Cheap Accurate PAR Readings

[MindSoup]

I've touched on this subject quite a lot recently so I thought it would be useful to make a thread to direct people to in the future.

 

With LEDs becoming more and more popular PPFD ,PAR and DLI are becoming a more commonplace topic. With most lights from reputable brands you can easily find an accurate PAR map to help you hang your lights at the optimal height. But, if you have a light from a less reputable brand or perhaps a custom setup you won't have that luxury. Keeping track of light intensity is something that I have found pretty essential when diagnosing issues, especially when working in smaller spaces. There are a few apps out there but a lot of phones have light sensors that max out way to early to be useful and proper PAR sensors are beyond a lot of budgets. Luckily good old Migro on the tube, has made a few guide video's using affordable lux meters and comparing their results to his apogee sensor so you can save a lot of money with a little bit of maths (I got my UNI-T meter for £14!)

 

 

 

 

 

Edited October 20, 2021 by MindSoup

[mysticriver]

28 minutes ago, MindSoup said:

a few apps out there but a lot of phones have light sensors that max out

You have to use a piece of 80gsm paper over the phone camera lens - the Photone app on the iPhone tells you how to do it - thats what I use and its accurate. 

(Its £4.99 for the LED unlock on the app)

 

 

mysticriver 

[MindSoup]

@mysticriver The problem with phones is they all have different sensors which will all give out slightly different readings, so what works for one doesn't necessarily work for another which makes a universal guide impossible. Introducing a piece of paper will only make things less accurate, if you hold a bit up to the light you can see the patchiness of the light coming through, as I move the paper on too of the phone I cam see the reading change. Using a cheap lux meter takes those variables away and makes the whole thing a lot more simple.

 

If you're happy with your methods crack on, I'm not saying it doesn't work well enough for you in your situation, but personally I see this as the best compromise between price and accuracy.

Edited October 20, 2021 by MindSoup

[catweazle1]

Phones are reflected light meters, when you really need is an incident light meter, which measures light falling on the surface. PAR meters, I think, just read PAR light and not all wavelengths. 

[MindSoup]

@CatWeazle I didn't know about the sensors actually working differently but looks like another reason to buy a dedicated meter. Yes PAR meters only measure PAR (photosynthetically active radiation) and are of course the best thing to use albeit uneconomical for most small scale growers, but by simply multiplying the reading from one of the cheap PAR meters in the video by X amount you can convert it to an accurate PAR measurement, happy days. 

[catweazle1]

@MindSoup With an photographers incident light meter held at the canopy, I would think anything around  F16 at 125sec at 100ASA would be reasonable.

[Guest]

6 hours ago, MindSoup said:

@CatWeazle I didn't know about the sensors actually working differently but looks like another reason to buy a dedicated meter. Yes PAR meters only measure PAR (photosynthetically active radiation) and are of course the best thing to use albeit uneconomical for most small scale growers, but by simply multiplying the reading from one of the cheap PAR meters in the video by X amount you can convert it to an accurate PAR measurement, happy days. 

I use UNI-T UT383BT bluetooth Digital Luxmeter cost around £22+- delivery and then multiply on 0.017 to get accurate PAR. 0.017 took from Shane's (MIGRO). Working well 

[Gaijin]

@MindSoup Morning mate   You may have noticed that I've been trying to research myself to death prior to spending thousands in order to grow a weed indoors. Maybe, maybe not. But I have  

 

I've been adding things to my shopping list for months, and taking things off for months too   I didn't think that a first-timer like myself needed PAR meter. Not just yet.

 

But if it's as simple as @Canna Denfour20 £22 then multiply by 0.017 - why the hell not? Of course, I'll need to know what kind of light levels are recommended for what stage of growth. Maybe there's a nice chart somewhere that lays it all out in simple terms for me  

[MindSoup]

Yes mate I have noticed you must be getting lost in it all by now, I know I do. As a relative beginner to indoors and a fellow overthinker I've really found it useful to be able to know for sure what my PPFD is and rule it out as a potential cause of issues, there's a lot of things than go wrong and at first it's hard to know whats causing what. For me it's even more important as I have such little head room. Like you say its so cheap of a tool why not have one. I got mine from ali express for 14 quid!.  

 

Migro and Bruce Bugbee have everything you need to know about lighting, I'd suggest sticking with Migros website and YouTube channel to begin with. Bruce goes pretty deep, and without the basic knowledge it can quickly become an information overload, he's also not great and dispensing the information, I have to watch and re watch his material to really absorb it all, its more information that you would need if you where doing a huge commercial grow. Migro tends to provide  the basics and home growers rules of thumb that and presents the information in a way that's easier to absorb. 

 

Off the top of my head (so probably wrong ). 300ppfd is about minimum for ganja to grow well, 500 is ideal for veg, and 700-850 for flower, you can push it higher without causing stress, but you get a diminishing return on the rate of growth vs the cost of electricity. CO2 enrichment (in a sealed environment) allows for much higher (upto 2000 or so) light intensity, but it costs a lot of money, again something to be left to the commercial guys. 

Edited November 24, 2021 by MindSoup
Make things read easier.

[Gaijin]

Just now, MindSoup said:

Yes mate I have noticed you must be getting lost in it all by now, I know I do.

 

I've almost sold this house 4 times now, and had a final shopping list ready each time. And it's fallen through each time  Number 5 looks like a go, so hopefully only a few more weeks of changing the damn shopping list. Fortunately I like to think that my shopping list has improved over time, like a fine wine  

 

Just now, MindSoup said:

 

Migro and Bruce Bugbee have everything you need to know about lighting, I'd suggest sticking with Migros website and YouTube channel to begin with. Bruce goes pretty deep, and without the basic knowledge it can quickly become an information overload, he's also not great and dispensing the information, I have to watch and re watch his material to really absorb it all, its more information that you would need if you where doing a huge commercial grow. Migro tends to provide  the basics and home growers rules of thumb that and presents the information in a way that's easier to absorb. 

 

Off the top of my head (so probably wrong ). 300ppfd is about minimum for ganja to grow well, 500 is ideal for veg, and 700-850 for flower, you can push it higher without causing stress, but you get a diminishing return on the rate of growth vs the cost of electricity. CO2 enrichment (in a sealed environment) allows for much higher (upto 2000 or so) light intensity, but it costs a lot of money, again something to be left to the commercial guys. 

 

Migro's definitely closer to my level of understanding, at least for now  

 

I'm looking at an HLG RSPEC, that has a PAR map with a 900 in the middle and obviously lowering as you move out towards the edge. So that would be about the max one would want to use, unless you were supplementing CO2 and upping the feeds, yes? I'm also thinking about the Scopex 900, as that has been recommended for a 5x5 and is obviously popular around this place, But at full power, the 900 seems to have a 3x3 square in the centre of the PAR map, that's 1000/1100+ So would that be too much? Would I be buying a light that I would never turn on to full power? Or would I use full power but raise it? In which case, there's no point me buying a light that goes anywhere much above 900.

 

 

Damn shopping list, can't make it's damn mind up  

[MindSoup]

Must be frustrating but as you say it's given you plenty of time to choose the right options. People often rush into growing without research and end up having to re buy all their kit. 

 

I think 1000 in the middle is what Migro uses to find optimal hanging height so not too much no, it's just at above that number the curve starts to level off i.e. the extra cost in electricity isn't worth the gains in yield you get from it and eventually it will cause stress (at about 1500 iirc) without adding CO2. You can always adjust height or the dimmer switch as well ( hence the little lux meters coming in handy).Keep watching those videos mate.

Edited November 24, 2021 by MindSoup

[Gaijin]

8 minutes ago, MindSoup said:

Must be frustrating but as you say it's given you plenty of time to choose the right options. People often rush into growing without research and end up having to re buy all their kit. 

 

I think 1000 in the middle is what Migro uses to find optimal hanging height so not too much no, it's just at above that number the curve starts to level off i.e. the extra cost in electricity isn't worth the gains in yield you get from it and eventually it will cause stress (at about 1500 iirc) without adding CO2. You can always adjust height or the dimmer switch as well ( hence the little lux meters coming in handy).Keep watching those videos mate.

 ok that makes sense   thanks mate

[Gaijin]

I found it!!! 

 

Apparently when I bookmark something important, like this thread, .......... I don't bookmark it at all  Been looking on and off for days now. Pretty sure it was @Exhale that started the thread. It wasn't. I might need a tolerance break  

[BilgePump]

On 24/11/2021 at 1:04 PM, MindSoup said:

People often rush into growing without research and end up having to re buy all their kit. 

 

 

This was me , bought a black orchid tent kit on scamazon.

Didn't take very long to realise a 400w hps is overkill for an 80x80 tent as within hours of firing it up (that first time you switch on hid lighting , jeez my bum went wobbly and I was convinced the whole town saw my window illuminate due to the mini sun I'd just angered)

It had cooked the top 4 inches off my plant I'd been window growing.

Cue my first if accidental foray into topping 

 

I wish I'd done as much homework as you @Gaijin , could have saved a small fortune i 

reckon.

 

[Gaijin]

14 hours ago, BilgePump said:

This was me , bought a black orchid tent kit on scamazon.

Didn't take very long to realise a 400w hps is overkill for an 80x80 tent as within hours of firing it up (that first time you switch on hid lighting , jeez my bum went wobbly and I was convinced the whole town saw my window illuminate due to the mini sun I'd just angered)

It had cooked the top 4 inches off my plant I'd been window growing.

Cue my first if accidental foray into topping 

 

I wish I'd done as much homework as you @Gaijin , could have saved a small fortune i 

reckon.

 

 

Fingers crossed, exchanging house contracts in the next couple of days, then someone in the chain needs to give their work a month's notice. So should be moved by about this time next month, and I can order the bulk of the gear   The research has been fun, mate lol. The shopping list has changed almost every day since about May. Yesterday I deleted the two AirComforts, AGAIN, and reinstated a couple of Govees AGAIN   I still have the Sensor Push in my big river basket. I've almost had TOO long to chew these tiny details over   Just want to get some damn seeds wet mate   

 

And you're not wrong. Research, but mainly this place - saved me a fortune in crap that I would've had to replace or just didn't need in the first place