AN INTRODUCTION TO TESNovember 7, 2008

Color Rendering

Presented By: Sarah DouglassSeptember 30, 2011

Color Rendering

• Color rendering is the effect of a light source on the color appearance of objects by comparison with their appearance under a reference light source

• Reference sources have a Color Rendering Index of 100

• CRI ranges from 0 (worst) to 100 (best)• Low CRI sources are cheap to operate but give off low

quality light• High CRI sources cost more to operate but have higher

quality light

Color Rendering of Daylight

Types of Light Sources

1. Incandescent2. Halogen3. Fluorescent4. Mercury5. Metal Halide6. High Pressure Sodium7. Low Pressure Sodium

Incandescent

• Tungsten filament heated to a high temperature, causing it to glow

• Bulb protects the filament from air to reduce the rate of tungsten evaporation

• CRI = 100

Halogen

• Incandescent lamp filled with halogen gas• Higher operating temperature• Dimmable• CRI = 100

Fluorescent

• Cathode creates current• Mercury droplets radiate UV radiation• Phosphor coating produces light due to the UV radiation• Different phosphors affect the output spectrum• CRI = 50-85

Mercury

• Lamp has UV radiation emissions• At high pressure, mercury gas re-emits radiation as light• Emission is concentrated in 5 narrow bands• CRI = 17-49

Metal Halide

• Metal halides are added to mercury lamps (thallium, indium, sodium iodide)

• Improves color quality• CRI = 85

Low Pressure Sodium

• When turned on, small current passes through the sodium in the bulb, giving off a faint red discharge

• When the sodium evaporates, the resulting vapor produces a yellow emission

• Used almost solely for street lighting• CRI = 5

High Pressure Sodium

• Not as efficient as low pressure sodium lamps• Radiate energy across the visible spectrum• CRI = 24

`

Common Light Source Indexes

Type of Light Source CRI

Low Pressure Sodium5

Clear Mercury 17

High Pressure Sodium 24

Coated Mercury 49

Standard Fluorescent 50-70

Metal Halide 85

Triphospher Fluorescent 85

Incandescent/Halogen 100

Interactive Color Booth