PPF (Photosynthetic Photon Flux) is a measure of the total amount of light available for photosynthesis in plants. It is measured in micromoles of photons per second (µmol/s) and indicates how many photons in the PAR spectrum (400-700 nm) a light source emits.
Why is PPF important?
📌 Do not measure the power (Watts), but the amount of usable light for plants .
📌 Determines the efficiency of grow lights in, for example, greenhouses and indoor farming.
📌 Important for plant lighting , because not all light sources are equally effective in photosynthesis.
Difference between PPF, PPFD and DLI
| Term | Meaning | Unit | Application |
|---|---|---|---|
| PPF (Photosynthetic Photon Flux) | Total amount of PAR light emitted by a light source | µmol/s | Amount of light a lamp produces |
| PPFD (Photosynthetic Photon Flux Density) | How much PPF falls on a specific surface | µmol/m²/s | How much light a plant actually receives |
| DLI (Daily Light Integral) | Total PPFD received per day | mol/m²/day | Important for plant growth cycles |
How is PPF measured?
PPF is measured using an integrating sphere , which captures and counts all emitted photons in the PAR spectrum (400-700 nm) . This provides an accurate indication of how well a light source supports plant growth.
Why is PPF a better metric than Watts?
🔹 Watt (W) only measures energy consumption , not light quality.
🔹 PPF (µmol/s) measures how much usable light a lamp actually emits.
🔹 LED lights can have a higher PPF per watt than HPS or fluorescent lights, making them more efficient.
PPF and various grow lights
| Light source | PPF output (average) | Efficiency (µmol/s/W) |
|---|---|---|
| HPS 600W | 1100-1200 µmol/s | ~1.8-2.0 µmol/s/W |
| MH 400W | 700-800 µmol/s | ~1.5 µmol/s/W |
| LED 300W | 600-900 µmol/s | ~2.0-3.5 µmol/s/W |
💡 LED lighting nowadays has a high PPF value with less energy consumption than traditional grow lights.