I'm using an Iphone. Now I’m having my doubts on its accuracy.
That's wise (says the 67 year old skeptic who's been a skeptic most of his life).
I have no reason to doubt the info that growlightmeter.com ("GLM") puts out about accuracy when they specify a given device. In the emails between their programmer and me, he came across as nothing but forthright so if your phone is one of the models for which they have test results, you should be good to go. On the other hand, lacking that, the only way to know if you're in the ballpark is to compare it to another source.
AC Infinity - love their products but some of their lights aren't for me. I use four or five lights over the course of a grow and I bought them because they have specific characteristics. The spectrum of the light (the different wavelengths that comprise a the spectrum of the light) and the PPFD map (a visual representation of the light output) are the two big factors. Their spectrum is OK - it's heavy in the blue which means you'll have short, compact plants with lots of foliage) but there's a price to pay for that because blue photons reduce yield.
That's a lot of blue but and a hump in orange and "light red" vs the more standard hump in the deep red, at 660nm.
The bigger issue is that, like all board lights, it has a hot spot in the middle.
Cannabis thrives under lots of light. The "light saturation point" for cannabis, in ambient CO2, is 800-1000µmol. Above that amount of light, cannabis can't process the incoming photons so leaf damage will eventually occur. To get a grow to run at 1000µmol, you've got to have every thing other than light optimized (that's the parameters of growth that I posted before). With that in mind, check out the PPFD map for the S44 at, say, 14". Somewhere under dead center, the light is putting out 1500µmol. That's useless unless you're running CO2. In the 2' square around the center, the PPFD is 1250±µmol. Again, unless you're running CO2, you can't use that much light. The highest I've ever run a plant was just over 1000µmol so let's say that your grow can handle 1000µmol. To get the center down to 1000µmol, you've got to reduce the dimmer by about 20%. When you do that, the PPFD everywhere in the tent will drop by 20%. That's great in the center but not so great if your plants are in the 1' strip around the edge. At 100%, that's 700µmol but when you drop the dimmer setting, that 700 become 700*0.8 which is only 560.
If you check out the Bugbee or DeBacco videos, you'll see that 600µmol is the minimum recommended PPFD in flower (DeBacco mainly repackages Bugbee's stuff in his videos about light, BTW) but, if you're dropping the dimmer setting to get to 1000 in the middle, you're only at 560. That's not a feature but it's not a bad bug.
Consider two issues - many grows won't handle handle 1kµmol and AC Infinity is…blurring the acutal values in their PPFD map.
First issue - it will take a few grows to get things set up so you can hit 1k. Sure, it's not hard to get a crop but it takes a while to get everything dress right dress so that you can get a grow right at the top end of what the plant can absorb. There's some knowledge and planning involved but, unless you're using clones in a controlled grow environment, there's some luck involved, too. All in all, if you can run 800 or 900 when you start out, you're doing well.
Second - AC Infinity is reporting PPFD using 1' squares. That's a fudge. Industry standard is 6" and with more detail, we would see that those 700±µmols blocks may be 800 on the inside but only 500 at the edge. Those are guesstimates on my part but they illustrate the problem - if your outside 1' of your grow area is averaging 560 µmol, that really reduces the area that you can use to grow.
OK, the above is pretty down in the weeds but it's also completely true. It's not a knock on AC Infinity but it's primarily a function of how board lights work and that's a reason why the industry has moved away from board lights in favor of bar lights.
What's the good thing about board lights? They tend to be cheaper than bar lights. The R&D cost is very low and product cost is low, too, because they're easy to produce, package, and ship.
I would go with a different light but you might be ready to burn me in effigy (I haven't delivered any good news, I realize) and you may not be able to, or want to, return the light.
If you keep the light, just be aware of the light fall off once you leave 2' square area under the light - meaning a square 2' x 2' under the light. You'll still have light at, say, 3' from the center but there's a lot of fall off…and that's where it's really helpful to have a light meter.
Also, you can (sorta) calibrate your Photone setup using your light as a "known good" source. The idea is that at 18" hang height, the PPFD level 1' from center mass is about 1100µmol so you could slide your phone to a spot about 1' from center mass of the light and calibrate Photone against that. I wouldn't say that it's accurate but it's less accurate than not calibrating it. Again, for my money, I'd go with the Uni-T. I appreciate having an Apogee but, in terms of value, the Uni-T is a bargain and it's,
in practical terms, as accurate as an Apogee.
If you're willing to swap lights and want to stay at that price point, I'd go with two Vipar Spectra XS-2500 Pros. Each 2500 consists of 2 XS-1500 Pros that are held together and the XS 1500 Pro, a board light, is an absolute stunner. It has a better spectrum and a better PPFD map than the Ionboard and, since it's two sets of lights, it's much easier to deal with plants that are at different heights.
Per the PPFD map, the values in the center of the PPFD map are not as high as those in the Ionboard but check out how even the numbers are all the way to the edge. At 11", the PPFD values only go up to 900 but they're at 800 at the very edge of the tent. That uniformity is better than my $600 Growcraft light. Check out the 16" numbers - yes, they're lower, as expected, but even at 16" almost the entire canopy will be > 600µmol.
