What’s the difference between PPFD and LUX in grow lamps for plants?
Why should we focus on PPFD rather than LUX when testing grow lamps for plants?
Let’s start by explaining what PPFD and LUX are.
1. What is PPFD?
PPFD stands for Photosynthetic Photon Flux Density. It measures how many photons usable for photosynthesis a plant receives per second over a square meter.
It sounds technical, but in simpler terms, it tells you how much useful energy the plant is actually absorbing from the light source.
The higher the PPFD, the more energy the plant can absorb, promoting photosynthesis. So, is a higher PPFD always better?
Not necessarily. Here, two key points come into play—the light saturation point and the light compensation point.
The light saturation point is like the "ceiling" for a plant’s photosynthesis. Once this point is reached, increasing the light won’t improve the plant’s photosynthesis efficiency.
On the other hand, the light compensation point is the minimum light the plant needs to survive. Below this point, the plant can’t even absorb enough light energy to sustain itself.
When buying a grow lamp, you can’t just look at the PPFD number. You need to know how much light your specific plant needs to choose the right grow lamp for plants.
Common Light Compensation and Saturation Points for Plants:
| Plant | Light Compensation Point (umol/㎡/s) | Light Saturation Point (umol/㎡/s) |
|---|---|---|
| Grapes | 50.0 | 484 |
| Peaches | 2.7 | 484 |
| Tomatoes | 50.0 | 850 |
| Lettuce, Peppers | 21.0 | 311 |
| Strawberries | 43.0 | 320 |
| Oranges | 38.0 | 400 |
| Ginseng | 49.0 | 506 |
| Succulents | 49.0 | 749 |
| Cannabis (Veg) | 300 | 1300 |
| Cannabis (Flowering) | 650 | 1600 |
For cannabis during the vegetative stage, the recommended PPFD value is around 800 umol/㎡/s, with an 18-hour light period. For PPFD needed for flowering, it's about 1100 umol/㎡/s, with a 12-hour light period.
2. What is LUX?
LUX measures the brightness perceived by the human eye and represents the amount of light (lumens) received per square meter.
If LUX measures brightness, why can’t we use it to test the effectiveness of grow lights for plants?
The answer is simple: plants and human eyes favor different parts of the light spectrum. Our eyes are more sensitive to green light, while plants prefer red and blue light.
Red light helps promote plant growth and development, while blue light helps prevent excessive stem elongation and supports thicker leaves.
LUX can tell you if a room is bright enough, but it’s nearly useless for photosynthesis in plants.
LUX is primarily used to measure light brightness for humans, such as indoor lighting or streetlamp brightness. In contrast, PPFD is the key metric to determine if plants can thrive. If you want your plants to grow well, you need to focus on PPFD, not just how bright the light appears.
3. South African cannabis grow light
800w led grow lights
The 800W samsung full spectrum led grow light features a foldable design for compact size. It uses Samsung chips, providing high light efficiency with a PPF of up to 2080 umol/s and an efficacy of 2.6 umol/J. The coverage area is 2 to 3 square meters, suitable for a 150 * 150 * 200 cm grow tent.
Specification:
- Spectrum: Full Spectrum + 660nm Red Light
- Typical PPF: 2080 umol/s
- Efficacy: 2.6 μmol/J
- Dimensions: 113.4 cm x 100 cm x 8 cm
- Coverage Area: 2 ㎡ - 3 ㎡
1600W Full Spectrum Foldable LED Grow Light
The 1600W grow lamp for plants uses Samsung LED chips, offering high light efficiency with a PPF of up to 4640 umol/s and an efficacy of 2.9 umol/J. It has a dual-folding design, making the light 2.1 meters long, reducing the number of lights needed in a given area and lowering installation costs.
Specification:
- Spectrum: Full Spectrum White Light + 660nm Red Light
- Typical PPF: 4640 umol/s
- Efficacy: 2.9 umol/J
- Weight: 26 Kg
- Dimensions: 210 cm x 111 cm x 6.8 cm
- Coverage Area: 4 ㎡ - 5 ㎡
TheOneGrow is committed to providing high-quality cannabis LED grow lights. They have a warehouse in South Africa, offering free shipping, with delivery within 1-4 days, or self-pickup (contact us at: +27 63 153 5277).