How to use your watch as a light meter with no phone app

Why the usual way fails

Phone light meter apps read the sensor near the front camera, so you end up holding the phone face up at odd angles while the number jumps with every move of your hand. Some free ones come with ads or ask you to sign in, which is a lot of overhead for a number you check now and then. Watch apps that lean on a phone companion stop being useful as soon as the phone is in another room. And a proper handheld meter gives better numbers but costs more than a casual check is worth.

How WristLux helps

WristLux runs on the Wear OS watch by itself, with no account and no phone companion. It reads the watch's ambient light sensor and shows live lux or foot-candles, with modes for general, desk, reading, plant, photo, outdoor and evening checks. You can hold a reading while the meter keeps running, and each session keeps its minimum, maximum, average and duration. It costs 0.99 USD on Google Play and is meant as a quick reference rather than a certified meter.

Step by step

1. Install WristLux on your Wear OS watch from Google Play; there is nothing to set up on the phone.
2. Open it and pick the mode closest to what you are checking, such as desk or reading.
3. Push your sleeve back and hold your wrist still, with the watch face pointing the same way each time.
4. Hold the reading once the number settles, and leave the meter running if you want to compare.
5. Check the session's minimum, maximum and average before you move on to the next spot.

Tips

• Take every reading the same way. Wrist angle, shadows, sleeves and cases all change what the sensor sees, so a reading is only comparable with another one taken in the same pose.
• Compare places rather than chasing an exact figure. Two readings from the same watch tell you which spot is brighter much more reliably than one number tells you the true lux. If the desk reads about half of what the window does, that is useful to know even if both numbers are a little off.
• Use the basic calibration if you have something to compare against. If a friend's meter or a known light gives you a reference number, you can nudge WristLux toward it.
• Switch to foot-candles if your lighting guide uses them. Many US lighting recommendations are written in foot-candles, and reading the same unit saves you converting in your head.

Questions