Watts vs PPFD: which do you use?

The70’s

The70’s

Well-Known Member
So, since im new to growing im exploring more and more. Sometimes it’s important, sometimes its not. I thought my watt meter and a yard stick was all i needed to dial in my grow lites.

How do u measure your lites, how do you get it at least what your plants need at any given phase.

New grower here go easy Lol
 
The70’s said:
So, since im new to growing im exploring more and more. Sometimes it’s important, sometimes its not. I thought my watt meter and a yard stick was all i needed to dial in my grow lites.

How do u measure your lites, how do you get it at least what your plants need at any given phase.

New grower here go easy Lol
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It's actually a very good question. I have a meter that measures LUX and I have researched out the LUX levels needed at various stages of growth. I set my lights accordingly either by height or by using the dimmer switch.
 
If I had an Apogee SQ-610-SS Series sensor (and associated meter) to measure the ePAR output, I would use it, every time.

Not being able to defecate gold nuggets, I grab the manufacturer's PAR maps, mix hope and trust with a pinch of skepticism, salt liberally with common sense, and try to extrapolate well enough to estimate what's going on in my space (which often differs from the size/shape that was used to produce the map(s)/charts).

When adjusting the wattage of a device, I use my Kill A Watt if it's not hiding, even if the adjuster is a simple five-position switch and I "know" that setting 4 should be 80%. Because fool me once, lol...

What I don't use are eyeballs, version 1, human. Because "pretty bright" does not grow trees.
 
Same here, I use a LUX meter and the dimmer switch to dial in the light.
You can get a LUX meter fairly cheaply on amazon, like 10 or 12 dollars...
 
@Carcass @TorturedSoul @Emilya

Ok, what reference guide for the correct lux or par numbers and height of the light ?? Im shooting in the dark here, my first plant i squished with light that was probably too intense.

My guess, i would set the lites at a couple feet above the canopy , and then dial in my dimmers, also taking note of the height and watt rating for my next run, i think…..

Here is a quick google search
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Every light is different, so we really can't answer your questions. I built my own LED light one time, and I had a need to answer all the questions that you are now asking. Here is how I did it.

LUX, Wattage & Distance Analysis: 6x CREE CXB3590 Array

This is a graph that I compiled tonight based on extensive measurements of my new COB array. I have tested the LUX hitting the table at 30", 24" 18" and 12" and I have tested it at 10w intervals from 15-245w per side, which equates to 5-81w per COB chip. The colored sections of the chart show...
www.420magazine.com
 
1,000 µmol (PPFD) in flowering phase (photoperiodic strains). Probably a little less, if temperature is less than mid-80s (F). More, if you're adding CO₂ and temperature is somewhat higher.

This is why spending a huge amount of money on a high-powered light isn't always the best idea. Many of them do produce a huge amount of light-energy - but it's concentrated in the region directly under the light, and near it. Therefore, you might end up with too much in the middle of your garden, in an attempt to properly illuminate the perimeter. Multiple lower-powered light sources allow you to spread the light-energy out. And, with proper placement, the "drop-off" zone at the edge of one light will also be the "drop-off" zone of the next light, which means that that area will be receiving some light from each (and that might total enough light-energy). We used to refer to this as the third-light effect, but I don't know whether that term is still in common use.

Note that I am talking about the more common type of LED grow light products that have a relatively large number of diodes close together. Some products consist of multiple panels - and this, in effect, does the same thing as buying multiple lower-powered LED panels. And there are products that have their diodes in rows, on bars/rails/whatever, which also try to do the same thing (with varying degrees of success

If plants' leaves start looking "bleached," I'll assume that they're receiving too much light. (Burnt isn't a sign of too much light, it's indicative of too much heat; that's what fans are for.)

Growth phase - I don't put much thought into it, lol. 50% more "daylight" hours, so assume my target is roughly 2/3 what I hope to flower with (not 1/2). But that's flexible, because I'm (generally speaking) not in a hurry, at that point - it's not going to do me any favors is the plants get too large... and they'll be in the "stretch" for approximately the first 40% of the flowering phase.

My comments reflect my opinions. Your mileage may vary, as they say. . . .
 
you guys save me a question thx I have all kinds of gadgets but I use a app PPFD meter on my android it gives lux and PPFD and is very accurate
I m not sure if I can post this link or not if not I apologize in advance PPFD METER save ya a couple bucks
@The70’s Thanks for the chart not only did I get a question answered My lights are right where they need to be it is a good day on the farm :rollit:
 
I picked up a cheapie on ebay last nite, DrMeter LX1330B. Im not hoping to be perfect, i just dont wanna be on the fringes of disaster during my first grow.

Thanx for the input
 
ppfd is the preferred measurement now.

generally if you keep to the suggested heights you need nothing. i worked with light meters in my side gig and have never found i needed them for growing.

i still use a rough watt count to determine the size of the light.
 
I created my own using a Lux meter. I have something in the works, using a different lux meter that converts perfectly to most new lights, giving perfect Par measurements. Even ball park figures are 50% better then the garbage hyrofarm PAR meters they sell for $170 on the Zon, theft.

This one pictured is dead on with apogee Epar 610 model. $610

4.5ftpar.png
 
The problem with cheap meters and cellphone apps is that every brand of light will register differently. Depending on the CRI of the light being emitted, our meters are still only approximations. You can get close by knowing the numbers you want to have for that stage of the grow, and then go from there, experimenting and watching as you try to adjust for the maximum light you can give your plants without harming them.

A prime example from my grow rooms is what happens under my @NextLight MEGA. This thing is insanely bright, but I can't believe the LUX reading that my $40 amazon meter is giving me... it claims I am getting 98k LUX at the very top of my canopy. Nothing would be living in that space if that were true... My MARS light reads differently and my COB array does too. Each set of readings can not be compared to the others in the rooms.

A good meter can correct for all of this, and supposedly some of the better apps that you have to pay for can too. So for me, the meter gets me close, and then it is between me, the plants and the light, and I watch like a hawk to see how they react. I could go out and spend $1000 on a good meter, but why? I have eyes.
 
Mayne said:
This one pictured is dead on with apogee Epar 610 model. $610
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can't go wrong with an apogee. that was our go to for closed sets and television.




Emilya said:
A prime example from my grow rooms is what happens under my @NextLight MEGA. This thing is insanely bright, but I can't believe the LUX reading that my $40 amazon meter is giving me... it claims I am getting 98k LUX at the very top of my canopy. Nothing would be living in that space if that were true... My MARS light reads differently and my COB array does too. Each set of readings can not be compared to the others in the rooms.
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led and different led emitters register different as they are very narrow in kelvin. the k effects the type of light, but the meter measures more broadly.

measuring led output with any type of a meter has been an issue since day one.
 
yeah, but most of the new board/bar style lights are generally in the same ballpark. and alot of growers are giving them to much light.
 
Sounds like im gonna be in the ballpark if i hit the middle on the acceptable Lux readings.
Btw totally OT my watering is now about a nice balance and my bigger plant is using a good Red Solo cup of water every 36hrs.

Another thing, i can see my smaller girl stretching for the lite a little more than my short fatty girl Lol, this trial and error is right up my alley, i love experimenting
 
Mayne said:
yeah, but most of the new board/bar style lights are generally in the same ballpark. and alot of growers are giving them to much light.
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i run heavy led and would probably fall in to that category. i don't believe in too much light. give them everything and use a dimmer.

i run 600w of cob led in a 4 x 4. going to a 650w qb/strip style soon.
 
I think the most mine will push is about 425watts in my 4x4, rite now i have the lites at 150watts and about 29” away. They seem very green and happy, i gotta go to a bigger pot soon for the bigger of the two

They are quantum 301 boards i got off ebay a couple years ago, there is one powersupply to each two them
 
Mayne said:
whats your lux at canopy? YOU know what your doing, i seen your grows. COBS are great, i liked mine too
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i have no idea what mine are putting out right now. we did meter them when i first built it, but i can't remember the numbers. i remember thinking it looked like more than what the meter got. i'm flower biased though, i run 3500k and 3000 which gets pretty far red. it makes a difference. the light is very much the same as an hps.

the new light is more 'full spec'. i'm a little nervous as i'm not sure how it will perform in flower.
 
The70’s said:
So, since im new to growing im exploring more and more. Sometimes it’s important, sometimes its not. I thought my watt meter and a yard stick was all i needed to dial in my grow lites.

How do u measure your lites, how do you get it at least what your plants need at any given phase.

New grower here go easy Lol
Click to expand...
The only true way to "measure" a light is by using PAR and PPFD as it directly relates to the photons available for a plant across a growing surface that are used for photosynthesis.

Watts, although a good "General Reference", does not relate to any cannabis and only can be used as a very very general guideline for choosing a light based on its draw wattage and the space you are using... It really is a bad way to judge lights because a 250w light by one mfg, can be completely different in actual light output than another 250w light... so watts is only a good broad reference, nothing more. (efficiency, beam angle, reflectors, lenses and mounting height) all could make (2) different 250w lights completely different in the way they output light.

Lumens and Lux are poor ways of judging light for plants, and also can only be used as a very general reference. (for many growers this is ok) such as looking for shaded areas vs well illuminated ones. But Lux and lumens are not good for plants because they are weighted on a green light scale for human eyes, and have zero correlation with actual plant processes. Also, because lux is based off visible light and weighted towards green, different spectrums and color temps effect how the conversion to PAR is calculated, therefore it is more of a general reference than a specific measurement.


Watts, Lux and Lumens are NON plant specific measurements and should only be used for very general reference, where PAR, PPFD and DLI are plant specific measurements that are used by professional agriculture.


Also you don't need a PAR meter or any type of measurement tool unless you are testing lights or running a professional facility. Every reputable LED and Grow light manufacture should absolutely be able to provide you a 4x4 PAR map with measurements at different heights for each of their products. Without making it too complicated for veg under 18/6 you want around 400-700 umol/m2/s-1 (PAR) and for flowering under 12/12 you want to see around 900-1200 umol/m2/s-1 (PAR) without CO2, and if you are using supplemental CO2 in flowering then you can go up to 1500-2000 umol/m2/s-1.
 
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