The PAR window
PAR usually refers to photons between 400 and 700 nm. It gives lighting teams a shared baseline for evaluating plant-useful energy.
PAR and spectrum differ
Two sources can produce the same total PAR with different spectral shapes. Blue, green, red, and far-red balance can change crop response.
From fixture data to crop data
Fixture specifications are measured under controlled conditions. Field measurement accounts for distance, reflection, dimming, age, and canopy geometry.
Practical next step
A robust PAR workflow combines repeated measurements, consistent placement, and spectral capture to support purchasing and production decisions.