LED light intensity

giantsfan24 said:

So from this, I'm getting I really should have a par meter. So you have one you'd recommend?

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I never felt the urge to buy a par meter. A lux meter works just fine and costs a lot less.

If you use 3000K 80CRI leds then dividing the lux values by 69 gets you close enough. It's not really an exact science anyway. Plants shoulw be fine with 250umol/s/m2 up to 1500umol/s/m2. A few percent off really doesn't matter

Yes, with a "white" light source HF behaved close to a licor in a yt video. With monos? I'm not sure

Edit.... lux meter can show the same disparities in canopy uniformity with yellow phosphor fixtures...ausb apogee sensor isn't wildly expensive either

Humple said:

And with that in mind, wouldn't you say that your run-of-the-mill lux meter is sufficient? Not sure I see the value of an expensive PAR meter for your average home grower.

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$15 for a lux meter is money well spent for those using white light, especially useful for inexperienced growers.

wietefras said:

I never felt the urge to buy a par meter. A lux meter works just fine and costs a lot less.

If you use 3000K 80CRI leds then dividing the lux values by 69 gets you close enough. It's not really an exact science anyway. Plants shoulw be fine with 250umol/s/m2 up to 1500umol/s/m2. A few percent off really doesn't matter

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Especially because, I mean, I'm not in this to be a commercial grower. I'm just a guy looking to refine the little grow space that I've created for myself. I use 3500 80CRI. Which meter do you use?

CobKits said:

or phone app

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Are there phone apps that are accurate? I didn't even think of that...but I wouldn't lol.

giantsfan24 said:

Are there phone apps that are accurate? I didn't even think of that...but I wouldn't lol.

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I ordered a cheap lux meter and my phone app was not off by as much as I thought on the norm 5-7K lux less than meter so for the sake of even canopy coverage the app will suffice doesn't matter what the figure reads you just want as close to the same figure across the board

CobKits said:

1000 umol of sunlight vs 1000 umol of red-heavy light designed for horticulture do not behave the same way, the former has more of the less-photosynthetically-active components of the spectrum

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Actually, you are incorrect. 1000 umol of photons is the same regardless of spectrum as it is a photon count. Now if you said lux, and that sunlight would be more, then yes, you would be correct.

Plants will use them all, some require less conditioning than others for photosynthesis.

Warranted correction I believe, not intended to start a flame fest over someone making an error.

Evil-Mobo said:

I ordered a cheap lux meter and my phone app was not off by as much as I thought on the norm 5-7K lux less than meter so for the sake of even canopy coverage the app will suffice doesn't matter what the figure reads you just want as close to the same figure across the board

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Then you calculate the par with the conversion factor for the light?

giantsfan24 said:

Then you calculate the par with the conversion factor for the light?

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That's the word on the street

My argument was all the conversion factors if you trace their origins back far enough are based off of non LED lighting. The number used for LED seems to fall in line with the HPS/MH lights in the older charts, so honestly man unless you're a pro that needs a pricey par meter for some reason just use lux and do the math, that's my opinion anyways.

Like example, I use a rubber maid can for watering sometimes and drop a pump in etc. I couldn't tell you how many gallons I fill I just know fro trial and error where to fill it to and how much nutes to add to get where I want from doing it and trying it out. My point is what if the amount is ten gallon, or 12 gallons? Who cares it's a unit of measure. I could say I use X amount of nutes for a unit the unit is whatever I call it honestly. We just have standards of measures for reference and it makes things easier right. Same deal. At the end of the day it's light hitting the canopy and we ideally want one same reading across the entire canopy, so it really doesn't matter what the "reading" is is units, LUX, PAR, PPF, PPFD, whatever we want uniformity. A cell phone app whether it's off on LUX or not will still give you a reading adjust things until your readings are the same and done. You don't need to spend a ton of money on something to "tweak" lights. Most of us (myself included) would get more of an increase in yields from other things that money could go to like a dehu, or A/C, or better intake exhaust, there's other things that will be more of an impact (within reason right). So it cracks me up to see people get so wound up arguing. Go hang alight throw something that grows under it and try different things that's how you learn by doing. And you will be surprised how many things don't always translate straight across from paper to real life. I got my lux meter on amazon for like $11 shipped with prime. Reach out if you need the info. But honestly just download an app and do the math so you understand everything but no need for a pricey par meter for the normal dude growing at home in my opinion.

Just my $0.02

Evil-Mobo said:

That's the word on the street

My argument was all the conversion factors if you trace their origins back far enough are based off of non LED lighting. The number used for LED seems to fall in line with the HPS/MH lights in the older charts, so honestly man unless you're a pro that needs a pricey par meter for some reason just use lux and do the math, that's my opinion anyways.

Like example, I use a rubber maid can for watering sometimes and drop a pump in etc. I couldn't tell you how many gallons I fill I just know fro trial and error where to fill it to and how much nutes to add to get where I want from doing it and trying it out. My point is what if the amount is ten gallon, or 12 gallons? Who cares it's a unit of measure. I could say I use X amount of nutes for a unit the unit is whatever I call it honestly. We just have standards of measures for reference and it makes things easier right. Same deal. At the end of the day it's light hitting the canopy and we ideally want one same reading across the entire canopy, so it really doesn't matter what the "reading" is is units, LUX, PAR, PPF, PPFD, whatever we want uniformity. A cell phone app whether it's off on LUX or not will still give you a reading adjust things until your readings are the same and done. You don't need to spend a ton of money on something to "tweak" lights. Most of us (myself included) would get more of an increase in yields from other things that money could go to like a dehu, or A/C, or better intake exhaust, there's other things that will be more of an impact (within reason right). So it cracks me up to see people get so wound up arguing. Go hang alight throw something that grows under it and try different things that's how you learn by doing. And you will be surprised how many things don't always translate straight across from paper to real life. I got my lux meter on amazon for like $11 shipped with prime. Reach out if you need the info. But honestly just download an app and do the math so you understand everything but no need for a pricey par meter for the normal dude growing at home in my opinion.

Just my $0.02

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Point taken. When I was growing under hid I had my environment dialed in. I've replicated everything from that space with a new box except the light so I'm learning as I go.
Thanks.

giantsfan24 said:

Point taken. When I was growing under hid I had my environment dialed in. I've replicated everything from that space with a new box except the light so I'm learning as I go.
Thanks.

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I came from HID and still mess with both different situations different options work better. Good deal on the environment then you're ahead of the game. You'll be fine.

giantsfan24 said:

Especially because, I mean, I'm not in this to be a commercial grower. I'm just a guy looking to refine the little grow space that I've created for myself. I use 3500 80CRI. Which meter do you use?

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I don't really use a meter at all. Not for that purpose at least. Like I said, the range of intensity which the plants can cope with is huge. So who cares how much it is exactly. You get an estimate from the PPF you get in the specs of the light. PPF divided by your grow space gives you an estimated average PPFD. That's more than enough.

What I did use a lux meter for is to verify that the light uniformity is good (enough).

Besides, if you use COBs well distributed over the grow area, the problem very rarely is caused by the light anyway.

Slinging PAR said:

1000 umol of photons

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Slinging PAR said:

Actually, you are incorrect. 1000 umol of photons is the same regardless of spectrum as it is a photon count. Now if you said lux, and that sunlight would be more, then yes, you would be correct.

Plants will use them all, some require less conditioning than others for photosynthesis.

Warranted correction I believe, not intended to start a flame fest over someone making an error.

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1000 green photons would be measured by a par meter as the same as 1000 red photons

1000 red photons are more usable to the plant.

if number of photons were the only criteria nobody would be using lower color temps in phosphor white, 6500k 70 cri (or blue emitters with no phosphor at all) would be the choice

So then the consensus is as long as I'm close to the correct numbers par wise, based on the specs from the manufacturer, and I've got even light distribution, I should just let they plants tell me if, toward the end of the daily light cycle, I need to adjust the light intensity down as they are droopy and not lacking water or up if the are looking like they are reaching for the light/getting stretchy?

This summation takes into consideration that if the light is too intense the plants will droop toward the end of it's day per a corresponding comment in this thread.

I've got a cam inside the box that allows me to take pics at lights on and off so I can compare at the end of the day. Kind of nice.

CobKits said:

1000 red photons are more usable to the plant.

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Imo this is not 100 % true:
1000 green photons are just as usable to the plant as 1000 red photons from an photosynthetic point of view BUT as the leafs are able to absorb red far better then green, 1000 EMITTED red photons are more useful to the plant....

yes, we are measuring emitted photons of course.

i know of know way to measure absorbed photons other than CO2 balance and nobody is doing that

Schalalala said:

Imo this is not 100 % true:
1000 green photons are just as usable to the plant as 1000 red photons from an photosynthetic point of view BUT as the leafs are able to absorb red far better then green, 1000 EMITTED red photons are more useful to the plant....

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It is actually easier for the plant to use red photons. Outside of the red region, the plant needs to condition photons for PS1 and PS2 (680nm and 700nm) reactions. Lower wavelength photons have more energy which needs to be reduced (heat, other processes) before they can be used. I am not going to say photosynthesis because photon conditioning is part of the process.

If one said that red wavelengths are easier for the plant to use then it would be correct. But photon to photon, the plant will use them all. Well 3-4% of them anyhow.

* note: its is early and I am too lazy to look up the exact numbers

Schalalala said:

Imo this is not 100 % true:
1000 green photons are just as usable to the plant as 1000 red photons from an photosynthetic point of view BUT as the leafs are able to absorb red far better then green, 1000 EMITTED red photons are more useful to the plant....

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Yes..but at intracanopy level still we need a lot of green photons....unless we use red leds intracanopy lights....

CobKits said:

yes, we are measuring emitted photons of course.

i know of know way to measure absorbed photons other than CO2 balance and nobody is doing that

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Plant growth?

Great discussion folks