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 Partial Absorber

Cover your phone’s light sensor with a piece of paper (any type of paper works in this specific case). This will absorb some of the light.

Step 2: Disable Diffuser Detection

If you've granted camera permission, Photone will detect the piece of paper (which also acts as a diffuser) and show this warning:

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

Step 3: Calibrate

Because the some of the light is now blocked, you must apply a custom calibration to counteract the loss in light transmission:

1. Remove the paper.
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 paper 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.