Led vs Cmh

[Yodaweed]

High CRI (2700-3500K) lights just tend to have more red (than similar Kelvin and 80 cri lights) and a peak close to 630nm.

That's why they're often preferred.

In the end it doesn't really matter that much.
Plants look nicer in high CRI light though, if you like to look at them.
Also easier to identify if something's wrong with your plant.

Yeah higher CRI is for human eyes, the higher CRI lights will be easier to view plants in. That has literally zero to do with how they grow though. My hps has a CRI of 22 , but i would wager it has more red light than a 90 CRI LED by a large margin. CRI is for humans to take pretty pictures in, not for plants to grow.

 

[nevergoodenuf]

I disagree, higher CRI means lower lumens and lower lux and even lower PAR #s. But my plants, like Dawgs, just are liking it more. My 3000k/90cri grew similar to the DE, while the 3500k/80cri lacks a bit, but still looks great, and the 4000k/70cri lacked in everyway. Less stretch, less leaves/branches, even though is should have been the most efficient. But even in 3000k, the light looks like a MH next to the DE HPS. There seems to be more than enough blue. I also, now prefer to veg under the 3000k/90cri over the 5000k.

 

[CobKits]

That has literally zero to do with how they grow though.

not in principle. HPS is near 20 and CMH is in the 90s

as far as phosphor based cobs/SMDs go, 90 cri will always offer more photosynthetic energy than 80 which also has more than 70.

lumen measurements are more centered to visible light, green centered, which is less usable by plants

 

[Yodaweed]

not in principle. HPS is near 20 and CMH is in the 90s

as far as phosphor based cobs/SMDs go, 90 cri will always offer more photosynthetic energy than 80 which also has more than 70.

lumen measurements are more centered to visible light, green centered, which is less usable by plants

true, that just has to do with how those lights are designed, not all lights are the same, CRI doesn't have to do with how plants grow, PAR does.

 

[frica]

There's also the 1750K Gen. 7 Décor Food Meat & Deli Vero 29 if you really like the red.

 

[CobKits]

true, that just has to do with how those lights are designed,

yup 100% an effect of the phosphor technology used in this case, we just got lucky that its a match, kinda like the people growing with streetlights for the last 40 years

 

[Yodaweed]

yup 100% an effect of the phosphor technology used in this case, we just got lucky that its a match, kinda like the people growing with streetlights for the last 40 years

i don't think streetlights and the current generation of hid lights are the same, DE HPS, digital ballasts, CMH , DE CMH , etc....lots of changes have happened and HID lights have evolved, just like LEDs have since they came out with little tiny 1w diodes. Now we got LES , COB , high powered mono's , reflectors , etc...lots of evolution's.

 

[CobKits]

well yes DEs are advanced and theres been no shortage of tweaking SE bulbs to get more blue into the spectrum. still plenty of people using off the shelf HPS and MH for decades successfully before hortilux etc became popular. same with cobs, were just starting to see horti-specific models but the off-the-shelf ones work fine

 

[Yodaweed]

well yes DEs are advanced and theres been no shortage of tweaking SE bulbs to get more blue into the spectrum. still plenty of people using off the shelf HPS and MH for decades successfully before hortilux etc became popular. same with cobs, were just starting to see horti-specific models but the off-the-shelf ones work fine

yea , the cobs ppl are using for growing canna aren't horti-specific , they are really designed as high bay LED's for warehouse lighting. I'd say the HID lights are more horti-specific than almost all LEDs, the only COB LED i know that is made for growing plants is that flip chip opto one.

 

[Dreddd]

true, that just has to do with how those lights are designed, not all lights are the same, CRI doesn't have to do with how plants grow, PAR does.

Explain The Dawg's grow then, the 90 CRI has slightly less PAR, he shows the measurements on page one, and yet the 90 CRI plants are much bigger and further into flowering then the 80 CRI ones, same nutes, same clones, just different CRI.

 

[Rahz]

Red photons are more likely to cause a photosynthetic reaction. Even with lower par a spectrum with more red can have a higher response frequency. Multiple tests have/are proving this out.

 

[Dreddd]

Red photons are more likely to cause a photosynthetic reaction. Even with lower par a spectrum with more red can have a higher response frequency. Multiple tests have/are proving this out.

Agree 100%.

 

[Yodaweed]

Explain The Dawg's grow then, the 90 CRI has slightly less PAR, he shows the measurements on page one, and yet the 90 CRI plants are much bigger and further into flowering then the 80 CRI ones, same nutes, same clones, just different CRI.

More red, has to do with how LEDs are made and the phosphor coating technology they use to try to imitate white light (no LED produces white light without phosphor coating or mixing colors). CRI is for human eyes to see the contrast of colors it doesn't effect plants.

 

[Greengenes707]

Let's put some numbers to this guys...express "less" numerically. Let's talk radiant efficiency. Then let's talk how that converts to photons(spd...r9 values...ect). And finally steady state real world operation. And then we may have a relatively solid base to make and assert these conclusions. Vague and unsupported explanations are not the way to describe and show what is actually going on or help support these small and few test.

So you guys are basing "less PAR" off one number from data sheet extrapolations and single current SPD's?...that repeatedly states flux numbers have a 7%(cree, bridgelux),10%(citi)+/- tolerance ...(as in could go both ways, 20% swing/range)...then definitively implying that the typical numbers stated, are the exact specs and not the range that will happen in real life conditions? With many system variables, further blurring the lines of what is happening.

But what about reality...
@The Dawg, who shows his actual canopy PPFD with his meter, not a data sheet. Being a mq200 meter, is skewed to show less for the 90 cri but canopy ppfd's are the same on each side..somewhat supporting more photons if we had to make a call based on the info. Photons being equal but disturbed over a more ideal SPD, and the results seem to show it.

And
@Rahz's meter test showing ~5% difference from 80cri to 90cri on his meter...but was a different meter than dawg. But also showed the 70cri performing really well and substantially better than 80 n that test, and somewhat within error of 90cri considering the test parameters. That is completely against a spectral benefit reasoning. And really offers no explanation without being repeated a few more times.

Here is my issue with the tools, not the comparison...
"This increased surface area of the Apogee MQ-500 PAR Sensor is supposed to read more of the light, especially in the blue end of the spectrum, which is quite important in our windex-blue, LED lit aquariums.We tested the Apogee MQ-200 and MQ-500 side by side under different channels of LED colored light of a Radion and found quite a significant difference in measurements. The MQ-200 read higher especially under UV, Blue and Royal Blue channels of the Radion XR30w Pro 3rd Gen, slightly higher under white and green light, and only under red light did the newer MQ-500 give a higher PAR measurement."
https://reefbuilders.com/2016/03/28/apogee-mq-500-par-meter-hands-on-and-first-impressions/

So let's look at some more real world data to muddy the waters more...

One angle based on steady state operation.

Anyway, CXB3590 3000K 80CRI vs 90CRI, minimum values, temp set to 25°C in PCT.
View attachment 3736007

Thanks @alesh for doign what you have always done...top notch info and practices what he preaches and tests.

and here is another angle(not so real world), based on only minimum pulsed measurements...


MHB-B...6.5% favoring 70cri


XPG3...9% favoring 70cri


XTE...9%...favoring 70cri.

 

[CobKits]

thanks for chiming in @Greengenes707

so moving forward, is it possible to generate a consensus on what spectrums are active and/or effective? or will that always be debated?

can we agree that the standard yardstick of PAR is inherently flawed as it:
-gives equal weight to wavelengths from 400-700
-expressly disregards activity of UV and IR wavelengths jsut above and below this? we know uv aids in trich expression, and emerson effect is a real concept which is totally disregarded by classic PAR measurement


also what are your thoughts on McCree/YPF? is that single leaf study inherently flawed based on modern day science? obviously we know from experience that 580-730 give the best return, and blue is necessary to a point (but inhibits above a certain point). Also it appears that for best vigor and full development, we do in fact need the intermediate actinic/green/yellow bands (commonly found in phosphor led spectra, and supplemented to mono-based led fixtures as "warm white".) but how much white do we need? at what point is it diminishing returns?

i know thats a bag of questions but it seems the more we ask the less we know

in the end it seems that many experienced growers who switch from 80 to 90 (and to a lesser extent 3500 to 3000k) seem to be happier with the results in bloom, despite the lower PAR numbers (on a PPF/W basis). so what equivalence can we consider between say a 3000k 90 and a 3500k 80? is 90% of the PAR required to achieve the same results. electrical input wise its the same in many cases.

sorry just rambling, i know that was all over the place. im escaping the winter of hell and about to find time to get serious with the sphere. i dont want to just generate data. i want to generate useful data that we can do something with, and these questions eat me up. im about to throw away the steeply filtered li-cor in favor of a broader photodiode to measure 300-800nm and maybe we can correct back to whatever we think the most appropriate definition of "PAR" is for our purposes. im pretty sure that the pro light labs who measure ppf are just sharply truncating those wider spectrum measurements to 400-700nm - 90 cri will lose every time in this case

 

[CobKits]

Explain The Dawg's grow then, the 90 CRI has slightly less PAR, he shows the measurements on page one, and yet the 90 CRI plants are much bigger and further into flowering then the 80 CRI ones, same nutes, same clones, just different CRI.

you guys are kind of saying the same thing

Yoda is just saying that its not just because its higher CRI does it have a good effect. for the way phosphor cobs produce light the higher CRI versions just happen to throw more photons on the most active photosynthetic spectra. its a coincidence. 20CRI HPS also hammers this same region but has poor CRI, again just a result of the way the arc-tube creates light

the good news is that almost all cobs have somewhat similar spectra. a 3000k 90 from bridgelux should be reasonably similar to a 3000k 90 from cree, and both should be somewhat different t from their 3000k 80cri counterparts, despite the fact that none of the 4 spectrums will really be the same, the ranges will be close so the behavior should be similar, at least similar enough to be within our limited range of understanding at this time

 

[The Dawg]

90 Cri



80 Cri

 

[The Dawg]

90 Cri Bud

80 Cri Bud

 

[The Dawg]

 

[1KTrees]

View attachment 3916600

So now par and ppf don't matter anymore? Now I have CRI envy