Practical light checks at home
Compare window and shelf light before moving a houseplant
Compare two real plant positions with the same phone and timing, keep a simple log, and avoid choosing a spot from one bright midday reading.
LumaLeaf guide · Reviewed
Start with a fair comparison
Choose two actual leaf positions and measure them close together in time with the same phone and sensor orientation. Repeat at different times. A window label or the brightest single reading does not describe everything a plant experiences.
University of Minnesota Extension recommends checking both the quality and hours of natural light before choosing plants. Its examples describe window exposure, while also showing that roof overhangs can interrupt direct light. Use your own measurements to inspect the actual position.
1. Name two positions you can reproduce
Call the current position A and the candidate B. Describe the shelf level, approximate distance from the window and leaf height. “Living room” is too broad to reproduce. “Shelf A, upper leaves, behind the open curtain” is more useful. Keep both candidates practical: a bright place may still block a walkway or put leaves against a hot window.
Leave curtains, blinds and lamps in their usual state. Use one phone throughout the comparison. Different devices may respond differently, so mixing phones adds another variable.
2. Measure A, then B, then A again
- At A, hold the sensor at the chosen leaf height and record lux or its observed range.
- Move to B and repeat with the same orientation as soon as practical.
- Return to A. If its reading changed markedly because clouds moved, label that round as unstable and compare again later.
- Repeat in the morning, around midday and later afternoon. Add another day when conditions differ.
The return to A is a simple consistency check, not a calibration. Record sunlight patches separately from steady indirect light rather than treating a brief peak as an all-day condition.
Use a short log instead of memory
| Time / conditions | A: current shelf | B: window stand | Note |
|---|---|---|---|
| 09:00, overcast | 450 lux | 900 lux | A stable on return |
| 13:00, clouds moving | 600–1,400 lux | 1,100–3,200 lux | Repeat round |
| 16:00, clear | 300 lux | 700 lux | No direct patch |
In this invented example, B is brighter in the stable comparisons. That does not prove it is right for every species. Check the plant’s needs and how long each condition lasts. Do not average three snapshots and call that DLI.
3. Make one change and keep observing
If you choose B, save a new baseline there and keep the other care conditions as consistent as practical. Watch the plant over the following weeks, taking note of new growth and damage. Recheck when seasons, curtains or neighboring plants change.
LumaLeaf lets you name both spots and save readings so you can compare them again. If readings are close or fluctuate more than the difference between spots, collect more observations before declaring a winner.
Continue with another guide
- How to measure plant light at leaf height with your phone
A repeatable lux-check routine: find the sensor, measure where leaves sit, record the conditions and compare readings without treating one number as a diagnosis.
- Lux vs PPFD: what a phone light sensor can and cannot tell you
Understand lux, PPFD and DLI before comparing grow lights. Learn why a single conversion factor or phone reading cannot provide a calibrated plant-light assessment.