A procedure for determining target illuminances

The 10^th edition of the IES Lighting Handbook will contain a new illuminance determination procedure. This article frames these recommendations within an historical context and describes how they are responsive to modern aspects of lighting practice. The new procedure: 1) has more categories with finer steps; 2) provides a method for 1interpreting whether the target value is a minimum, average, or maximum; 3) includes uniformity targets; 4) permits activity levels to be accounted for in outdoor environments; 5) accounts for occupant age; 6) provides a method to adjust photopic illuminance targets for conditions of mesopic adaptation; and 7) accounts for outdoor environmental constraints with the use of lighting zones. This new illuminance determination procedure has been approved by the IES Board of Directors.