Photosynthesis Under Solid State Light. Setting the Standards .

frica

Well-Known Member
The decor series is great at causing common herbs to bolt. Could be good or bad depending on what you want.

For human vision for some odd reason I love the appearance of a 2700k, 97cri emitter, with a pair of 4000k 80 cri emitters on either side of it all. It adds a certain 'gleam' to glass ware that I find memorizing.
The Decor series/high CRI Crees have a very sexy light spectrum output.
Very high in the red and also a nice peak at blue.
 

coolbreez1

Well-Known Member
I was not meaning to imply that the high CRI unto its self would make it a better grow light, the CRI has nothing to do with my statement beyond indicating which light I was referring to. I was just looking at the fact that it has much more red in the higher end of the spectrum and more magenta, and that without doing any of the math it looks as if it would best match the PAR we are looking to replicate.
 

alesh

Well-Known Member
I'm pretty sure that a lot of you have seen this chart many times.
Fig Tik 3.jpg
Tikhomirov, et al., 1991
It's an interesting one, however, applies to 15-day-old radish canopies.

My question - is there a similar chart for cannabis and/or a plant more similar to cannabis than a radish? Such a chart would make it possible to determine maximum and most efficient point of intensity for each spectrum.
 

Abiqua

Well-Known Member
Why not? I'm interested in your logic here.
HPS is something like 22 CRi.....

Color rendering index is another "anthro" light source, how well a light renders to the human eye....but because of its classification, can be kind of broken down into segments and use to guesstimate [technically]....but not many mess around with it....

although those top bin CXB 3590's may change that in the future, since the output doesn't seem to be throttled in the 600-700nm as with other high CRI models, as based on some of the predictions from the guru's around here.....

The overall gist so far is that high CRI is really just a bottleneck for photon outpout [decreasing] and the trade off with "more" of the red and deep red frequency's available to achieve "high" Cri, but at a lower photo output trade-off ....again newer diode tech, may change that.....
 

ttystikk

Well-Known Member
HPS is something like 22 CRi.....

Color rendering index is another "anthro" light source, how well a light renders to the human eye....but because of its classification, can be kind of broken down into segments and use to guesstimate [technically]....but not many mess around with it....

although those top bin CXB 3590's may change that in the future, since the output doesn't seem to be throttled in the 600-700nm as with other high CRI models, as based on some of the predictions from the guru's around here.....

The overall gist so far is that high CRI is really just a bottleneck for photon outpout [decreasing] and the trade off with "more" of the red and deep red frequency's available to achieve "high" Cri, but at a lower photo output trade-off ....again newer diode tech, may change that.....
CRI= Color Rendering Index. Indexed against what? The sun. That's not 'rendered to a human eye'. You got it mixed up with lumens.

HPS CRI = 22, proof enough that if you give plants enough shit, they'll eat it. Good spectrum is no substitute for adequate irradiance, however. Turns out the ladies like both.
 

Abiqua

Well-Known Member
CRI= Color Rendering Index. Indexed against what? The sun. That's not 'rendered to a human eye'. You got it mixed up with lumens.

HPS CRI = 22, proof enough that if you give plants enough shit, they'll eat it. Good spectrum is no substitute for adequate irradiance, however. Turns out the ladies like both.
Again, its an an anthro light measurement....it measures how well light is reproduced according to a natural source [Sun]...that WE see...
 

ttystikk

Well-Known Member
Again, its an an anthro light measurement....it measures how well light is reproduced according to a natural source [Sun]...that WE see...
No, the index is measured as instruments see the Sun's mix of spectra and the index quantifies how well the artificial light source renders it. Human perception is not a part of CRI determination.

I'm not saying that a CRI of 100 is the be-all, end-all goal of lighting. What I AM comfortable saying is that the plants have evolved with the sun in place. Artificial lighting that does a good job of emulating this spectrum would at the very least be a great place to start.
 

Abiqua

Well-Known Member
Human perception is not a part of CRI determination.
.
“Color rendering” describes how an object appears to the human eye based upon an ideal or natural light ...

http://eu.mouser.com/applications/lighting-cri/


and your right in theory, a higher CRI would make us assume that might be the best light we can see [really bright mid day summer sunlight], that a plant would like....and an adjustment has been made to the original R9 to R14....so 14 spaces are tested individually to achieve CRI.....

but anthro vision is a weak tool for plant calibration...I want to see what the DNA does when it interacts with a photon indirectly...5 years maybe less....
 

Rahz

Well-Known Member
Is it the Sun or the Mcree curve we should be emulating?

I'm all for a broad white spectrum, but adjusting blue and orange up to meet the Sun's output? I don't see that as a great deal. It's possible LED, having enough blue and a spike in red at the top of the Mcree curve, is more ideal than the Sun.
 

PurpleBuz

Well-Known Member
[
Is it the Sun or the Mcree curve we should be emulating?

I'm all for a broad white spectrum, but adjusting blue and orange up to meet the Sun's output? I don't see that as a great deal. It's possible LED, having enough blue and a spike in red at the top of the Mcree curve, is more ideal than the Sun.
I think emulating the sun is the ultimate goal. BUT it costs a lot of $$ to emulate the sun. so figuring out where we focus the watts, to reduce the cost is the real challenge. Its easy to say I'll mix some 3K cobs with some 65K cobs, but it may be more efficient to supplement 3K cobs with some Royal Blues+UVA+Deep Red.
 

Rahz

Well-Known Member
That's a whole lot of green. If PPFD can only be so strong I question whether sunlight will produce the best growth. Plants did evolve under the Sun but that doesn't mean the Sun is the best.
 

Meinolf

Well-Known Member
That's a whole lot of green. If PPFD can only be so strong I question whether sunlight will produce the best growth. Plants did evolve under the Sun but that doesn't mean the Sun is the best.
The cheapest for that matter. But it may be true especially for generations of strains bred under bulbs.
 

PurpleBuz

Well-Known Member
That's a whole lot of green. If PPFD can only be so strong I question whether sunlight will produce the best growth. Plants did evolve under the Sun but that doesn't mean the Sun is the best.
Its been shown that
- green light penetrates deeper in the canopy than light based primarily on chlorophyll a & b peaks red/blue.
- is effective in driving photosynthesis
- avoids oversaturation and burning from high levels of red/blue monos. Plants can use a higher ppfd with a wide spectrum light, that includes green.
 

Rahz

Well-Known Member
I'm not knocking green light, just questioning whether sacrificing some blue and green from the suns spectrum for some extra red is a bad deal.

I think we're both theorizing, and that's cool. There actually is equipment out there that could be tuned to test these theories. More money than I have to play with though.
 

Scotch089

Well-Known Member
@stardustsailor

I'm rereading some things out of this thread to revamp myself, I noticed you recently posted something about leaving out monochromatic and siding with the light side, what has made you stance changer? I am still stuck in my day one beliefs (which you and others have agreed upon at one time, w+r fo life!) But am always open to hear why another option may be better suited.. the floor is yours sir!

Just curious what other tests/data may have been released in time

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