The Ideal spectrum.

Rahz

Rahz

Well-Known Member
Here's another graph of the Mcree curve. Not scientific but rather food for thought. If we mirror the outer curves we end up with two bell curves. The intersection explains the linear path between 475 and 540nm as it's the cumulative effect of both the red and blue curves. The bell curves do not explain the 660-680 hump.

If we assume the tops of the bell curves represent peak efficiency of cumulative photosynthetic and accessory pigments, then we only need three bands; 440, 610 and 675nm. I don't think LED is available in those exact wavelengths, but we do have 450, 630 and 660. Cree diodes are available in red-orange which is closer to 610 than the 630nm emitters. The difference in efficacy between 610 and 630 seems negligible so the suggestion might be to use whichever has the best radiometric efficiency. Chlorophyll A response seems to start tanking pretty bad at 660, so if there was a need for a new diode it might be one in the 670-675nm range to compliment the 610-630 band.

red-bluemcree.jpg
 
Last edited:
whytewidow

whytewidow

Well-Known Member
Old school grower said:
So true. But maybe I'm just putting too much thought into it. In the search for the best light "recipe". Always looking to improve or just bored and addicted to playing/building lights. Lol
Click to expand...
That's my problem. I went from being addicted to growing. To being addicted to building lights. And the DIY light building is way more expensive than growing. Atleast in my case. I just built two lights. Within the last 5 months. I've already rebuilt one. It had sammy strips and cobs. I removed the cobs and replaced them with H inFlux_L06 strips. And I have another 19 strip light I'm tearing apart changing out the heat sinks and adding 3 more strips for a total of 22. On just a tad smaller frame for ease of use. Other than adding strips. Theres absolutely no reason to rebuild it. It already flowers amazingly. She putting out average 6.2 zips per 2gal pots. But I'd like to hit 7 zips per 2gals.
 
Rocket Soul

Rocket Soul

Well-Known Member
Rahz said:
Here's another graph of the Mcree curve. Not scientific but rather food for thought. If we mirror the outer curves we end up with two bell curves. The intersection explains the linear path between 475 and 540nm as it's the cumulative effect of both the red and blue curves. The bell curves do not explain the 660-680 hump.

If we assume the tops of the bell curves represent peak efficiency of cumulative photosynthetic and accessory pigments, then we only need three bands; 440, 610 and 670nm. I don't think LED is available in those exact wavelengths, but we do have 450, 630 and 660. Cree diodes are available in red-orange which is closer to 610 than the 630nm emitters. The difference in efficacy between 610 and 630 seems negligible so the suggestion might be to use whichever has the best radiometric efficiency. Chlorophyll A response seems to start tanking pretty bad at 660, so if there was a need for a new diode it might be one in the 670-675nm range to compliment the 610-630 band.

View attachment 4255610
Click to expand...
Have you considered phosphored deep-red?
This from cutter:
https://www.cutter.com.au/product/ncsre17a/
 

Attachments

Rahz

Rahz

Well-Known Member
That must be what was mentioned earlier in the thread, curve is similar to monochrome but with a wider response. It would hit the 675 region just fine. Whether the cost in photons at other wavelengths is worth the phosphor solution I don't know, but the addition of +700 would be appealing for many.
 
Old school grower

Old school grower

Active Member
whytewidow said:
That's my problem. I went from being addicted to growing. To being addicted to building lights. And the DIY light building is way more expensive than growing. Atleast in my case. I just built two lights. Within the last 5 months. I've already rebuilt one. It had sammy strips and cobs. I removed the cobs and replaced them with H inFlux_L06 strips. And I have another 19 strip light I'm tearing apart changing out the heat sinks and adding 3 more strips for a total of 22. On just a tad smaller frame for ease of use. Other than adding strips. Theres absolutely no reason to rebuild it. It already flowers amazingly. She putting out average 6.2 zips per 2gal pots. But I'd like to hit 7 zips per 2gals.
Click to expand...
Everyone wants to improve their harvest one way or another. Quality or Quality. Lol
 
S

sethimus

Well-Known Member
Rahz said:
Here's another graph of the Mcree curve. Not scientific but rather food for thought. If we mirror the outer curves we end up with two bell curves. The intersection explains the linear path between 475 and 540nm as it's the cumulative effect of both the red and blue curves. The bell curves do not explain the 660-680 hump.

If we assume the tops of the bell curves represent peak efficiency of cumulative photosynthetic and accessory pigments, then we only need three bands; 440, 610 and 675nm. I don't think LED is available in those exact wavelengths, but we do have 450, 630 and 660. Cree diodes are available in red-orange which is closer to 610 than the 630nm emitters. The difference in efficacy between 610 and 630 seems negligible so the suggestion might be to use whichever has the best radiometric efficiency. Chlorophyll A response seems to start tanking pretty bad at 660, so if there was a need for a new diode it might be one in the 670-675nm range to compliment the 610-630 band.

View attachment 4255610
Click to expand...
which mono led has a spectrum like a bell curve? don't they usually come with a much steeper curve with a rather pointed tip?
 
Rocket Soul

Rocket Soul

Well-Known Member
sethimus said:
which mono led has a spectrum like a bell curve? don't they usually come with a much steeper curve with a rather pointed tip?
Click to expand...
Phosphored leds. White leds are a blue led with a phosphor coating, giving you the typical bell curve.

Rocket Soul said:
Have you considered phosphored deep-red?
This from cutter:
https://www.cutter.com.au/product/ncsre17a/
Click to expand...
^^this is a phosphor led with its peak around deepred 660nm. Fairly sure its based on a red led.

And if you check out citizens HPS replacement leds (2000k) its basicly the standard 80cri red bump (peak around 600nm) but without any blue. I think cobkits might have a few in stock still.
Edit: corrected peak nr
 
Last edited:
Rahz

Rahz

Well-Known Member
The 20B and 25E spectrum would be good with added 660 and 450. Whether it would be more efficient than 30E + 660 I don't know. For a single phosphor solution 30G (3000K 90CRI) might be as good as it gets. My experience between 3000K 70, 80 and 90CRI is that 70 produces more vegetative growth. They all yield about the same weight. 90CRI looked tighter and more dank, also finished a few days before the others.
 
Old school grower

Old school grower

Active Member
Rahz said:
The 20B and 25E spectrum would be good with added 660 and 450. Whether it would be more efficient than 30E + 660 I don't know. For a single phosphor solution 30G (3000K 90CRI) might be as good as it gets. My experience between 3000K 70, 80 and 90CRI is that 70 produces more vegetative growth. They all yield about the same weight. 90CRI looked tighter and more dank, also finished a few days before the others.
Click to expand...
What's your opinion on the Cxm22 3000k@90CriScreenshot_2018-12-29-13-40-28.png
 
Rahz

Rahz

Well-Known Member
It looks good. I haven't digitized the various 3000K 90CRI spectrums, but they all seem pretty similar. I don't think there's generally going to be a substantial difference from one brand to another.
 
You must log in or register to reply here.
Top