So I had some led bulbs with no specs. and wanted to see if they might be any good in the grow room but not having a light meter I had to find an app that could measure the Kelvin temperature,,,, So far pretty useful and it came within 4% when reading lights I had spec sheets for Photone - Grow Light Meter
I'd say less than stellar but close enough for how I'm using it based on reddit responses from others. Works better with some phones than others too it seems according to the writers.