PAR measurement thread

[wietefras]

Yeah, I'm trying to guess why you keep spamming this bullshit all over the forum.

Indeed it's obvious that you simply "stand behind your claims" regardless. It can't be too hard to read the cannabis related charts and see that your generalized school children biology book chart is not applicable the way you thought it was.
.
Here is some "education" that I have had. Maybe it can help you too:


Still, this again just a generalized example and not two single light response curves which apply to all plants. Cannabis can use even more light than the plant in this example.

 

[PhotonFUD]

Yeah, I'm trying to guess why you keep spamming this bullshit all over the forum.

Indeed it's obvious that you simply "stand behind your claims" regardless. It can't be too hard to read the cannabis related charts and see that your generalized school children biology book chart is not applicable the way you thought it was.
.
Here is some "education" that I have had. Maybe it can help you too:
View attachment 3789186

Still, this again just a generalized example and not two single light response curves which apply to all plants. Cannabis can use even more light than the plant in this example.

This looks like fun to play with, please post more.

Your chart actually supports my position. Since my chart references the rate of photosynthesis, and your's references the net CO2 uptake, the data in your chart would suggest it is from a plant that isn't very very efficient at absorbing light or one that is very efficient at CO2 uptake. Without further information, such as a reference to the study or the document, it is unknown what other factors or testing method was used.

That is why I make sure that the references I use are publicly accessible and from reputable, credible sources.

Anyhow, next?

 

[wietefras]

OK seriously, you are just trolling right?

 

[PhotonFUD]

OK seriously, you are just trolling right?

What do you mean?

I am just pointing out obviously incorrect, or in your case incorrectly used, information. If that upsets you then maybe you should move on to something else.

 

[wietefras]

I guess for a troll like you it makes sense though. When you are growing under a bridge (as trolls do), you would be limited to shadow leaves really.

 

[PhotonFUD]

I guess for a troll like you it makes sense though. When you are growing under a bridge (as trolls do), you would be limited to shadow leaves really.

So you are upset then. Sorry to hear that, maybe you can do better on other topics.

 

[Rahz]

"an accredited university which happens to show a chart where the photosynthetic rate increase peaks ~400 umoles."

The "rate of increase" of the photosynthetic response goes up with lower PPFD but I'm not sure if there's a minimum where that doesn't hold true. The "photosynthetic response" goes up with higher PPFD, flatlining around 1500, though there's some ambiguity about how the curve is affected indoors. It certainly doesn't max out at 400 though. Anyone who has grown with near 400 and much higher knows this is true.

 

[AtterStiga]

Will you double the yield by doubling the light? Perhaps to a point, and that would be the point of highest light efficiency. But you'd still get more by increasing, for a long time. Cost/g would increase, from very fucking low to just fucking low. Cost from electricity, obviously, most other factors would have less impact, like infrastructure which doesn't change.
I can live with diminishing returns for a long time as long as the returns keep on being good. I want to cramp in as many photons as possible without harming the girls. I definitely don't want to give them DLIs of 17 like the 400ppfd. 17 is pretty good for lettuce. 800 is 34.5ish, so a lot better. 1000+ is unknown country for me yet but not for long.

 

[goofy81]

Having read a little bit of this thread, I understand what this guy is trying to say. But with growing as we all know it's impossible to get even light to every single leaf on the plant. Here are some of the reasons "I" wouldn't aim use only 400ppfd.

1. It's not hard to get 800ppfd+ for these days, so why not?
2. 400 at the tops means even lower at the second canopy/layers. Why lose potential yield?
3. Space, most people have limited space, and the space they do have they want to maximize yield.
In the end, it's sometimes not all about efficiency but the end game $$$.

 

[wietefras]

Will you double the yield by doubling the light? Perhaps to a point, and that would be the point of highest light efficiency. But you'd still get more by increasing, for a long time. Cost/g would increase, from very fucking low to just fucking low. Cost from electricity, obviously, most other factors would have less impact, like infrastructure which doesn't change.
I can live with diminishing returns for a long time as long as the returns keep on being good. I want to cramp in as many photons as possible without harming the girls. I definitely don't want to give them DLIs of 17 like the 400ppfd. 17 is pretty good for lettuce. 800 is 34.5ish, so a lot better. 1000+ is unknown country for me yet but not for long.

Exactly, 400 is by no means the saturation point. Not for photosynthesis, not for leaves, not for entire cannabis plants.

I've posted this already in the other thread. It's a chart of the results of 175 grows from the YOR website. The red line is a smoothed average:


Clearly lights well up and over 1000umol/s/m2 will work just fine.

 

[wietefras]

Having read a little bit of this thread, I understand what this guy is trying to say. But with growing as we all know it's impossible to get even light to every single leaf on the plant.

Even his changed interpretation makes no sense, since leaf tests have shown that single cannabis leaves can use even 1500umol/s/m2 just fine.

Besides he never made the claim before and simply said that we should aim for ~400umol PPFD with our lights.

 

[AtterStiga]

Exactly, 400 is by no means the saturation point. Not for photosynthesis, not for leaves, not for entire cannabis plants.

I've posted this already in the other thread. It's a chart of the results of 175 grows from the YOR website. The red line is a smoothed average:
View attachment 3789263

Clearly lights well up and over 1000umol/s/m2 will work just fine.

Most datapoints from 6-800 I see. With all the spread in yield that the whole spectrum of intensities. What does the color codes mean?

 

[PhotonFUD]

"an accredited university which happens to show a chart where the photosynthetic rate increase peaks ~400 umoles."

The "rate of increase" of the photosynthetic response goes up with lower PPFD but I'm not sure if there's a minimum where that doesn't hold true. The "photosynthetic response" goes up with higher PPFD, flatlining around 1500, though there's some ambiguity about how the curve is affected indoors. It certainly doesn't max out at 400 though. Anyone who has grown with near 400 and much higher knows this is true.

Key word is rate. Other one is peak. The rate of increase peak basically means anything after that point will be less efficient. Not trying to be condescending as some have accused me of, but it would be better explained reading up on calculus.

You can improve efficiency by moving some light to areas of the plant where that energy will provide more of an increase. Light intensity increases beyond 600 PPFD provide less benefit than the same increase would be to leaf surface exposed at less than 400 PPFD.

Also consider that plants have evolved to grow best in uniform light. As you point out, there is some ambiguity as to the effects from various factors introduced with indoor growing under artificial light. Ever consider that the plant is stressed from such an imbalance?

 

[wietefras]

Most datapoints from 6-800 I see. With all the spread in yield that the whole spectrum of intensities. What does the color codes mean?

Green is with CO2 enrichment and blue is without added CO2.

 

[PhotonFUD]

Will you double the yield by doubling the light? Perhaps to a point, and that would be the point of highest light efficiency. But you'd still get more by increasing, for a long time. Cost/g would increase, from very fucking low to just fucking low. Cost from electricity, obviously, most other factors would have less impact, like infrastructure which doesn't change.
I can live with diminishing returns for a long time as long as the returns keep on being good. I want to cramp in as many photons as possible without harming the girls. I definitely don't want to give them DLIs of 17 like the 400ppfd. 17 is pretty good for lettuce. 800 is 34.5ish, so a lot better. 1000+ is unknown country for me yet but not for long.

DLI has area as a factor. If you are hitting the top 20% of the plant with an average of 800 PPFD with the rest of the plant averaging only 50-100 PPFD, your plant is still only going to average 200-240 PPFD which is what you use to calculate DLI.

People are mistaken if they think DLI for the entire plant is based on the PPFD at canopy. Now chew on that for a bit.

 

[wietefras]

You can improve efficiency by moving some light to areas of the plant where that energy will provide more of an increase.

That's a completely different discussion.

We grow the plants out wide to provide a spread out canopy on top instead of the more Christmas tree like shape that Cannabis plants grow into naturally.

This has nothing to do with a ~400umol/s/mw saturation point.

There is no peak at 400umol anyway. The efficiency still goes up when you drop down to 200umol. It's pretty much a steady decline in efficiency from 0 to 1500.

DLI has area as a factor. If you are hitting the top 20% of the plant with an average of 800 PPFD with the rest of the plant averaging only 50-100 PPFD, your plant is still only going to average 200-240 PPFD which is what you use to calculate DLI.

People are mistaken if they think DLI for the entire plant is based on the PPFD at canopy. Now chew on that for a bit.

Oh come on man. You have got to be kidding me! Stop it with the nonsense already.

There is really only a tiny fraction of light which is not absorbed by the canopy if you have a filled grow area. All the light which is absorbed counts towards the DLI.

It's complete bullshit that you only end up with a quarter of the PPFD and therefore quarter of the DLI because a part of the plant is lit less.

That is not how any of this works. At all!

 

[PhotonFUD]

Even his changed interpretation makes no sense, since leaf tests have shown that single cannabis leaves can use even 1500umol/s/m2 just fine.

Besides he never made the claim before and simply said that we should aim for ~400umol PPFD with our lights.

Why don't you move on.

It is obvious you don't understand the basics. Even simple math is beyond you.

You have already admitted to being upset and have only contributed emotional responses that are not relevant to the discussion. Apparently so emotional that you are now fabricating things such as accusing me of changing my position when I have been steadfast. You should step away from your computer, go for a walk or something.

If you don't want to learn, that's fine. If you think you have the best way, that's fine. You have every right to remain ignorant and apply whatever you think works best for you.

 

[wietefras]

Lol, yeah sure. Keep spreading your "FUD" and we all will keep making fun of it.

Eagerly awaiting your 5g/w projected 400umol harvest though. It's going to be hilarious when you suddenly stop posting crap after you figure out that you really aren't getting much more g/W and ended up with about half the yield that you could have had.

 

[PhotonFUD]

Lol, yeah sure. Keep spreading your "FUD" and we all will keep making fun of it.

Eagerly awaiting your 5g/w projected 400umol harvest though. It's going to be hilarious when you suddenly stop posting crap after you figure out that you really aren't getting much more g/W and ended up with about half the yield that you could have had.

Does that mean you are going to stop posting in this thread? If so, great.

 

[HydoDan]

Mr Spock says do not get emotionally attached to your grow... give it half the light it needs and don't cry about your results... You don't have a clue!!