# Conversion - PPFD to Foot-candles

PPFD (µmol m-2 s-1) to Foot-candles

Light SourceConversion Factor
Sunlight 5.01
Cool White Fluorescent Lamps 6.87
Mogul Base High Pressure Sodium Lamps 7.62
Dual-Ended High Pressure Sodium (DEHPS): ePapillion 1000 W 7.11
Metal Halide 6.60
Ceramic Metal Halide (CMH942): standard 4200 K color temperature 6.01
Ceramic Metal Halide (CMH930-Agro): 3100 K color temperature, spectrum shifted to red wavelengths 5.45
Low Pressure Sodium Lamp (monochromatic at 589 nm) 9.85
Multiply the PPFD by the conversion factor to get foot-candles. For example, full sunlight is 2000 μmol m-2 s-1 or 10,020 foot-candles (2000 ∗ 5.01).

Foot-candles to PPFD (µmol m-2 s-1)

Light SourceCalibration Factor
Sunlight 0.200
Cool White Fluorescent Lamps 0.146
Mogul Base High Pressure Sodium Lamps 0.131
Dual-Ended High Pressure Sodium (DEHPS): ePapillion 1000 W 0.141
Metal Halide 0.152
Ceramic Metal Halide (CMH942): standard 4200 K color temperature 0.167
Ceramic Metal Halide (CMH930-Agro): 3100 K color temperature, spectrum shifted to red wavelengths 0.184
Low Pressure Sodium Lamp (monochromatic at 589 nm) 0.102
Multiply the foot-candles by the conversion factor to get PPFD. For example, full sunlight is 10,020 foot-candles or 2000 μmol m-2 s-1 (10,020 ∗ 0.2).

### PPFD to Foot-candle Reference Table

Sunlight

If PPFD is:then, fc is:
10 50.1
100 501
200 1002
300 1503
600 3006
1000 5010
*2000 *10,020
*Full sunlight at solar noon or on a clear summer day.

Cool White Fluorescent

If PPFD is:then; fc is:
10 68.7
100 687
200 1374
300 2061
600 4122
1000 6870
2000 13,740

### Photometric Units, Illuminance

Foot-candle: one lumen per square foot. The 16th General Conference on Weights an Measures (CGPM), Oct. 1979, decided that the candela is the luminous intensity of a source emitting monochromatic radiation of frequency 540 x 1012 Hz and radiant intensity 1/683 watt per steradian. This corresponds to 683 lumens per watt of radiation at approximately 555 nm wavelength, which is near the maximum of the standard photopic spectral luminous efficiency curve.

LUX: one lumen per square meter; differs from foot-candle by about a factor of 10.

### Quantum Units, Photon Flux Density

Microeinstein: per second and square meter (µE m-2 s-1). The einstein has been used to represent the quantity of radiant energy in Avogadro's number of photons and also Avogadro's number of photons. The second definition has the einstein equal a mole of photons. While commonly used as a unit for photosynthetically active radiation (PAR), the einstein is not an SI unit.

Micromole: per second and square meter (µmol m-2 s-1). This term is based on the number of photons in a certain waveband incident per unit time (s) on a unit area (m2) divided by the Avogadro constant (6.022 x 1023 mol-1). It is used commonly to describe PAR in the 400-700 nm waveband.

Definition Source: Thimijan, Richard W., and Royal D. Heins. 1982. Photometric, Radiometric, and Quantum Light Units of Measure: A Review of Procedures for Interconversion. HortScience 18:818-822.