The PAR your grow light puts out is much greater than the PAR that reaches a canopy 18” away. Measured in “micromoles per second” and expressed as: μmoles/second. 2 /s) Common mistake in literature: plants were grown at 200 µmol/m. PAR is often confused as a type of measurement, but is more the designation of a region of light within the spectrum that is usable to plants. 2 /s of PAR As we explain below, there is a limit to the density of photons that plants can use. Research grade measurement of photosynthetically active radiation (PAR), ePAR, PPF, and PPFD. Apogee Instruments Quantum sensors are a trusted standard for measuring photosynthetically active radiation by agricultural professionals all over the world. This article covers the PPFD (PAR) targets I aim for with my orchids and houseplants (on a 12h daily cycle); please understand these are my personal estimations and guidelines—they’re not coming from a book or study. Light quality declines as you move farther away from the light source. Photosynthetic Photon Flux Density (PPFD) A measurement of the light (photons) that reach the target each second. ... See our PPF to Lumens calculator here Need to convert lux to PPFD micromoles per second per meter squared? PAR vs PPFD • PAR is photosynthetically active radiation (400-700 nm) • PPFD is photosynthetic photon flux density (µmol/m. the amount of light delivered to your canopy) every second. This is the number of photons in the 400 to 700 nm waveband incident per unit time on a unit surface. PPFD stands for Photosynthetic Photon Flux Density, and is the same as PPF, but takes surface area into account as well. PPFD (Photosynthetic Photon Flux Density) measures the amount of photons within the PAR region at a specific location (e.g. Photosynthetic Photon Flux Density (PPFD) PPFD measures the light photons that are emitted over one square meter per second and is expressed in µmol/m 2 /s (micromoles per square meter per second). See our lux to PPFD calculator here. PPFD (photosynthetic photon flux density) tells you how much usable per second actually reaches your plants. The maximum density of photons (PPFD) ultimately determines the maximum quantity of photons (PPF) that we can provide in a grow space. This is typically the number that is shown to you on a handheld PAR meter. PPF tells us how much PAR is emitted by a light source. You may find yourself comparing LED grow light specifications, where one light uses lumens and the other uses PAR units such as PPF (umol/s). Photosynthetic Photon Flux Density (PPFD) describes the density of PAR photons at some specific spot (the place it is measured). The preferred measurement for PAR is Photosynthetic Photon Flux Density (PPFD). Other Posts. PPDF- (Photosynthetic Photon Flux Density) is a measurement that is very important to your plants. If you have a PAR meter, it is reporting PPFD (μmol/m2/s) measurements. PPFD is measured in micromoles per meter squared, per second (µMol/m 2 /S).