If you are comparing the measurements from your Lumu Power to some other light meter please check first:
- how high is the offset (expressed in EV steps)?
- is the offset constant through all illuminance levels?
If the offset is small (<1.0EV) and constant through the whole range, this is normal. Each manufacturer uses slightly different EV calculating algorithms and constants. Even the photographic ISO 2720-1974 standard doesn't specify any exact numbers, only suggests ones. That being said, light meters from Sekonic, Lumulabs, Gossen and Kenko/Minolta will always give different readings.
We made our calculations the way the ISO standard suggests it.
Light meter is your own tool and you have to tune it to your shooting taste and needs. You can do that by going to general app settings (gear icon in top left corner on the first screen) --> General Settings --> Lumu Power calibration --> EV calibration.
If the offset isn't small and constant, write to us at firstname.lastname@example.org. Tell us:
- which Serial Number does your Lumu Power have
- what type of lights are giving you problems
You might have received a faulty unit, which doesn't happen often, or maybe there is a problem with measuring specific light types. The latter needs to be solved with the Firmware or iOS app upgrade, and we can be more effective with your help.