Understanding light.

Farmer P · Dec 29, 2019

MIMedGrower said:
They have proven that plants use plenty of green spectrum. It penetrates deeper into the canopy. And it sparks photosynthesis like all the other usable light. I think the reflecting off of the leaves is how it penetrates dense foliage. Only some is reflected.

Plus leaves are not solid. They are more of a screen or membrane to light. Some is absorbed and some reflected from all color spectrum.

I agree with what you said, I just didn't like how he was acting like it was a mystery why people would think the plant doesn't use green. Seems obvious why they thought that to me.
Edit: Sorry for the bad English.. To me it seems obvious why people thought that green light wasn't used by plants.

MIMedGrower · Dec 29, 2019

Farmer P said:
I agree with what you said, I just didn't like how he was acting like it was a mystery why people would think the plant doesn't use green. Seems obvious why they thought that to me.

I probably should watch the video. Lol. ;-)

Farmer P · Dec 29, 2019

This guy seems to think that everyone before him was retarded notwithstanding the fact that they did'nt have the technology to prove what has recently been proven. He should have said so. It would have been better to give accolades to the people whose work he has built upon and admitted that technology has now shown that what was formerly believed is not exactly so. Instead he shits on all who came before and acts like he is a genius. Just my take.

MIMedGrower · Dec 29, 2019

Farmer P said:
This guy seems to think that everyone before him was retarded notwithstanding the fact that they did'nt have the technology to prove what has recently been proven. He should have said so. It would have been better to give accolades to the people whose work he has built upon and admitted that technology has now shown that what was formerly believed is not exactly so. Instead he shits on all who came before and acts like he is a genius. Just my take.

I scanned through it now. Nothing new there but quality info discussed.

I think its more that he had argued with his peers in the industry about it a long time. Scientists get an ego going like anyone.

Only problem is NASA already has papers on all this. But the U of M is huge on grow light research.

Hidd3nGr0w · Mar 4, 2020

Thanks again for the point in the right direction @BigCube

Hidd3nGr0w · Mar 4, 2020

No sun out today, I am curious what the lux reading is for natural sunlight.

Check me and make sure I am processing this correctly. You had 45k lux being the threshold for aggressive veg flower. Would being in the 30k to 40k range be considered a normal flower range. Seems like the higher numbers are going to burn more nutrients as well, so would a soil grower be better off staying below a certain threshold?

Just trying to process the info, took some readings yesterday with my lights and was in the 18k/19k range at 24" in flower, I might be able to drop the light to 18" but I know heat will start to become an issue. A better lighting source is on the way. Just wondering how you ramp up to that 45k threshold? Do you start at say 20k and then adjust up 10k every week till you hit the 55k average for aggressive flower and then micro manage it after that up or down?

Thanks for the tips, much appreciated.

BigCube · Mar 5, 2020

Hidd3nGr0w said:
No sun out today, I am curious what the lux reading is for natural sunlight.

Check me and make sure I am processing this correctly. You had 45k lux being the threshold for aggressive veg flower. Would being in the 30k to 40k range be considered a normal flower range. Seems like the higher numbers are going to burn more nutrients as well, so would a soil grower be better off staying below a certain threshold?

Just trying to process the info, took some readings yesterday with my lights and was in the 18k/19k range at 24" in flower, I might be able to drop the light to 18" but I know heat will start to become an issue. A better lighting source is on the way. Just wondering how you ramp up to that 45k threshold? Do you start at say 20k and then adjust up 10k every week till you hit the 55k average for aggressive flower and then micro manage it after that up or down?

Thanks for the tips, much appreciated.

I havent actually measures the summber mid day sun. But I assume it's around there. Once you get up around 80k to 100k (strain and heat depending) you start to need Co2 supplementation.

I usually dont go past 80k for a very aggressive flower. Below 50k ish is enough to give you good results, but the truly great results (I have found) come at above 60k. Play with it some. Measure the lights you already use, and use them as a guide.

Snakeskins · Mar 5, 2020

Ok, so a list of lux values to look for when I get the approximate numbers from an app. Right on. Thanks @BigCube. I read everything else too :). Very well explained.

Homesteader · Mar 5, 2020

Using Lux as a measure is not a very accurate approach and gives you a false sense because it is weighted heavily towards yellow and green.
Lux is for the human eye.

I run a lot of red light and if I used lux as a measure, it would read a fraction of that light.

BigCube · Mar 5, 2020

Homesteader said:
Using Lux as a measure is not a very accurate approach and gives you a false sense because it is weighted heavily towards yellow and green.
Lux is for the human eye.

I run a lot of red light and if I used lux as a measure, it would read a fraction of that light.

View attachment 947368

Sounds like you didn't read my post at all....

Why don't you you measure your nutrients in u mol? Why do you demand such extreme accuracy for light, but not nutrients? Ppm and ec are also weighted in that same sense.

You cannot increase lumens without increasing par, and vice versa. There are actual formulas that will give you accurate par numbers when you compensate for the light temperature.

The plant uses yellow and green JUST AS MUCH as all the other colors. If you know what your spectrum looks like (you should, manufacturers supply them) then you know where the "weight" is. There is even math you can do to accurately convert one to the other using the light temperature as a variable...

Are you saying we should all go out and buy $1000 par meters? If so, what actual benefit do you expect it have? As in real world application for your grow.

Homesteader · Mar 5, 2020

I think I read all your post on here. I don't agree with all of it. So be it.

Hydrofarm has a decent PAR meter for $100. You don''t need a $1000 measure for a small grow.

Lux is not a decent measure for plants. Period. Plants CAN use green and yellow yes, but it is not as much as red and blue.
Run a grow with just green 530nm and see what happens.

Snakeskins · Mar 5, 2020

Don't know if it matters or not but I'm using a 1500 COB panel (250 true watts) and it's just white-reddish light.

BigCube · Mar 5, 2020

Here, a thought experiment. Using the formula these all have a reading of 1000 lux:

3000k 19.03 umol/s/m2
4000k 17.82 umol/s/m2
6500k 17.23 umol/s/m2

The range most grow lights are in..
1.8 difference, at the extreme.. less than 5%

I agree adding red is good. I said as much. And I referenced what I do for red. If you want to measure the red as well, do the calculations for it separately. Manufacturers specs will give you lux or lm levels. Just calculate it out...

For example 1000 lux of monochromatic red at 650nm is 76.85 umol/s/m2

Save your money man, use your head meat instead

BigCube · Mar 5, 2020

Homesteader said:
I think I read all your post on here. I don't agree with all of it. So be it.

Hydrofarm has a decent PAR meter for $100. You don''t need a $1000 measure for a small grow.

Lux is not a decent measure for plants. Period. Plants CAN use green and yellow yes, but it is not as much as red and blue.
Run a grow with just green 530nm and see what happens.

I suggest researching it, they do use green and yellow just as much as blue.

As for hydrofarms par meter...
Just go reat amazon reviews.. they are %100 shit. Even if you get a working one, they fall out of calibration fast. If you want a reliable accurate par meter they are not cheap. And a hydro farm isnt $100. Its $200.

Hydrofarm LGBQM Quantum Par Meter Micromol Sensor

Homesteader · Mar 5, 2020

I don't use loonies. Its around $100 here in the US.
Ebay has some used ones for under $50

Homesteader · Mar 5, 2020

Why would I care what amazon reviews say? Honestly how many of those people know anything about anything?

Ill tell you right now the battery sucks on the Par meter but its accurate enough to do read your light well.

Measuring grow light indoors generally is about getting an even canopy. So in that sense, if you want to get a lux meter, I'm sure it would suffice and make sense to do so.
Ill agree to disagree about green light. I have no interest in arguing about such things.

BigCube · Mar 5, 2020

Homesteader said:
I don't use loonies. Its around $100 here in the US.
Ebay has some used ones for under $50

Yeah, maybe in the US you could find one for $100. But the fact is, they arent good and are very untrustworthy. But that's all beside the fact, it's not necessary.

Can you give me one actual real world benefit of using par? Like what does your $100 get you?

BigCube · Mar 5, 2020

I've seen and heard of many people testing hydrofarm meters against lab equipment. It never ends well.

Homesteader · Mar 5, 2020

For most growers, I wouldn't recommend getting either. You can tell how much light a plant is getting by just looking at it. However if you build your own lights and like experimenting like many do around here, I would get an accurate measure

Dan789 · Mar 5, 2020

Hidd3nGr0w said:
No sun out today, I am curious what the lux reading is for natural sunlight.

Check me and make sure I am processing this correctly. You had 45k lux being the threshold for aggressive veg flower. Would being in the 30k to 40k range be considered a normal flower range. Seems like the higher numbers are going to burn more nutrients as well, so would a soil grower be better off staying below a certain threshold?

Just trying to process the info, took some readings yesterday with my lights and was in the 18k/19k range at 24" in flower, I might be able to drop the light to 18" but I know heat will start to become an issue. A better lighting source is on the way. Just wondering how you ramp up to that 45k threshold? Do you start at say 20k and then adjust up 10k every week till you hit the 55k average for aggressive flower and then micro manage it after that up or down?

Thanks for the tips, much appreciated.

Lux today, my latitude, Northern California around 75000 lux, not yet noon, plus sun is still low in the sky. Just for comparison, measured my four cree cob light, my clones are under, 50000 lux at the canopy about 14” below the lights.

Understanding light.

Understanding light.

Farmer P

MIMedGrower

Farmer P

MIMedGrower

Hidd3nGr0w

Hidd3nGr0w

BigCube

Snakeskins

Homesteader

BigCube

Homesteader

Snakeskins

BigCube

BigCube

Homesteader

Homesteader

BigCube

BigCube

Homesteader

Dan789

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