Par or ppf

Yeah, so what that is saying is that ppfd is a measurement of light.

Par is a the portion of that light that is useable by plants and corals for energy.

Then the article makes everything complicated and ivory towery by given a description of the units and formulas and letting us know that it cam be measured using several other standards ie metric vs imperial.
 
I had thought I had all of that grasped in my mind and then the ppf reference came about. Do you know if ppf and ppfd are the same?
 
PPF= Photosynthetic Photon Flux

PPFD= Photosynthetic Photon Flux Density

PPF will give you the number of moles (a way to measure the amount of photons; or light "particles") emitted per square meter.

PPFD will give you the the number of moles emitted per square meter per second. PPFD is a better measure of light intensity since it incorporates the amount of light emitted in a certain space in a certain amount of time.

From a quick Google search, it seems that you can't really convert between PAR and PPF/PPFD since it depends on the type and make of bulb that you're using.

FWIW: most of the sites I hit on this topic are geared towards more, ahem, "unconventional" uses of high powered lighting than reefkeeping. :bum::bum:
 
To measure a bulbs usefulness for growing plants in terms of energy output in photons you want to know the bulbs "Photosynthetic Photon Flux" (PPF) or more specifically the "Photosynthetic Photon Flux Density" (PPFD). The PPF tells you how many moles (method of measurement of photons) are being emitted per sq meter and the PPFD tells you how many moles are being emitted per sq meter and per second. PPFD is the best as it not only tells you what nanometers are emitted but how many moles are emitted in a given space and time which translates into the 'strength' of the bulb as more photons = more growth...PPF and PPFD measure the two rages of 400-500nm and 600-700nm.
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So, funny thing, I found that on a cannabis cultivation website.

Anyways, it is saying they are basically the same thing. Just that ppf is at an instant and ppfd is over time (1 second?). I'm not sure but I think you can use them interchangably for our purposes.
 
If the units are the same, they are the same measurement. The unit micromole is a pretty funny unit. micro is 1/1,000,000 and a mole is 6x10^23. It's like saying jumbo shrimp...

PAR just means a range of wavelengths from 400 to 700. When you quantify it by measuring how many photons hit a square meter in a second, that unit is called PPFD. And PPFD = PPF.

Photosynthetic Photon (light that is useful for photosynthesis) Flux (photons per area) Density (not sure why they throw density in there because flux says it all).
 
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What's amazing is that sunlight is 2000 um/m^2/s.

I'm sure this has been done but if they took the spectral curve of sunlight, ie how much of each wavelength makes up sunlight and normalized to that curve, you could get a measure of how close a bulb was at replicating sunlight, not just how many photons fall in the range from 400 to 700. Our bulbs probably produce too much of some wavelengths and not enough of others and this would illustrate that difference. Perfectly clear, right?
 
Willistein said:
What's amazing is that sunlight is 2000 um/m^2/s.

I'm sure this has been done but if they took the spectral curve of sunlight, ie how much of each wavelength makes up sunlight and normalized to that curve, you could get a measure of how close a bulb was at replicating sunlight, not just how many photons fall in the range from 400 to 700. Our bulbs probably produce too much of some wavelengths and not enough of others and this would illustrate that difference. Perfectly clear, right?
Click to expand...

it is to me! and that's a totally amazing observation.:cool:
 
I actually did get it but I still got a headache I was looking for a hey dude the reading your gonna get on that meter is the same as a par man so just use it
 
jfl14609 said:
I actually did get it but I still got a headache I was looking for a hey dude the reading your gonna get on that meter is the same as a par man so just use it
Click to expand...



you got it - they are the same number! Sorry, I annoy myself sometimes.... ...many times.
 
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