If you want to know how grow lights compare, you've probably come across the measures PPF and PPFD.
However, you may be unsure of what these indicators indicate and how to interpret them in order to make an educated purchase choice. In this essay, we will look at the key distinctions between PPF and PPFD.
The distinction between PPF and PPFD by definition
PPF and PPFD are two acronyms that deal with the quantity of light for a light source or place.
PPF - Photosynthetic Photon Flux
PPFD - photosynthetic photon flux density
What precisely constitutes a photosynthetic photon?
A photon is a single particle of light that may have different wavelengths. Those that can contribute to photosynthesis are known as photosynthetic photons.
This comprises photons with wavelengths ranging from 400 to 700 nm.
PPF and PPFD measure the number of such photons. The important distinction is that PPFD measures the density of photons falling on a specific surface, while PPF measures the overall number of photons produced by a light source.
In the graph below, each dot represents a single photosynthetic photon. PPFD is the number of photons that settle on a certain surface, while PPF is the total number of photons emitted by the light source.
First, the PPFD value increases as you go closer to the light source. This is because light disperses as one goes away from its source.
Second, the center of the beam usually has the greatest PPFD measurement. As you travel away from the center, PPFD decreases.
PPF and PPFD units of measurement
PPF - μmol/s.
PPFD - μmol/s/m2.
Both PPF and PPFD count the total amount of photons. This is a huge amount, hence the unit micromoles (μmol) per second is used. A micromole is comparable to around 6 x 1017. Furthermore, since we are monitoring the rate of photons, we count them per second.
PPF is just micromoles per second, while PPFD is micromoles per second per metre squared. This is because we want to know how many photosynthetic photons fall on a square metre each second.
When should you utilise PPFD or PPF?
PPFD should always include a distance and location. Most manufacturers will offer PPFD statistics, however be careful to take into consideration:
Distance from the light source.
Location and if this is averaged across a certain region.
Without this information, you cannot effectively compare PPFD.
PPFD may be caused by several lights illuminating the same area.
In contrast, PPF measures the amount of PAR produced by a single grow lamp. You may make significant comparisons between lights by comparing their PPF measurements. However, depending on the product, the resulting PPFD values may be affected by the beam angle.
Measurement technique discrepancies between PPFD and PPF
Because PPFD is a measure of how much light falls on a surface, even a tiny, portable light meter or spectrometer can detect the quantity of PAR falling on a surface. These are often less expensive and may be linked to cellphones for usage in the field.
PPF, on the other hand, quantifies the quantity of PAR emitted from a single light source in all directions. Thus, significantly more advanced instruments are necessary. Typically, a goniosphere or integrating sphere is required. These gadgets catch and measure the light emitted from all angles.
