Cannabis absorptance spectra: calculated and compared

[Beta Test Team]

We're happy people find these topics interesting.

Ha, ShaggyBalls (btw, why did choose that username?), yea, PUR isn't what we want to use, we want to use YPF, or our new YPFc. PUR is what knna called the value he created using the work of Inada (i.e. multiplying the Inada curve by lamp energy by nm). We aren't using Inadna's work on photosynthetic curve, only McCree's, because Inada didn't use quantum units of measurement so it can't be weighted with absorptance (which is why Inada's work was less favored than McCree's, even to today).

Originally knna weighted Inada's curve with Cannabis absorptance, but that's not correct, so he subsequently changed the calculation to remove absorptance (in his most recent spreadsheet ca. 2009). Here are some of knna's thoughts on this subject:
https://www.icmag.com/ic/showthread.php?t=138742

 

[shaggyballs]

We're happy people find these topics interesting.

Ha, ShaggyBalls (btw, why did choose that username?),

First, I don't like clogging your thread...but.
You asked, and all are wondering, so I figured I would go public.

I go buy the nickname Shaggy a lot, it way given to me...your not allowed to make up your own nickname, ya know.

But there is 1000000000000000000000 shaggys in the world.....right, never get that screen name it was always taken.
I have a horrible memory, so I needed something easy to remember.
I was once a pro Paintball Player (ESPN) flyin' to other countries.
Full sponsorship, everything paid for.....so I was known as a Baller!
So you could say "shaggy balls" you would think you would not have to fight for a name like that right..Nope, not true there are others as foolish as I....LOL
I wanted my wife to be "Fuzzy Beaver" but she was not havin' it!
shag

 

[Beta Test Team]

Asked and answered. (Not like I can talk, our username is a bit odd, as well.)

Your reasoning makes sense, and it sure is memorable!

 

[staank]

soo.. plants use light.. who knew.




seriously though,
thanks for sharing all your work.

 

[Meison]

I'll be following your thread

For those interested I'm going to write a thread tomorrow with the updated (corrected) graphed RQEs of Cannabis of photosynthesis (growth chamber and field conditions). And also upload some other graphed RQEs of Cannabis, like phototropin response and stomatal opening and stomatal closing.

That thread is found here:
https://www.icmag.com/ic/showthread.php?t=298468

edit: Any chance you would test the Gavita LEP 300 41.02?? I would love to see those results

Enjoy the reading

"Green light drives leaf photosynthesis more efficiently than red light in strong white light. Revisiting the enigmatic question of why leafs are green"

http://pcp.oxfordjournals.org/content/50/4/684.full.pdf+html

This is why

 

[Dion]

wow...this thread is way to smart.... i was hoping to find a chart showing which wavelenths plants need most, like as in if you were to build an led array what percent of diodes would be which nm for optimum results but i cant understand any of the graphs

you guys are obviously not stoners, weed makes you dumb and lazy lol

 

[Beta Test Team]

I think maybe you're looking at it the wrong way. I think this is the fault of LED companies, that have for too long propagated the idea that there is an "ideal spectrum." As well as the flawed idea that chlorophyll absorbance shows the ideal spectrum (i.e. peaks in blue and red).

See the first post in this thread, that shows how Cannabis absorbs different wavelengths. This shows that the often cited claim that green light isn't used is totally wrong, and sadly, that's a claim many LED makers like to tout.

To see approximate effects from various wavelengths, check out the graphs in this thread:
https://www.icmag.com/ic/showthread.php?p=6718314

It's best to provide white light (below 400 nm to above 700 nm, up to about 750 nm) for Cannabis growth, not specific wavebands like only blue and red.

 

[Ranger]

deleted

 

[Beta Test Team]

For the first question, I don't think it's accurate enough to guess the conversion factor from the old literature. I think it's much better to calculate it for your lamp.

Here's one way to do so, this is just a rough guide to give you an idea of the steps. What you would do is digitize your lamp's SPD from 390-830 nm (optionally as relative values out of 100%). Then convert the values from 400-700 nm per nm to spectral wattage (W per nm) and then convert W/nm to umol/s/nm, and integrate the values for find the umol/s in PAR range ('radiant PPF') for the lamp (this is the value provided by some manufactures from an integrating sphere). Then convert W/nm (from 390-830 nm; or as wide nm as the SPD shows) to spectral lumen (lumen per nm) with the luminous efficiency functions (CIE values from 2006; 'photopic curve') and integrate them (add all nm values) to find the lumens of the lamp. Finally, divide the radiant PPF value by the lumen value to get your lux to PPF conversion (multiplication) factor you would use with your lux meter to find PPF.

The links below, a web page of Dr. Ivo Busko and a study, are where you can find much more technical/mathematical info. Both of those resources are what we're using to create much of HISSA (as well as adding some of our own touches), and we're also using knna's work as well, which was based strongly on Dr. Ivo Busko's work found in the first link (Dr. Busko is a Ph.D astrophysicist). Using both of those resources some really useful and interesting data can be calculated:
http://www.discusnews.com/article/cat-04/lightcompare.shtml#S-3
https://mega.co.nz/#!m40HFQbB!wtujIooa14CZOUy7RS2inQBX2lQU2-qgoSmsyr9dwXM

However, if you'd prefer, I could do that for you using HISSA as it's fully functional and would take me much less time as lots of things are automated with HISSA.

To find the actual PPF (or, PPFD) and DLI yes, you need to take many measurements in a 3'x3' area, convert all lux values to umol/s/area2 values, and then find the umol/s/area2 average which is PPF (umol/s/m2). However, for indoor growing a more important set of variables I think are umol/s/ft2 in PAR range, mean of all umol/s/ft2 values over the whole canopy, and the min/max values or min % of max (min/max*100) of the former and latter.

I think measuring lux every 4" to 6" (or 12") squared would be sufficient for canopies with good uniformity, to find PPF.

It's important to note PPF (and lux) assumes very high irradiance uniformity (like from the sun), so outside you can just take one measurement and that's the PPF (because all umol/s/area2 values within a 3'x3' are the same). That's also why you would need to take many measurements indoors, due to reduced irradiance uniformity under electrical lighting.

 

[Ranger]

deleted

 

[Beta Test Team]

Those values you got from knna's spreadsheet don't look correct. And using 5 nm stepsize is going to introduce considerable errors, it's better to use 1 nm stepsize, or 2 nm.

I'm not sure what you mean by this: "I input my numbers as graph numbers 1-10 being 1=10% 5=50% 10=100% I hope that's correct." But, that doesn't sound correct. You're supposed to input the Y axis pixel coordinate per each X axis nm (or per 2 nm), not a % for the Y axis values per X axis nm stepsize.

HISSA has a full tutorial, and lots of automation, but it's not publicly available yet. However, if you used knna's spreadsheet as I described above you would get the values you need, umol/s in PAR (what knna called "PPF" even though that's not correct) and lumen. Once you have those corrected values divide the umol/s in PAR by the lumens, to get your conversion factor.

Over at the site where knna's most current spreadsheet can be found (ca. 2009) he provides directions with screenshots for using his tool. Note however, the "PUR" and other weighted value ("PYF") are incorrect due to calculation error in knna's spreadsheet; also "PYF" is supposed to be "YPF."

 

[Beta Test Team]

What would be cool is some type of tutorial for people (idiots) like me.

You're definitely not an idiot, nor are most people that have trouble using knna's spreadsheet and understanding what I wrote. These topics are very complex and confusing (with all the different terms that mean the same thing, and also are misused), and the math is complex, as well. Even for scientists these topics are confounding at first - there's a very steep learning curve to understanding the whys and hows of the math and concepts underlying knna's spreadsheet and HISSA.

 

[Beta Test Team]

Oh yea, Ranger, I just looked at knna's most recent spreadsheet and he included the value you want. He called it "PPF/Klm." And in his context that refers to the ratio of umol/s in PAR range to lumen, but it's also the same thing as the PPF/Klux ratio I was writing about (and you're asking about).

In the context you're interested in, a conversion factor to convert lux to PPF, that's the same value. Although I should have written kilolux also now I think about it, that's the better way than PPF/lux.

And when I write PPF it means the same thing as PPFD, because they are synonyms. When knna's writes PPF what he really means is radiant energy as umol/s in PAR range, which is often mistermed "PPF," when 'radiant PPF' is a correct term.

 

[Ranger]

deleted -

 

[Ranger]

deleted

 

[Beta Test Team]

Ranger, if you wouldn't mind, please start a new thread for this topic and I'll post.

I'll ask a mod to move these posts to the new thread. The reason I'm asking is this discussion is pretty off-topic for the thread, and if it had its own thread more people can find it and follow along.

The way you're using knna's spreadsheet is wrong, you first need to scale the SPD so each X axis pixel = 1 nm along the SPD. Then you can digitize your SPD, which means finding the Y axis pixel coordinate for each nm along the SPD, and inputting the Y axis data into the spreadsheet.

Knna does a pretty good job with the directions, although, I find using GIMP (free) or Photoshop (not free) is much, much better than using MSPaint.

To get knna's most recent version (from 8-27-2008) Google this and read the thread:
"Bulb Analyzer Tool (actualized)"

Also, Google this and tread the tread as well, in case you haven't done so yet:
"Bulbs comparison tool"

 

[Ranger]

Sounds good on the new thread BTT, I have to run out for a while but I'll look into it later today. Again man Thanks for all the help!

Edit- I deleted some posts in order to maintain thread integrity, which the content of can be found in this thread

https://www.icmag.com/ic/showthread.php?t=303009

 

[butler]

I just want to say a massive THANK YOU to BTT for sharing this information.

 

[svrn]

thanks for sharing your findings BTT

 

[Kipod]

I came across this thread and i was completely stunned by the amount of useful data!
BTT, Thank you so much for sharing all of your studies!
Kip.