Lighting Terminology 1 PATRICK DAVIS, ORION ENERGY SYSTEMS

Terms Lumen Footcandle (H&V) Efficacy Rated Lamp Life Lumen maintenance/ Lumen depreciation Color temperature Color rendering index 2

Concept: Lawn Sprinklers Sprinkler output vs. water reaching grass 3

New Term: Lumen Measure of the strength of light radiating from a light source measured at the source (Output) Measured in lumens 4

New Term: Foot Candle A measure of the intensity of light falling on a square foot of working surface 1fc = 1 lumen per ft 2 5

1 Foot Candle = 1 lumen/ft ft 2 1 Lumen

3 Foot Candles = 3 lumen/ft ft 2

Foot Candle Measurements Factors affecting… ◦Sensor distance from source ◦Ambient light ◦Location relative to fixture(s) ◦(e.g. directly under, off to one side) ◦Meter accuracy ◦Shirt color 8

Horizontal Foot Candle Example 9 Measured on a horizontal plane such as desk/workbench

Vertical Foot Candle Example 10 Measured on a vertical plane E.g., Items on pallet racking; book shelf

New Term: Efficacy Amount of light (lumens) output by a lamp per watt of electrical energy input ◦= Lumens watts Think “miles per gallon” ◦= Miles/gallon 11

New Term: Rated Lamp Lifetime Manufacturer’s rating RLL = the number of hours a sample of lamps will operate before half the lamps burn out 12

Fact: ALL light sources get dimmer with age 13

Fact: Some technologies are better than others 14

New Term: Lumen Maintenance Measure of how well a lamp maintains its rated light output as it ages ◦1 st Measure after 100 hour “burn-in” period ◦2 nd Measure after 40% of rated life 15

Lumen Maintenance All lamps are not created equal… Some types are better than others 16 % of initial lumens 40%

New Term: Lumen Depreciation 35% lumen depreciation 17 % of initial lumens 40% 65% lumen maintenance

18 Color Qualities

New Term: Color Temperature A measurement of the warmth or coolness of a lamp ◦Measured in Degrees Kelvin (°K) ◦Affects how we see and feel 19

Color Temperature ºK 86 CRI 2100 ºK 25 CRI 2100 ºK 25 CRI Blue light w violet overtones Blue light w light violet overtones White light with blue color White light with blue overtones All white light with little blue color White light with yellow overtones White light with yellow color Yellow light

LED Color Temperature 21

New Term: Color-Rendering Index (CRI) 22 0 – 100 scale Indicates how perceived colors match actual colors ◦100 = best ◦0 = worst

Questions 23