General service "A" bulbs (in recessed fixtures) provide wide light distribution. "R" and "PAR" bulbs concentrate light. Coverage per fixture is based on providing 15 to 25 footcandles of light. In rooms with darker color use higher wattages.
Number of fixtures needed in a given area: consult ALA showroom experts for manufacturer''s literature. The "spacing ratio" number must be multiplied by the fixture''s mounting height above the lighted area (tabletop, floor, counter, etc.) to give the maximum spacing for even illuminations.
Use the chart to choose the desired light level. Find the spacing (S) for the fixtures. For the required number of fixtures, divide the length of wall by spacing (S). Place the fixtures the same distance from the wall as (S). Example: For Medium Light Level with wall washers with 100W "A" bulbs, five fixtures are needed to wash a 10-foot wall.
Use the chart to select a bulb for the size of beam desired to accent the subject. Light levels range from 20 to 60 foot-candles at the center of the beam. Example: A 2-foot. mounting distance, a 50W "MR-16FL" bulb will cast an 8 x 3-foot beam.
Lighting Can Make a Difference
Basic Types of Lighting
The Shapes and Forms of Lighting
Energy Savings and Efficiency
Designing with Light