A must have for every photographer. If you are a pro you know what you are doing but if you are not yet there then this digital light meter will be extremely helpful. You just connect / attach it to your smartphone and you are all set to go. Use free app to measure luminance, it will show you all kinds of parameters, which you then simply insert in your camera and you will then take the most awesome photos Sure, smartphones also have sensors but they are nowhere near this. Like makers say: There is no darkness too dark and no light too bright which Lumu can’t measure.