I just compared my phone (Pixel 3a) to my Uceri meter, using the app that you link to here.
It seems okayish. The main issue with it is that the camera has a limited field of view, so it does not capture light coming from every direction. With the lux meter and the phone both pointed directly at the lamp near my desk, the phone reads about 35% higher than the lux meter, and when they’re both pointed at an angle that barely excludes the lamp from the field of view, the phone reads 45% lower than the lux meter. The reading on the lux meter only changed by 4% between these two angles.
I’d say if you’re okay with getting within a factor of two, the phone app is fine. The phone and the lux meter seem to agree the best when the lamp is just barely inside the field of view of the camera.
I have compared a professional luxmeter with the free app “GPS Status” which also displays a Lux value. The readings were within 30% tolerance for normal lighting situations. A smartphones light sensor will clip at some (high) value though. This clipping value can easilly be tested by pointing the sensor directly towards the sun.
It might well depend on the smartphone model. My tests were done with an older Motorola and a Oneplus 6. I’d guess a free app will be sufficient for most purposes.
Another thing that might be worth considering is that if you want to estimate your body’s response to light, a camera-based illuminance meter with a very wide field of view and some amount of clipping is probably better than a standard lux meter with a diffuser, since it will account for whether the light is spread over your full field of view or not.
Is there much benefit in getting the Uceri meter rather than using a free phone app like Light Meter which uses my phone’s camera to measure the lux?
I just compared my phone (Pixel 3a) to my Uceri meter, using the app that you link to here.
It seems okayish. The main issue with it is that the camera has a limited field of view, so it does not capture light coming from every direction. With the lux meter and the phone both pointed directly at the lamp near my desk, the phone reads about 35% higher than the lux meter, and when they’re both pointed at an angle that barely excludes the lamp from the field of view, the phone reads 45% lower than the lux meter. The reading on the lux meter only changed by 4% between these two angles.
I’d say if you’re okay with getting within a factor of two, the phone app is fine. The phone and the lux meter seem to agree the best when the lamp is just barely inside the field of view of the camera.
I have compared a professional luxmeter with the free app “GPS Status” which also displays a Lux value. The readings were within 30% tolerance for normal lighting situations. A smartphones light sensor will clip at some (high) value though. This clipping value can easilly be tested by pointing the sensor directly towards the sun.
It might well depend on the smartphone model. My tests were done with an older Motorola and a Oneplus 6. I’d guess a free app will be sufficient for most purposes.
Another thing that might be worth considering is that if you want to estimate your body’s response to light, a camera-based illuminance meter with a very wide field of view and some amount of clipping is probably better than a standard lux meter with a diffuser, since it will account for whether the light is spread over your full field of view or not.