Try the Playstore and search ppfd, I use it and it does work well, I cross checked the app on three different phones and got the same reading. I'm sure it is not accurate like the $$$ Apogee and it maxes out at 965 ppfd. For the price it is a lot better than just a generic manufacturer recommendation graph. It also has the DLI feature which is nice. Maybe Mr. Grow It can cross check its accuracy against his high dollar one....
Try the Playstore and search ppfd, I use it and it does work well, I cross checked the app on three different phones and got the same reading. I'm sure it is not accurate like the $$$ Apogee and it maxes out at 965 ppfd. For the price it is a lot better than just a generic manufacturer recommendation graph. It also has the DLI feature which is nice. Maybe Mr. Grow It can cross check its accuracy against his high dollar one....