You can buy real meters to do real measuring and math, not interpolation and modelling (which is what photone does). Bonus is that real meters often come partitioned by wavelength, which can be even more illustrative for us growers. Not hating on it, if you don't have any idea then yes use it. Pretty much any serious/valid review of it I have seen boils down to 'this I use for anchoring only' as in, they use it to get a number then using the same settings see what their changes do to the readings