All the apps I compared to my meter was not correct. Way off matter of fact. Not saying every other phone app will be. But in my case
I'm not bitching about the $160 par meter like I was the apps. Going by the apps I would come back and notice stretching after a few days. Then you gotta correct it. The apps are off. You're either gonna burn them or they will keep stretching. A lot of waste of energy money and time in my case going through 3 harvest like that. Also being a new grower, I can say for someone that's new and learning with leds especially if it's a 600w
hlg, a par meter is somewhat necessary if you're solo and have no one with experience to personally be there and show you what's wrong. Just my 2 cents from my last year of learning