Very early in his houseplant journey, Darryl Cheng realized the term ‘bright indirect light’ is often used as a catch-all phrase that doesn't provide any concrete way of assessing the light your plant is receiving. 

Here is the LTH Meter – the first meter to measure light, temperature, and humidity.

Key Features:

1 – Convex Mirror
Correlate your visual surroundings with the light measurements

2 – Light Sensor
Measures light in FC (foot-candles) or lux

3 – Temperature/Humidity Sensors
Measures temperature in °C or °F and humidity in %

4 – Display
Shows measurements for light, temperature and humidity in real-time (refreshed every 0.5 seconds)

5 – Wrist Strap
Sturdy, custom woven wrist strap

Requires 3 x AAA batteries (not included).

How to measure natural light:

• Sensor placement: top of the plant
• Sensor orientation: should be pointed straight up but if you find that you have to turn the sensor to get a higher reading, it just means over time, the plant will tilt towards that direction
• WHEN to measure: the purpose of the light meter is to measure the strength of INDIRECT light so you want to get a sense of the average strength of this light while the sun is NOT in view (and also not too close to sun rise or sun set – when the overall sky is darker)
• DIRECT SUN: also take note of the total duration the sun shines directly on the plant

Analysis for natural light:

• If the average indirect light is above “Good for Growth”, then expect good growth
• If the average indirect light is at or below “Minimum for Maintenance”, then don’t expect strong growth
• If the duration of direct sun is above the “Tolerance of Direct Sun”, then block it with a white sheer curtain
• If the duration of direct sun is at or below the “Tolerance of Direct Sun”, then there’s no need to block the plant (just be sure to keep up with watering)

For white LED grow lights:

• For good growth: set the distance of the grow light such that the reading at the top of the plant is at or above “Good for Growth” and keep the light on for 12-16 hours a day
• For maintaining over winter: set the distance of the grow light to get a reading around the “Minimum for Maintenance” and keep the light on for 8-12 hours a day