I see there is some debate about the validity of the readings, these are the numbers I got -
44" above phone, Medic Smart Grow light, set to 40% ( 300 watts) DLI - 16.8 & PPFD - 195
Do these seem reasonable, as in ballpark ? I just want to use them as a guideline, I'm going to trust my eyes and what little common sense I've got left.
Just finished my first grow with this new light and I'm sure that I overdosed the plants with too much light. It was by far not my best effort .
I can't advise on the specific readings you are getting.
Photone readings are close enough if calibrated to your specific light, but debatable otherwise. I believe that the problem is that the sensor in the phone does not have the same sensitivity to different wavelengths of light that a proper par sensor does, so it may not detect all the wavelengths that are important for plants, or accurately determine wavelength distribution. When you get a reading off the photone app, you are getting a light intensity reading which, while not measuring par properly, can be used to calculate likely par levels
if the app has been calibrated for your specific light. Absent specific calibration, the app has no way of knowing what your specific light is producing that cannot be measured by the phone sensor. Bottom line is that good calibration will mean decent predictions, poor or absent calibration
may make poor predictions, and you will have no way of knowing how close they are.
One additional complexity is that if you compare with published PPFD maps, you have to do so in the same enclosure used when making the PPFD map. The size of space being illuminated, and the reflectivity of the walls makes a big difference to ppfd distribtion. And you can't get an appropriate reading with the tent door wide open, you have to take the reading with the enclosure as close to sealed up as you can manage. If I take a reading with my par meter with the drobe door open, the readings are quite a bit lower than with the door nearly closed.
If you have access to a par meter, you could calibrate your phone well yourself, but careful use of PPFD maps should get you close enough.
All just my two cents worth, good luck with it. Fine looking light by the way.
