, the highlight would show a reflection of the exact square shape of the window.

The object itself must cast a shadow to show its spatial relationship to the world around it. The ball's shadow in this example gives the impression it is sitting on a surface. The lack of an object shadow, as in figure three, gives the impression the ball is floating in space without any relationship to its surroundings. The object's shadow edge will also have a transition between the darkest portion of the shadow and the lighter portion of the surface it is cast upon. Again the width of this shadow edge transition will be determined by the type of main light source, hard or soft light, and the distance the main source is from the object. A soft light source creates a wide shadow edge transition while a hard light creates a narrow shadow edge transition. A light placed close to the object creates a wider shadow transition than a light placed further away from the object. The length of the object's shadow will relate to the placement of the main light source. In this example, had the main light source been placed to the bottom left of the ball, the shadow would have been longer. The highlight will also reposition itself within the object when the main light source is moved.

Article by Brad Dickson - STLD Canada