How To Fix a Peaking Ambient Light Sensor (ALS)

A workaround to fix an ambient light sensor (ALS) reaching its limit

Is your reading stuck even though the light keeps getting brighter? That means your devices’s built-in ambient light sensor (ALS) reached its limits. This is not an app error but a physical limitation of the sensor built into your specific device.

If you don't want to upgrade your smartphone to one that supports enhanced light intensity measurements using the camera you can apply this simple workaround:

Step 1: Add a Diffuser

Cover your phone’s light sensor with a simple diffuser to block excess light. The easiest DIY version: tape a small strip of printer paper over the sensor (any type of paper works in this specific case).

Watch this video to see how to build one:

Step 2: Disable Diffuser Detection

Photone normally warns you not to use a diffuser with the ALS:

Since you’re doing this intentionally, you can remove the warning by disabling the automatic diffuser detection under Settings (⚙️) → Danger Zone → Diffuser Detection.

Step 3: Calibrate

Because the diffuser blocks some light, you must apply a custom calibration to counteract the loss in light transmission:

1. Remove the previously built diffuser.
2. Create stable lighting where your sensor doesn’t max out.
3. Let the lamp warm up until its output stabilizes and the measurement values no longer change over time (this may take a few minutes)
4. Take a reference measurement and write it down as.
5. Reapply the diffuser and place your device at the exact same spot
6. Perform a calibration using the setting "Light- / PAR-Meter" and input your previous measurement where it says "Your Meter's Reading". You may also use the video below as a guide.

✅ Done! You can now measure higher PPFD, DLI, and lux levels without clipping.

Still Having Issues?

If your sensor still maxes out, reach out to our support team — we’ll help you troubleshoot.