Ambient Lighting provides general, overall illumination that: enables one to move about easily and safely defines the space makes for a comfortable visual environment; General lighting that brightens objects and surfaces in the lower part of the room creates a feeling of warmth and intimacy, whereas indirect lighting, directed to the upper walls and ceiling, gives the space a cooler, quieter, more spacious look.
Accent lighting directs extra light and thus extra attention to selected objects and surfaces. Accent lighting draws the eye, provides dramatic interest, adds excitement. It says, "Look Here!"
Task lighting illuminates areas where work is performed: reading, paper work, food preparation, laundry, games and hobbies. Paper work and reading generally require plentiful, well diffused light coming from over the shoulder or from the side. For kitchen and hobby tasks, a concentrated light from above usually works best.
The amount of light required for good vision depends on three factors:
The age of the people using the lighting the speed and accuracy required the reflectance of the task. Older people require much more light; (at age 55 we need twice as much light to see as well as we did at age 20) they are also much more sensitive to glare, so their lighting must not only be plentiful, but well shielded.
Levels of illumination recommended by the IESNA
In each case a range is indicated; the low value being for young people working on non-critical tasks of high reflectance, (reading large black type on white paper), and the high value being for older persons doing critical work on tasks of poor reflectance (reading the stock market reports or sewing on dark fabric). Passageways 5-10 fc; Conversation 5-10 fc; Grooming 20-50 fc; Reading/Study 20-100 fc; Kitchen Counter/Sink 20-100 fc; Hobbies 50-200 fc
Where to place the lighting
A key element in how to light is where to place the lighting. This is especially important in avoiding glare and veiling reflections. It is also a determining factor in whether a surface texture is to be emphasized or minimized.
The texture of a surface can be "raised" by placing the fixtures close to the surface, so that the lighting strikes it at a grazing angle. If there are unwanted irregularities in the wall, place the fixtures well away from the wall.
In wall washing the surface is illuminated smoothly and evenly top to bottom. Wall washing makes spaces seem larger and is useful for achieving a comfortable level of balanced brightness.