I’ve been doing something similar but one minor argument against it is the consequences of the inverse cube law. That would kick in with plants or canopies at different heights.
Cheers
G
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It’s all give n take . Can’t have it perfect all the time , so I error to the lower height and power levels .
What I’m trying to say is this
If you place you light 4 feet above the canopy at 100 percent and read par at tallest plant in middle . Then read at tent floor
Now lower light to 15 inches set power level to same par as above at middle at top plant. Maybe 40 to 60 Percent power . Read level at floor
It’s the SAME ! Law says it has to be .
So run at 36 inches and 100 % power if ya want , your money
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You are absolutely right about using a light meter, I can’t function without one now…It takes so much guesswork out of the equation.
Another observation on lights; large, spread-out lights have a more even distribution pattern. The corners are still lower but not as bad.
One downside is they are harder to raise and lower but I still manage… 
I was thinking about a SCROG setup the other day and wondering just how close I could get the light to the buds (using the light meter)…
Cheers
G
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I have an apogee full spec quantum meter but hardly use it. Probably should to gauge deterioration of my lights over time at least. In a scrog setup or where a very uniform canopy is in play i could definitely see the use and appeal though.
I remember in the past during the blurple era that quantum/par meters were mostly useless unless using a thousand dollar Li-cor because the sensors used didn’t give accurate readings with red light (660nm) (which was the majority of diodes used in blurples).
Now that 660s are re-emerging in the white-spectrum lights I thought maybe it would be worth pointing out that not all quantum meters provide accurate readings still to this day.
Example of the spectral range in the original apogee sensors.
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I’m late to the party, but you can falsify the fiber thesis by using a hollow stem to make fiber. I would venture to say the length of the fiber is important when choosing a fiber cultivar. Like not many branches and really tall. The fiber for making materials like cloth is located in the green layer you strip off the outside of the plant aka the bast fiber. The hurd fibers contain natural polymers for the manufacture of plant based “plastic”.
make fiber: strip the green bark off the cannabis stalk after harvesting the buds. boil that for a half hour in 1/2 cup washing soda and water in a pot. Card the fiber. Make batt. It’s a lost art.
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@JoeCrowe What the heck does your post have to do with the current discussion??? 
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Do those apps actually work well? How’s the accuracy?
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hah hah yah it was a post from 20 days ago about what kind of plant produces good fiber.
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Everyone says yes but not many people mention that every phone has a different sensor in it. iPhone has so many models. So when someone says iPhone you don’t know if they are using it on an iphone4 or an iPhone14pro max. I would say the newer the phone, more likely it’ll be more accurate. But even still. Top of the line Iphone 14 and bottom of the line iphone14 would have different cameras
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Yeah that’s my knowledge of it as well. No way they’re calibrated against every camera.
@jetdro what iphone do you have? And are you using a paper diffuser? And is it on the ‘Full Spectrum LED’ setting?
With that setting on, with this iphone8, photone is telling me I require a paper diffuser which I did. But I’m getting at least 100+ less ppfd than you are at the same height and settings 
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Yeah I agree. I just read an article comparing various apps on Android phones and they found the results to be “wildly inaccurate.” I probably wouldn’t waste my time.
I was checking out this one called the SpotOn Par Meter.
…and also the Phantom PhotoBio Par Meter that I’ve seen for under $200.
I’d have to research more before I pulled the trigger.
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I wouldn’t even bother on the android side. There’s too many phone’s to do it at all there. You’d need to be on the same phone as the developer. The iPhone’s though could all be pretty similar. Least within certain year ranges I bet. Should have a closer chance at being accurate. Honestly the accuracy doesn’t matter too much either though obviously the closer the better. But as long as you keep using the same thing every time, you can go off that and how the plants look to dial in where it should be. Still not going to have a clue what exact par/ppfd you’re at 
but you’d have numbers to use for references to dial things in.
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And that makes the $6 a worthwhile investment for tracking sake, but not for scientific data
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13 Pro Max . You must use 22lb paper diffuser
What is your tent size? I told you there was a 100 par level difference in my tents
Had i done it in my 5 x 10 it would be lower than what i gave you
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Ah ok cool. probably the difference then. I’m unsure on paper weight and tent is a 4x4 but technically it’s 4.5ft square.
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To me that’s the only side. lol
I’m a Samsung Galaxy Flagship Phone user. It’s generally the most powerful phone spec wise, has the best quality OLED screen… and largest camera sensor at release… I’ll buy a Par meter because of accuracy and strive to have everything dialed in on my grow in every aspect… but that’s the OCD speaking. I always obsess over the little things. When I buy some of these new light bar type LEDs like the Spyderfarmer SE7000… the way I see it a couple hundred to three hundred bucks isn’t bad considering the price of the lights themselves. I can’t wait to move and design a new room. It’s what I’m saving for right now. I used COB type leds before and didn’t care much for them… these new lights really amaze me.
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Alright, day 3 of flower.
SSDD F2 #1 girl still pissed the F off at the uppot. I’m positive she’ll pull out of it though. If anything, this is hindering her stretch which I’m kind of fine with. Light is at 60% and right around 15-18 inches above the canopy. iPhone8 says ~550-600 ppfd at the canopy and like 250-300 at the top of the pots. See what happens. Only other news was I had a PH spike in here yesterday for 1-2 waterings that I didn’t catch. Forgot to dose the calcium hypochlorite
so I got that in there last night and adjusted the ph back down to 5.85-5.9 ish. Other than that, I have crushed the stems of every branch on every other plant to try and inhibit stretch. I know the TK will 4x and I’m sure the HPK’s will too. Going to try to keep it around 2.5
Day 15ish (sans timer f’up) for SSDD F2 #4 male
He’s looking good! Got the samsung F-Strips swapped out for one of my QB288 RSpec boards at 60watts here in this 2x2. He’s starting to get frosty
Can see the bulbous trichomes on the leaves and the cystolithic trichomes all over everything else.
Flower development is looking pretty decent imo. If I’m right, he should bulk up with a bunch of dense flowers like the Kryptonite #2 male did. Don’t believe this one will be sparse like the StarShine/Starlite Daydream male was. So far so good
Pollen dropping soon!
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That’s exactly what I was gonna say…
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You can absolutely trust the reading IF you have 22 paper , it’s sold everywhere , got mine at Walmart .
If you don’t believe me you can prove it to yourself. Crank the light put it down on them till you see the leaves come up and pray check the power level in par. Then raise it till leafs just stay horizontal , check reading .
150 par difference between full on pray , which we DONT WANT, or at least I don’t want , and horizontal
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Someone mentioned about a year back that some tropical fish stores have a ‘loaner’ program where they will loan out a par meter so the customer can check and adjust their aquarium light setups.
If you plot out the differences between your setup and a calibrated meter you will have a correction curve you can use in the future.
Cheers
G
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