Intensity of a light is measured over a fix area to understand the ability of a light to cover an area with that intensity (coverage).
Micromoles of photons per square meter per second (µmol/m2/s) measures the intensity and by taking measurements in a consistent 4 x 4 grid, measures the coverage of that intensity–commonly known as PPFD per 4 x 4 grid.
Rather than measuring light intensity by lumens per watt with a lux meter, growers should use a quantum PAR meter to measure the micromoles of photons per square meter per second (µmol/m2/s) at the canopy level.
To best calculate PAR light intensity coverage using PAR mapping 4 x 4 grids be sure and measure at various heights. Spot readings (PPF) metrics are misleading.
Smartgrow Systems recommends growers use PPFD per square meter to accurately measure intensity and coverage of that intensity.
In addition to PAR light intensity, plants need a tailored spectrum designed to maximize photosynthesis. Cultivated plants require high intensity and broad but balanced spectrum. Two grow cycles (veg/cloning and flowering/bloom) require different spectra to maximize results.
It’s important to use a light that concentrates energy on the blue and red part of the spectrum, for growth and flowering respectively.
However, smaller amounts of yellow and green wavelengths are also needed for optimal growth. In the end its all about intensity, micromole levels at the canopy and providing plants the proper spectrum for target plant species. New spectrum combinations are sure to be on the horizon as growers experiment more.
DAILY LIGHT INTEGRAL (DLI)
DLI is defined as the amount of photosynthetically active radiation (PAR) delivered over a 24-hour period. It is measured as the number of moles (particles of light) per day (mol.m-2.d-1 ), and often abbreviated to “moles/day” (or m/d) in trade journals.
DLI is the total quantity of micromoles of photons per square meter per second delivered over the course of an entire day. Plants have an optimal DLI for various growth and flowering stages which drive light recipes (intensity and spectrum) and lighting duration plans.
Click http://smartgrowsystems.com/plant-light/ for details..