What is P.A.R?
Plants and people have a completely different view of light. People mainly look in the middle of the spectrum. You’ve probably heard of the term lumen, which is a term based on the model of the human eye and how strong the light is displayed to the human eye. The arc shows that people are much more sensitive to green light than blue or red. Plants look at this in a completely different way. Plants are more sensitive to blue and red light to stimulate photosynthesis. P.A.R. stands for photosynthetic active radiation and can be found from blue (400nm) to red (700nm). PAR actually shows what kind of light is needed to realize photosynthesis. The amount and spectral light quality of the PAR light is important to consider for your lighting solution.
How do I measure P.A.R?
P.A.R. covers the range of 400-700nm. The unit of measurement within P.A.R. is photons expressed in micromol per second (μMol/s). Measuring the number of photons within P.A.R. is possible with a quantum sensor and, in combination with a light meter, can measure the direct light intensity on the crop. It is also possible to measure the cumulative light intensity with a data logger. That way you have a report of the whole day. We call this DLI.