Scope and starting point
PPF describes photons emitted each second; PPFD describes photons arriving per area each second. Coverage and uniformity therefore matter alongside source efficacy. For a constant measured PPFD of 500 µmol/(m²·s) for 16 hours, DLI is 28.8 mol/(m²·day). This is arithmetic, not a crop prescription.
Selection notes
Compare photon quantities with the same spectral interval and measurement plane. PPF is a source output; PPFD is measured at a surface. Map coverage, height, spectrum and uniformity. DLI depends on PPFD and time. Lux cannot be converted to plant photon flux with one universal factor.
Keep a reproducible record
Save the complete part number, source revision, operating point and the reason for each decision. Keep calculated examples separate from observed results. A measurement report needs its sample identifier, instrument and calibration details, stabilization, ambient conditions, raw record and uncertainty statement. Do not replace a missing value with zero or a typical value with a guaranteed limit.