Category | Type | Overall luminous efficacy (lm/W) |
Overall luminous efficiency |
---|---|---|---|
Combustion | Candle | 0.3 | 0.04% |
Gas mantle | 1–2 | 0.15–0.3% | |
Incandescent | 15, 40, 100W tungsten incandescent (230 V) | 8.0, 10.4, 13.8 | 1.2, 1.5, 2.0% |
5, 40, 100W tungsten incandescent (120 V) | 5, 12.6, 17.5 | 0.7, 1.8, 2.6% | |
Halogen incandescent | 100, 200, 500W tungsten halogen (230 V) | 16.7, 17.6, 19.8 | 2.4, 2.6, 2.9% |
2.6W tungsten halogen (5.2 V) | 19.2 | 2.8% | |
Halogen-IR (120 V) | 17.7–24.5 | 2.6–3.5% | |
Tungsten quartz halogen (12–24 V) | 24 | 3.5% | |
Photographic and projection lamps | 35 | 5.1% | |
Light-emitting diode | LED screw base lamp (120 V) | Up to 102 | Up to 14.9% |
11W LED screw base lamp (230V) | 138 | 20.3% | |
21.5W LED retrofit for T8 fluorescent tube (230V) | 172 | 25% | |
Theoretical limit for a white LED with phosphorescence color mixing | 260–300 | 38.1–43.9% | |
Arc lamp | Carbon arc lamp | 2–7 | 0.29–1.0% |
Xenon arc lamp | 30–50 | 4.4–7.3% | |
Mercury-xenon arc lamp | 50–55 | 7.3–8% | |
Ultra-high-pressure (UHP) mercury-vapor arc lamp, free mounted | 58–78 | 8.5–11.4% | |
Ultra-high-pressure (UHP) mercury-vapor arc lamp, with reflector for projectors | 30–50 | 4.4–7.3% | |
Fluorescent | 32W T12 tube with magnetic ballast | 60 | 9% |
9–32W compact fluorescent (with ballast) | 46–75 | 8–11.45% | |
T8 tube with electronic ballast | 80–100 | 12–15% | |
PL-S 11W U-tube, excluding ballast loss | 82 | 12% | |
T5 tube | 70–104.2 | 10–15.63% | |
70–150W inductively-coupled electrodeless lighting system | 71–84 | 10–12% | |
Gas discharge | 1400W sulfur lamp | 100 | 15% |
Metal halide lamp | 65–115 | 9.5–17% | |
High-pressure sodium lamp | 85–150 | 12–22% | |
Low-pressure sodium lamp | 100–200 | 15–29% | |
Plasma display panel | 2–10 | 0.3–1.5% | |
Cathodoluminescence | Electron stimulated luminescence | 30 | 5% |
Ideal sources | Truncated 5800 K black-body | 251 | 37% |
Green light at 540 THz (maximum possible luminous efficacy by definition) | 683 | 100% |
Sources that depend on thermal emission from a solid filament, such as incandescent light bulbs, tend to have low overall efficacy because, as explained by Donald L. Klipstein, “An ideal thermal radiator produces visible light most efficiently at temperatures around 6300 °C (6600 K or 11,500 °F). Even at this high temperature, a lot of the radiation is either infrared or ultraviolet, and the theoretical luminous [efficacy] is 95 lumens per watt. No substance is solid and usable as a light bulb filament at temperatures anywhere close to this. The surface of the sun is not quite that hot. At temperatures where the tungsten filament of an ordinary light bulb remains solid (below 3683 kelvin).
SI photometry units
Quantity | Unit | Dimension | Notes | ||
---|---|---|---|---|---|
Name | Symbol | Name | Symbol | Symbol | |
Luminous energy | Qv | lumen second | lm⋅s | T⋅J | The lumen second is sometimes called the talbot. |
Luminous flux, luminous power | Φv | lumen (= candela steradians) | lm (= cd⋅sr) | J | Luminous energy per unit time |
Luminous intensity | Iv | candela (= lumen per steradian) | cd (= lm/sr) | J | Luminous flux per unit solid angle |
Luminance | Lv | candela per square metre | cd/m2 | L−2⋅J | Luminous flux per unit solid angle per unit projected source area. The candela per square metre is sometimes called the nit. |
Illuminance | Ev | lux (= lumen per square metre) | lx (= lm/m2) | L−2⋅J | Luminous flux incident on a surface |
Luminous exitance, luminous emittance | Mv | lux | lx | L−2⋅J | Luminous flux emitted from a surface |
Luminous exposure | Hv | lux second | lx⋅s | L−2⋅T⋅J | Time-integrated illuminance |
Luminous energy density | ωv | lumen second per cubic metre | lm⋅s/m3 | L−3⋅T⋅J | |
Luminous efficiency (of radiation) | K | lumen per watt | lm/W | M−1⋅L−2⋅T3⋅J | Ratio of luminous flux to radiant flux |
Luminous efficiency (of a source) | η | lumen per watt | lm/W | M−1⋅L−2⋅T3⋅J | Ratio of luminous flux to power consumption |
Luminous efficiency, luminous coefficient | V | 1 | Luminous efficacy normalized by the maximum possible efficacy |