Here's an article looking at light intensity in the vegetative growth stage:
Although the vegetative stage of indoor cannabis production can be relatively short in duration, there is a high energy demand due to higher light intensities (LI) than the clonal propagation stage and longer photoperiods than the flowering stage (i.e., 16 – 24 hours vs. 12 hours). While...
www.preprints.org
High light intensities can be used to grow healthy and robust cannabis plants during the vegetative stage of indoor production
"... the objective of this study was to determine the effects of a broad range of LI (light intensities) on vegetative stage cannabis morphology and growth attributes ..."
"Since the number of nodes saturated at relatively low LI, a canopy-level PPFD target of about 900 μmol·m-2·s-1
may be most appropriate for producing robust but not overly compact plants while also minimizing
lighting-related energy and infrastructure costs. Although not as common in commercial settings, production
facilities that target more open plant architecture and greater energy conservation may opt for canopy-level PPFD target of ≈ 600 μmol·m-2·s-1."
From the abstract: "Generally, PPFD levels of ≈ 900 μmol·m-2·s-1 produced compact, robust
plants that are commercially relevant, while PPFD levels of ≈ 600 μmol·m-2·s-1 promoted plant
morphology with more open architecture – to increase airflow and reduce the potential for
foliar pests in compact (i.e., indica-dominant) genotypes."