PlantUse light readings to compare places and times. A single lux measurement cannot describe a plant’s entire day.
Measure where the plant actually grows
Hold the meter or phone at the level of the leaves and follow the device’s instructions for sensor direction. Avoid shading the sensor with your hand or body. Measure in the same orientation when comparing two shelves or window positions.
A reading beside the glass is not a reading at the back of a bookcase. Small changes in position can have large effects. Write down distance from the window and any curtains or nearby foliage so the comparison can be repeated.
Build a daily picture
Take measurements at several times on more than one day. A short sunny interval can produce a high number while the rest of the day stays dim. Cloud cover and seasonal day length also change the total light available.
A practical first exercise is to compare three candidate locations at similar times. This tells you which is brighter without pretending to know an exact light prescription for every species. Combine those observations with the plant’s growth and established care needs.
Understand lux and sensor limitations
Lux weights light according to human visual sensitivity. Plant lighting is often discussed using photosynthetic photon measurements instead. Converting lux to a plant-specific photon value depends on the light spectrum, so one universal conversion factor is misleading.
Phone hardware and measurement methods vary. A built-in sensor or camera-based estimate can provide useful relative guidance, but it is not automatically a calibrated horticultural instrument. PlantPal’s light meter is best paired with consistent technique and an understanding of those limits.
Use results to make gradual changes
If a location is consistently much darker than another, consider moving a light-hungry plant closer to the brighter area. Acclimate it gradually if direct sun exposure increases. Watch new leaves, spacing between leaves, and signs of bleaching or scorch.
Revisit measurements when seasons change or a plant grows into the light of another. Save the plant’s zone and observations in PlantPal. The number is useful because it supports a better care decision, not because it replaces observation.