Beyond watts: what should a lighting brief measure?
Separate electrical power from the light reaching the organism or illuminated area.
Start with the measurement plane
Wattage is electrical power. For a useful comparison, specify where light should be evaluated: a coral position, the plant canopy or another working plane. Mounting height, beam distribution and geometry affect the result.
Plants: intensity and time work together
Photosynthetic photon flux density (PPFD) describes the rate of photosynthetically active photons reaching an area. Daily light integral (DLI) describes the total received over a day. Purdue explains that daylight and supplemental lighting both contribute; the appropriate target depends on the crop and stage.
Aquatic systems need context
For an aquarium, include water depth, organism position and the intended lighting schedule. Do not transfer a plant-lighting target directly to corals or infer biological performance from wattage or a colour photograph.
What to send with an enquiry
Share the layout, dimensions, target measurement plane, any existing readings and the intended schedule. Ask for information relevant to the selected model and the actual installation conditions.