Recommendation: Cheap PPFD meter?

1212ham said:

The problem is that different phones give different readings, especially Android's.

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When I traded email with Dominik, the programmer at Photone, a couple of years ago, he emphasized that point. The iPhone is a fairly stable platform to write to because there's a limited number of iPhones and Apple has, historically, created products of a uniform quality. That's one of the advantages of a closed ecosystem.

In contrast, Android is wide open - if it can run Android OS, you can market the hardware so there is no way to ensure consistency. That's the heart of the matter. In an email of 4/22/23, he wrote:

"In general, we’re still heavily working on the Android Beta’s accuracy as we’re supporting over 20’000 Android devices and know that factory calibrated accuracy can be a hit or miss. Ideally, the Android version should be calibrated using any of the methods described here: https://growlightmeter.com/guides/how-to-calibrate-photone/ (just FYI, if you encounter any Android user having issues)"

You can make the argument that measuring light levels is so fraught with inaccuracy that it's not such a big deal to be, say, 20% inaccurate and there is some merit to that argument frankly (that statement opens a can of worms, eh?) My counter to that argument is simple - my preference is not to use a $1k device (or whatever) when I can use a $35 purpose built device. Second, rather than spend $5 for a license for Photone, with an unknown level of accuracy, I'd prefer to spend $35 on something that has a known level of inaccuracy.

In contrast, if you calibrate Photone it's got a lot of advantages simply because it's software running on a very portable computer. The website for the product is vastly improved and, according to the programmer and a few other sources, there are hardware devices where Photone is very accurate.

That wasn't my experience, though. In my experience and testing (Photone on my iPhone XSMax), Photone was not able to give me a reading when I tested it against my Kind blurple (from 2017), it does not accurately read the PPFD of the sun, and was >15% off when I tested it using a Mars SP 3000 and compared the results to my Apogee.

hey that was great info on calibrating vs the charts and another device, thanks for sharing!

Update: So I got the UNI-T bluetooth sensor to run with my android PPFD meter app. Turns out my (Motorola) built in phone sensor was less that 20 ppfd different than the UNI-T. So I guess the lesson is that a properly calibrated phone with the ppfd meter app is pretty damn close and (in my case anyway) the uni-t is not really necessary. Just putting it out there.

pegboy said:

Update: So I got the UNI-T bluetooth sensor to run with my android PPFD meter app. Turns out my (Motorola) built in phone sensor was less that 20 ppfd different than the UNI-T. So I guess the lesson is that a properly calibrated phone with the ppfd meter app is pretty damn close and (in my case anyway) the uni-t is not really necessary. Just putting it out there.

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Agreed - you're using the Uni-T as a "known good" device to calibrate/verfiy the value that Photone is displaying. That's a valid approach but that also means that you're using your $$$ phone instead of a $32 lux meter. For me, I'd rather use the Uni-T instead of my iPhone (former paratrooper and artillery officer so I tend to err on the side of caution).

Another reason why I would use the Uni-T bluetooth model is that it communicates with the app that a runs on your phone. That's a big bonus growers because it allows the grower to "sample" the canopy by taking readings at different spots of the canopy. When my grows are in the early stages, I will take light readings on just a few areas of the canopy. As my plant matures (I grow one plant in my 2' x 4' tent), I'll switch to taking readings in a grid pattern. That gives me a very good picture of what part of the canopy is getting how much light.

The data below are from a grow where I was using three lights - a ViparSpectra XS-1500, the Growcraft X3 flower light, and a Mars SP 3000. The blue text indicates low light. The "3" and the "9" are the standard deviation of DLI values the X3 and the Mars (for readings >=45mols). This indicates that my light levels are good for the X3 but the other lights need some adjustment.



Another advantage of using the Uni-T Bluetooth is that it allows a grower to take readings with the text flaps closed vs open. In my tent, the front of the plant gets ≈ 100µmols of additional light when I close the flaps vs leaving them open.

With the Uni-T Bluetooth, a grower can pull the flaps closed, put his arm into the tent, and push the button to take samples. That's doable because the Uni-T has a physical button that the grower presses to take the reading. If the "sample" function were to be available in Photone, it would be more difficult to take samples because there's no physical button on the phone. Last time I tested Photone (a year ago) it didn't have that feature; perhaps it does now. Regardless, lacking a physical button on the phone, it's easier to use the Uni-T BT for sampling than it is to use a phone.

I'm too poor [cheap?] for that stuff.
I have one of those Amazon cheapo 3 way meters. The ph and moisture part are useless but for 8 bucks the light meter function works fine. Honestly I'm not even sure what the scale is reading at. I keep the seedlings around 500, as they leaf out I gradually kick the light up to 1000 on the scale and they grow just fine. I can check any part of the tent in a couple of seconds and get a fairly accurate comparative reading. Anything else is extraneous for my needs.

Delps8 said:

Agreed - you're using the Uni-T as a "known good" device to calibrate/verfiy the value that Photone is displaying. That's a valid approach but that also means that you're using your $$$ phone instead of a $32 lux meter. For me, I'd rather use the Uni-T instead of my iPhone (former paratrooper and artillery officer so I tend to err on the side of caution).

Another reason why I would use the Uni-T bluetooth model is that it communicates with the app that a runs on your phone. That's a big bonus growers because it allows the grower to "sample" the canopy by taking readings at different spots of the canopy. When my grows are in the early stages, I will take light readings on just a few areas of the canopy. As my plant matures (I grow one plant in my 2' x 4' tent), I'll switch to taking readings in a grid pattern. That gives me a very good picture of what part of the canopy is getting how much light.

The data below are from a grow where I was using three lights - a ViparSpectra XS-1500, the Growcraft X3 flower light, and a Mars SP 3000. The blue text indicates low light. The "3" and the "9" are the standard deviation of DLI values the X3 and the Mars (for readings >=45mols). This indicates that my light levels are good for the X3 but the other lights need some adjustment.

View attachment 5331650

Another advantage of using the Uni-T Bluetooth is that it allows a grower to take readings with the text flaps closed vs open. In my tent, the front of the plant gets ≈ 100µmols of additional light when I close the flaps vs leaving them open.

With the Uni-T Bluetooth, a grower can pull the flaps closed, put his arm into the tent, and push the button to take samples. That's doable because the Uni-T has a physical button that the grower presses to take the reading. If the "sample" function were to be available in Photone, it would be more difficult to take samples because there's no physical button on the phone. Last time I tested Photone (a year ago) it didn't have that feature; perhaps it does now. Regardless, lacking a physical button on the phone, it's easier to use the Uni-T BT for sampling than it is to use a phone.

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I like that it has no damn cord! Yesterday that allowed me to set it on a solo cup with a seedling and close the door, DLI increased from 12 to 12.5

pegboy said:

Update: So I got the UNI-T bluetooth sensor to run with my android PPFD meter app. Turns out my (Motorola) built in phone sensor was less that 20 ppfd different than the UNI-T. So I guess the lesson is that a properly calibrated phone with the ppfd meter app is pretty damn close and (in my case anyway) the uni-t is not really necessary. Just putting it out there.

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Well, it was needed to check the accuracy of your phone.
I suggest checking your phone at various light levels, it's probably not linear.

My cheap Samsung is maxed out something like 450 so it's useless for much more than a seedling. That, and reading a phone screen under the glare of a high power LED isn't my idea of fun.

1212ham said:

Well, it was needed to check the accuracy of your phone.
I suggest checking your phone at various light levels, it's probably not linear.

My cheap Samsung is maxed out something like 450 so it's useless for much more than a seedling. That, and reading a phone screen under the glare of a high power LED isn't my idea of fun.

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From the perspective of the programmer, iPhones are easier to deal with. Compared to Android devices, the are far fewer "active" models of iPhones. Also, Apple tends to use the same suppliers year after year. With Android, the situation is very different.

Per the Photone programmer who wrote this on 4/27/22 - "In general, we’re still heavily working on the Android Beta’s accuracy as we’re supporting over 20’000 Android devices and know that factory calibrated accuracy can be a hit or miss."

With all the time that we spend on our grows, it seems to me to be a better approach to spend $30 on something that we know to be accurate ±5% rather than spend $5 on something that could be completely off base.

At this moment, there's a thread on another cannabis forum where the grower is getting a highly incorrect reading from a Vipar bar light. Photone is reporting 964µmols at 75% power at 20". Based on the results published by CocoForCannabis, the actual value is about 400µmols. It could be operator error - I forgot to ask him if he added the kludgy little paper strip over the sensor - but the fact of the matter is that a grower is using Photone and the results are about 100% overstated. Ouch.

1212ham said:

Well, it was needed to check the accuracy of your phone.
I suggest checking your phone at various light levels, it's probably not linear.

My cheap Samsung is maxed out something like 450 so it's useless for much more than a seedling. That, and reading a phone screen under the glare of a high power LED isn't my idea of fun.

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I've kept using the Uni-T. Its nice having my phone outside of the tent while taking readings.

laddyd said:

I'm too poor [cheap?] for that stuff

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My 50$ cheap ass Chinese board I bought has lead me down a path of good quality LED light upgrades (to take some worry of fire away) and a shit load of 50$ tinker toys, in persuit of growing some top notch bud.
But out of all the little knick nacks, actually watching and learning from the plant is gotta be the best way to learn your environment, lighting and feed.
My $700 Photontek only has 25% incremental dial... Though, fcuk I'm gonna need a $300 proprietary controler, a $400 apogee meter ... The $50 option was just verification at time of use, then I let the plant tell me it wanted more and haven't used it since.
TLDR: Learn your plant, light, environment and save your money

dwc420letsgo said:

Photone app

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This

you can debate all you want but Inless ur doing big rooms and some worth while commercial level rooms (talking 1k+ light rooms) this meter isn’t gonnea be used that often and your gonnea know ur sweet spots by first round or even hrs after installed. follow instructions on maker and don’t over do it lol, meaning if it’s. 600-750 watt meant for 4x4-5x5 in veg keep led way higher up (like 30-40+ inches) but also have the led at 30-50% dim t most meaning 300-600 ppfd is jazz . once in flower lower the led to makers suggestions and gradually raise dimmer 50% and every few days raise the dimmer 5-10%, watch pheno’s/plants every 1-3 days and see their response. after getting past 800 ppfd/75%ish dimmer u really need to have room above 78f and co2 above 1000k, I will than suggest with every co2 ur giving feed nutes Inless pheno wants more based on co2 ppm meaning if u feed co2 at 1k , feed at 1k ppm Inless plants show otherwise.

I tried luxx meters, did the app multiple rounds, but really it only showed me being my room is 40ft sog where the ppfd was lacking vs tool to know what to do? It’s really simple and also I used a measurer more often to know canopy distance and % of dim more thn ppfd cause after I followed ocd the canopy distance and suggested dim , whatcha know the ppfd was very close to what was suggested or needed? point is u could have right ppfd but who’s to say ur too close and have too much ir or heat/emviromental stresses and it’s ur first trial or w/e and wonder wtf am I doing wrong? I know this super common but also people want to max their dim/ppfd but not get their enviromental stability to be able to do It right and wonder why their buds are fried/fox tailed Or hermies?

just saying, know ur distance, environmental mediums and watch ur plants health cause just because ur ppfd shows right does not mean the plant likes that or it will work, it’s like saying Someone that’s a body builder will need same intake as a person that isn’t working out, just feed em to max lol . Shoot I saw better yeilds and results def with lower temps, lower dim/ppfd (I lowered to 75%) but also no co2 since low temps (62-70f) but doing that at last 2 weeks vs maxed led/co2 and pumping as much as I could till end?



there’s zero reason even when the light is new to you to be spending $300-500 a ppfd meter, its really not gonnea solve what the makers already suggested and u can’t just read the ppfd and know ur fine without enviromental stability and knowing those and canopy height .

it’s better to just measure the distance from canopy to light and use the maker of lights suggestion based on dim % and distance to canopy . I have used 5+ brands of led’s and even when I did de’s/hps this same rules worked perfectly fine. Big key is to know ur canopy’s true rh/vpd/temps and than factor ur ppfd just on a simple base using a app like Photone or a cheap luxx meter as a measurement of not exact ppfd but knowing where ur overlap and lacking spots is the Main point. When not having huge sqft rooms u can easily figure this out and also know ur issue/vulnerability . I know too many people who buy expensive meters while they’re waiting for their led to be there or first cycle and thinking it will be this golden ticket or show them this secret to sucess. it’s really not complicated but also very visually u can tell if the plants are liking ur levels or stressing. most of the time it’s enviromental instability and people trying to take things to max but also not being patient with graudallly raising the dimmer but also realizing it’s not a bad thing to use less like nutes if the pheno isn’t wanting or desires it?


key with this is watching ur pheno’s on responsive stress to more ppfd (like so many other factors to effectiveness), meaning some def don’t like over 850-950 ppfd that’s fosure. Like nutes you can’t blindly follow makers saying take it to max and closest to distance of canopy without co2 and environmental instability and not ask for bad results.




environment guides worth looking

Look's like PPFD Meter app is available also for iPhone.
Does any one have tried it?

mimosa17 said:

Look's like PPFD Meter app is available also for iPhone.
Does any one have tried it?

PPFD METER - Grow Light Meter

The only grow light meter app you need to set your grow lights correctly. Create PAR Map and Measure PAR / PPFD, DLI, LUX with your Android phone. Including PPFD meter and DLI conversion for plants.

www.ppfd.app

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Use Photone on the iPhone, nearly as accurate as an apogee meter

Greengrouch said:

Use Photone on the iPhone, nearly as accurate as an apogee meter

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I use photone on my Samsung. If it's not accurate I wouldn't know, but my plants seem to be happy at around 700-900 ppfd.

A $20 Uni-T lux meter is within a few percent of an Apogee MQ-500 PAR meter as tested by Shane from Migro.
More than enough accuracy for anything this side of NASA work.

Billy the Mountain said:

A $20 Uni-T lux meter is within a few percent of an Apogee MQ-500 PAR meter as tested by Shane from Migro.
More than enough accuracy for anything this side of NASA work.

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Yea, much easier than sliding your phone and head around under a light, and no guesswork on the readings.

This one works well for me. Pretty close to the photon app results on my pixel and my wife's iphone.

I use them to set the distance, not so much to check the strength if that makes sense.
Quantum PAR Meter Full-Spectrum High Precision PPFD Tester for Photosynthetic Activity of Indoor and Outdoor Plants 400-700nm Light Lux Tester https://a.co/d/fiSmNNj