How do you know there is par loss? Can you show the data? I can only find information on their Luminous efficiency which is worthless of course 90 cri will have less lumens. And we should remember par meters do not measure anything outside 700 nm yet the 700nm - 730 region is crucial for the Emerson effect, I see alot of people adding far red too 80 cri cobs running them all day because they want to harness the Emerson effect, anyone who does this should just go with a high cri you wont have to sacrifice as much efficiency and you will target the Emerson region perfectly, 730 nm is just a bit to far, the Emerson effect isn't about targeting specific wavelengths anyways but rather having a broad spectrum from red to far red and no combination of leds can do this like a high cri. If you dont think the Emerson effect is important you should still remember that even though the orange light that dominates 80 cri leds yield the most photosynthesis per photon ( as shows the the mcree curve) it doesn't yield the most photosynthesis when weighted by energy. Shorter wavelengths like deep red put out more photons per joule then orange light. Which is why when it comes to mono-color leds deep red is by far the most photosyntheticaly efficient.. I'd really like to see some data comparing their radiant efficiency and photon flux,i do believe the red phosphors used may not be as efficient but its probably pretty close. Close enough for me to justify sacrificing some efficiency for a far superior spectrum
Can someone explain 80 CRI vs 90 CRI- LED
- Thread starter BullShark
- Start date
I should also add that high cri doesn't just have more red and deep reds it also has more green this is where the photon loss occurs, if you could drop the green phosphors and just have orange and red you would lower the cri and lumen output making horrible for illumination but greatly increase ppf higher then any cob without sacrificing anything in the red to far red region.
hillbill
Well-Known Member
Maybe.
nfhiggs
Well-Known Member
Emerson effect occurs at 670nm and 700nm. The thing to keep in mind about the Emerson Effect is that its really only effective at relatively low light levels. As light intensity increases, its effect drops off. IMO, if you are saturating the plant with PAR light in the range of 800-1000 PPFD, the Emerson Effect may not make a huge difference.
Rahz
Well-Known Member
That was a while back and I've since completed a grow test that contradicts the readings I took at the time.
Preliminary PAR test results (citi g5 spectrums)
3000K70CRI 950
3500K80CRI 921
3000K80CRI 905
3000K90CRI 856
2700K90CRI 780
When a conversion factor similar to YPF was applied results narrowed but the 3000/70 result was still at the top and the 2700/90 still at the bottom... however a grow test was done and both 90 CRI samples produced the best yield (3000/90 being the best).
For the latest Vero (g7) on paper there's very little difference in electrical efficiency between 80 and 90 CRI and the PPF is actually higher (3000/80 -vs- 3000/90) for the 90CRI spectrum. For instance, electrical efficiency for 3000/80 @ 700ma is 57%, 3000/90 is 56% (based on LER of 332 for 3000/80 and 280 for 3000/90). QER for 3000/80 is 4.68 and 3000/90 is 5.00. So we have both math and real world results now to suggest 90 CRI is the way to go.
70/80 CRI produces less vertical growth but the average tent and grow setup probably isn't going to necessitate using a low CRI.
SupraSPL
Well-Known Member
Good info @Rahz . 3 things working against 90 CRi in theory, having more of its energy spent in the green range, more energy spent outside of the PAR range above 700nm, and more losses converting blue photons to warmer white. But if manufacturers can somehow achieve a similar electrical efficiency, it becomes a lot more interesting.
For those who have invested in 80CRi have no worries, unless your COBs are very outdated switching from 80 to 90 CRi is not mandatory LOL
For those who have invested in 80CRi have no worries, unless your COBs are very outdated switching from 80 to 90 CRi is not mandatory LOL
Evil-Mobo
Well-Known Member
Randomblame
Well-Known Member
There's not only the emerson effect, we must not forget that under CRI90 significantly shorter flowering times are needed. (up to a week and more strain depending)
This may allow you to have one more run per year...
This may allow you to have one more run per year...
hillbill
Well-Known Member
Improvements on already highly efficient light sources will come in diminishing increments over time as the potential maximum is approached. My 80 cri veros in two lights do just as well as last year which was excellent. My 90 cri COBs do a little better, but not near enough for me to ditch already great COBs.
These smaller improvements come faster and faster so one must choose at which tech advance to invest in next
These smaller improvements come faster and faster so one must choose at which tech advance to invest in next
newguy123
Well-Known Member
During that grow test, Were the plants subject to the same light during the entire grow or only during flowering?
Photon Flinger
Well-Known Member
Vero SE 29 g7 c 3000k 80 and 90 CRI get the same par numbers within margin of error when run at the same wattage. Out of 24 cobs, they were all within +/- 5% (similar to your citizens) which is better than bridgelux's +/- 7% for luminous flux.
So it comes down to which grows better which was always the case.
So it comes down to which grows better which was always the case.
rshackleferd
Well-Known Member
BS aside Here is an actual test run
https://www.rollitup.org/t/one-more-run-with-the-cxbs-3000k-80-90-cri-qbs-are-next-in-line.938932/
https://www.rollitup.org/t/one-more-run-with-the-cxbs-3000k-80-90-cri-qbs-are-next-in-line.938932/
_eNVy_
Member
Well I'm sold on the 90cri. Correct me if I'm wrong, 90cri = more red with the disadvantages of slightly less efficiency and losing photons to green. 80cri = a bit more efficiency and a good balance with less loss to green? This would be for 3000k. I'm a noob with led cobs but I'm about to purchase (16) citizen CLU048 1212 3000k and was told to check this thread out since I originally wanted 80cri. Thanks
NoFucks2Give
Well-Known Member
Bullshit.
NoFucks2Give
Well-Known Member
I looked at the same Citizen CoB and got the 2700K 97CRI. It a matter of whether you want more green (lumens) or more red (PPFD).
Both the 3000K and 2700K have the same deep blue (near UVA blacklight) LED dies. The dies on each put out exactly the same amount of photons.
The difference between the two is the phosphor wavelength converter covering the deep blue dies. Just like how a black light illuminates the blacklight poster's phosphorescence, the LED's phosphor, converts the deep blue light to green or red phosphorescence.
You cannot be swayed by the Lumens. Lower CCT translates to less green and more red. A higher CRI translates to more red.
Lumens is a calculation from the LED's measured radiant flux (mWatts) or quantum flux (µMoles) and converted to luminous flux (lumens).
In the translation from actual radiated flux to luminous flux, the red is de-emphasized and the green grossly over emphasized.
Below are the CIE Photopic Luminous Efficacy conversion factors. For example Deep Red lumens must be multiplied by a factor of 15 when converting lumens to mWatts or µMoles. Lime Green (555nm) is multiplied by 1 because it is already
This table show the relationship between various LED colors
And this shows how colors of equal lumens are factored, and how lumens are leveled to the same playing field.
Rahz
Well-Known Member
Not bullshit. Orange isn't as effective as red in the Mcree study but it's no slouch either. 3000/70 has lots of orange so the enhanced spectrum of a 90 CRI sample wasn't enough to offset the large difference in the initial par readings. All it means is that YPF/Mcree isn't a perfect way of measuring spectrum efficacy for flowering.
NoFucks2Give
Well-Known Member
So you are saying a 3000K 70 CRI has higher PAR value than a 2700K 90CRI?
If so, that is incorrect.
I plotted the CIE xy chromaticity for citi 3000K and 2700K with an app I wrote today.
Not too much difference between the two, but 3000 has more green and less red than 2700. Difference in deep blue is negligible.
The bigger difference is in the CRI 90 vs. CRI 70 values and in particular the R9 value.
Notice below, the CRI 82 R9 is below 20.
What color is missing in the CRI 70?
NoFucks2Give
Well-Known Member
I'm very curious as to why you chose 3000 CRI 90 and I chose 2700 CRI 97.
Did I make a wrong choice?
What was your determining criteria behind your choice?