Garden light meter (uses your phone's camera)
Most phones have a real ambient light sensor. This tool reads it and converts to plant-relevant categories (deep shade, dappled, part sun, full sun). Walk through your yard at different times of day to map exposure. Not a substitute for an actual lux meter on a science budget — but accurate enough to settle the "is this full sun?" question with a margin of about 15 percent.
Free · No signup · Works on phones with the Ambient Light Sensor APIClick "Start light meter". On most phones the browser will ask permission to use the ambient light sensor.
Lux ranges for outdoor plants
Per UMN Extension and standard horticulture references, midday outdoor light by category:
- Deep shade: under 1,000 lux — north side of buildings, dense canopy
- Part shade / dappled: 1,000–10,000 lux — under deciduous canopy
- Part sun: 10,000–25,000 lux — morning sun then shade, or filtered all day
- Full sun: 25,000–100,000+ lux — direct unobstructed sun at noon
For context, a sunlit windowsill at noon in summer is typically 10,000–40,000 lux. A north-facing room far from the window may be under 200 lux. Indoor lighting standards aim for ~500 lux for offices — which is far below part-shade outdoor light.