DHP Presents Citizen Cob 1812 3500k 80CRI Vs 1812 3500k 90 CRI

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JimmyJames905

Member
[QUOTE=" Apogee none and HF up to the 780nm..[/QUOTE]

Would this explain why my HF picks up 1400 μmoles on the 1750k (deep reds) but had difficulty accurately measuring blues? I got a very low PAR reading on a Cree 6500k. It was bright as hell but only registered 1700μmoles on the HydroFarm.
 
P

Photon Flinger

Well-Known Member
Greengenes707 said:
It is extrapolated...calculated...put to an algorithm///whatever you want to call it. But it is true...there is not "1200µmols" falling on the sensor when it reads 1200µmols. The sensor is ~1sqin...a square-meter is 1550sqin. The quantum meter reads out a figure for a m2...not the measurement of the single sqin.
The 1200µmols is extapotated out under the assumption of constant illumination equivalent to what the sensors experiencing for a whole m2(aka the other 1549sqin not measured).
Click to expand...

Sigh....it is called conversion and it is done when you what to represent something in another unit of measurement.

There is approximately (within some margin of error) the measured density of photons detected by the sensor. It is more than acceptable in horticultural applications and the less expensive units are good enough for hobby use. If you want to find the average density in your grow area, take measurements at different points to calculate. The more points the better but it is still more important to adjust to maximize leaf exposure.
 
P

Photon Flinger

Well-Known Member
JimmyJames905 said:
[QUOTE=" Apogee none and HF up to the 780nm..
Click to expand...
Would this explain why my HF picks up 1400 μmoles on the 1750k (deep reds) but had difficulty accurately measuring blues? I got a very low PAR reading on a Cree 6500k. It was bright as hell but only registered 1700μmoles on the HydroFarm.[/QUOTE]


PPFD is counting photons, not measuring the energy they are carrying. Shorter wavelengths carry more energy than longer ones. Bright as hell is a subjective term, you will need to be more specific as 1700umoles might be a great number at 24" but be not so great at if at 1".

When it comes to PAR, disregard the colors as you want to know how many photons are hitting. All photons work, the plant will adjust.
 
J

JimmyJames905

Member
Photon Flinger said:
Would this explain why my HF picks up 1400 μmoles on the 1750k (deep reds) but had difficulty accurately measuring blues? I got a very low PAR reading on a Cree 6500k. It was bright as hell but only registered 1700μmoles on the HydroFarm.
Click to expand...

PPFD is counting photons, not measuring the energy they are carrying. Shorter wavelengths carry more energy than longer ones. Bright as hell is a subjective term, you will need to be more specific as 1700umoles might be a great number at 24" but be not so great at if at 1".

When it comes to PAR, disregard the colors as you want to know how many photons are hitting. All photons work, the plant will adjust.[/QUOTE]
It was 1700 at 12". Not good. The Cree 5000k got twice that. I made a vid on it.
I was curious if the HF was poor army detecting blue led. When I had it tested at Guelph University (Canada's premier horticultural univ) the tech (a grad student) said it "didn't do so well" in the blues.
 
GroErr

GroErr

Well-Known Member
You know, there are probably threads already open for the level of detail you guys are discussing. Instead of hijacking this thread with a lot of white noise you could create your own thread and argue over there.

I'm pretty sure 99% of the folks watching this thread don't give a rats ass about your photon or par meter discussions. Just sayin...
 
CobKits

CobKits

Well-Known Member
Greengenes707 said:
They are normalized to one. Meaning whatever the highest output point is for each curve is...gets set to 1. This skews the representation of absolute/total output(not ratios) of bands. 4k has as much total red output as 3K...but more blue so by ratio it comes in as cooler. But is not less red as many think. Your plants are getting the same amount of absolute/total red.
Click to expand...
this seems counter-intuitive. yes i understand the graphs are relative but i would think its unlikely that a chip with less phosphor would still produce an equal gross amount of red spectrum as a chip with heavier phosphor. there has to be *some* equivalency of blue photons used to create red photons
 
P

Photon Flinger

Well-Known Member
CobKits said:
this seems counter-intuitive. yes i understand the graphs are relative but i would think its unlikely that a chip with less phosphor would still produce an equal gross amount of red spectrum as a chip with heavier phosphor. there has to be *some* equivalency of blue photons used to create red photons
Click to expand...
Well it is because he is incorrect. It is actually the phosphor layer that emits the photons in the light produced with a small amount of the original wavelength passing through as leakage.

That initial photon pump is used as an energy source to drive the phosphor layer. There isn't a 1 to 1 photon conversion as that doesn't happen. Photons are absorbed by the phosphor exciting electrons that move to a higher state that then release photons and move back to a lower state. The creation and destruction (if you could use these terms) of photons happens at a sub atomic level hence the quantum reference.

Electricity going to the LED is converted to both light and heat. The good 'heat' is from light that is absorbed and converted to heat whereas bad heat is the waste heat you need to manage with conduction from the source itself.
 
Greengenes707

Greengenes707

Well-Known Member
CobKits said:
this seems counter-intuitive. yes i understand the graphs are relative but i would think its unlikely that a chip with less phosphor would still produce an equal gross amount of red spectrum as a chip with heavier phosphor. there has to be *some* equivalency of blue photons used to create red photons
Click to expand...
We are talking broad band phosphor white SPD's...
VERO High CRI loss.jpg vero18-diff3K.jpg
2015-02-19 05.22.51.jpg

cxa3070chart.jpg

It's not simply less of the same phosphor mix to yield different cct's. The losses varies by mix.

Sorry @The Dawg...I'm done. Garden is looking good as usual. I've just been watching and enjoying till all this shit slinging started. My apologies.
 
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Metacanna

Metacanna

Well-Known Member
Greengenes707 said:
We are talking broad band phosphor white SPD's...
Click to expand...
Is the first graph representative of absolute output? If so, I suppose the testing was done with the same current across all chips.
If my understanding is correct, at first glance the 5000K seems the most efficient.

The 3rd graph shows relative intensity. What exactly is that?

Sorry if I'm slowing down your logic but I'm not PhD in Quantum Physics, just a regular guy how grows weed :eyesmoke:.
 
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thetr33man

thetr33man

Well-Known Member
Looking at all those dead fan leaves, I hate to think how much light is being wasted hitting those that could be penetrating further into the canopy!
 
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