PAR Readings
- Thread starter hiepatitis
- Start date
Gomer
Guest
So I am looking into this more so that I know the strict definition and came across this:
What I gather from that, is that it is pointless to try and equate PAR/PPF/PPFD to the growing potential of a bulb since photosynthetic efficiency is anything but a "any photon between 400-700nm is equally good" Strangely, the almost the entire reef community is taking Sanjay's numbers as the gospel guide to plant growth. The error isn't in Sanjay's data, but rather how people are using his numbers.
What I gather from that, is that it is pointless to try and equate PAR/PPF/PPFD to the growing potential of a bulb since photosynthetic efficiency is anything but a "any photon between 400-700nm is equally good" Strangely, the almost the entire reef community is taking Sanjay's numbers as the gospel guide to plant growth. The error isn't in Sanjay's data, but rather how people are using his numbers.
sfsuphysics
Supporting Member
[quote author=Gomer link=topic=3963.msg47321#msg47321 date=1214499917]
I'm confused. Why would there be 2 results depending on what calibration source you use?
[/quote]
I think because it's basically a solar cell, gallium arsinide(?) maybe, multilayered, and it detects whatever current/voltage the thing puts out, each layer is a various part of the spectrum As a result bluer and purple photos while they will register as energy, they get lost to their full potential.
I'm confused. Why would there be 2 results depending on what calibration source you use?
[/quote]
I think because it's basically a solar cell, gallium arsinide(?) maybe, multilayered, and it detects whatever current/voltage the thing puts out, each layer is a various part of the spectrum As a result bluer and purple photos while they will register as energy, they get lost to their full potential.
hiepatitis
Guest
The actual response and the plant response are not too far off for a good approximation. The defined quatum response on the other hand has higher discrepencies.
It's not a perfect measurement tool but it sure beats a lux meter. Even if it does not give an accurate reading, I think it is a good reference for comparing two lighting systems or the aging of bulbs etc. It's like a Hanna Phosphate colorimeter. Most people know that the specs say that it is inaccurate at the lower range but as long as it is consistent you can tell when your phosphate levels are getting higher or you can compare your levels to a buddies tank.
Anyone have PAR readings to compare with mine yet?
It's not a perfect measurement tool but it sure beats a lux meter. Even if it does not give an accurate reading, I think it is a good reference for comparing two lighting systems or the aging of bulbs etc. It's like a Hanna Phosphate colorimeter. Most people know that the specs say that it is inaccurate at the lower range but as long as it is consistent you can tell when your phosphate levels are getting higher or you can compare your levels to a buddies tank.
Anyone have PAR readings to compare with mine yet?
sfsuphysics
Supporting Member
See that spectral response is something that concerns me though. While yes I'll agree comparing bulbs is fine, and it'd rock for measuring how a bulb dims over time when our eyes tend to lie to us (ok maybe it's our memory). But one thing I've always wanted to check is the light levels in my greenhouse/porch, as I had a frag tank back there for a while (too much algae hade to yank it off line), and I'd be curious about how much light actually gets in.
Although the post Jeremy made kind of worries me, maybe I can put blue cellophane over the tank and get the same result
Although the post Jeremy made kind of worries me, maybe I can put blue cellophane over the tank and get the same result
Gomer
Guest
[quote author=sfsuphysics link=topic=3963.msg47379#msg47379 date=1214520669]
Although the post Jeremy made kind of worries me, maybe I can put blue cellophane over the tank and get the same result
[/quote]
If you weren't a physics guy, I would lecture you while I beat you over the head. Instead, I'll just beat you over the head.
Although the post Jeremy made kind of worries me, maybe I can put blue cellophane over the tank and get the same result
[/quote]
If you weren't a physics guy, I would lecture you while I beat you over the head. Instead, I'll just beat you over the head.
tuberider
Guest
[quote author=Gomer link=topic=3963.msg47391#msg47391 date=1214527064]
[quote author=sfsuphysics link=topic=3963.msg47379#msg47379 date=1214520669]
Although the post Jeremy made kind of worries me, maybe I can put blue cellophane over the tank and get the same result
[/quote]
If you weren't a physics guy, I would lecture you while I beat you over the head. Instead, I'll just beat you over the head.
[/quote]I'm not a physics guy, but I can incite violence, now I feel masculine!!
[quote author=sfsuphysics link=topic=3963.msg47379#msg47379 date=1214520669]
Although the post Jeremy made kind of worries me, maybe I can put blue cellophane over the tank and get the same result
[/quote]
If you weren't a physics guy, I would lecture you while I beat you over the head. Instead, I'll just beat you over the head.
[/quote]I'm not a physics guy, but I can incite violence, now I feel masculine!!
sfsuphysics
Supporting Member
Is Tony trying to imply blue cellophane won't let blue light through?
hiepatitis
Guest
It took mine a while to come in. They don't have them in stock so they had to make mine per order. I'm interested in seeing T5 vs MH
sfsuphysics
Supporting Member
[quote author=hiepatitis link=topic=3963.msg47408#msg47408 date=1214539763]
I'm interested in seeing T5 vs MH
[/quote]
I'd be interested in how you're going to really compare them though, seems like an apples and oranges comparison. If you stay close to the bulb or directly under the MH most likely will dominate because most of it's light hits the sensor, if you go off the center the T5s most likely will be brighter simply because the bulb stretches across the tank.
I'm interested in seeing T5 vs MH
[/quote]
I'd be interested in how you're going to really compare them though, seems like an apples and oranges comparison. If you stay close to the bulb or directly under the MH most likely will dominate because most of it's light hits the sensor, if you go off the center the T5s most likely will be brighter simply because the bulb stretches across the tank.
hiepatitis
Guest
A grid with values at that particular point. It's a given that halides don't have even light spread but a rid can show the overall picture.
G
GreshamH
Guest
[quote author=hiepatitis link=topic=3963.msg47408#msg47408 date=1214539763]
It took mine a while to come in. They don't have them in stock so they had to make mine per order. I'm interested in seeing T5 vs MH
[/quote]
From my experience with them, they stock very little. When I ordered my second unit it took a couple weeks as they had clouds every day and they actually calibrate using the sun
It took mine a while to come in. They don't have them in stock so they had to make mine per order. I'm interested in seeing T5 vs MH
[/quote]
From my experience with them, they stock very little. When I ordered my second unit it took a couple weeks as they had clouds every day and they actually calibrate using the sun