The architecture of light: architectural lighting design concepts and techniques. A textbook of procedures and practices for the architect, interior designer and lighting designer pdfdrive com

DIRECTIONAL LIGHT
Directional light is the product of lamps and luminaires that have purpose-built reflectors that harness light from a source and push it out in a single direction.
Figure 9.3 Directional lamps (left) and directional luminaires (right) utilize reflectors and optics to deliver light in a controlled manner.
This effect is often accomplished with an engineered luminaire, or simply within the lamp itself. Directional light is notably delivered in a shape that has distinct boundaries. Our directional light sources create pools and beams and scallops of light that tend to be brightest in the center, and fade to a clear-cut border. These sources are commonly the first ingredient considered in our design process, as they are able to deliver specific pieces of light to specific surfaces and objects in our space. The light arrives from one direction and has a tendency to reflect off of objects in one direction. Hence, directional light creates distinct shadows between light and dark and, therefore, introduces contrast that shows off material texture.
Figure 9.4 Diffuse light sources (top) hide texture and limit contrast. Directional sources (bottom) create shadows, contrast, and visual interest.
We use directional light sources to cast accent onto art, objects and unique architectural features. Directional light makes objects glow and makes metals and glass shimmer and sparkle. It is these sources that add visual interest and hierarchy to environments by creating objects and surfaces that are distinctly brighter than their surroundings. The contrast created by directional light can, however, become uncomfortable over long time periods. Excessive contrast causes the eye to constantly re-adapt when looking from bright elements to dark elements. Directional light is also undesirable for many tasks since excessive shadows (often from a person or his / her own hand) can obscure the task on which you are trying to focus.
DESIGNING WITH DIFFERENT LIGHT TEXTURES
The fundamentals of making good luminaire and lamp decisions are as simple as identifying light sources by the type of light they deliver. The diagram below exhibits what we will consider as the four levels of light texture, ranging from
directional to diffuse.