# How to find what par my LED light is



## Seattle_Aquarist (Jun 15, 2008)

Hi rstampa,

Contact @Hoppy on this forum, I believe he may have a meter that he rents at a reasonable price.


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## Kalyke (Dec 1, 2014)

Did you get any flyer or info with the light? I just got some terrestrial plant LED grow lights and a flyer was in the box telling me the par for Red (620-625) and the par for Blue (460-465). I would think that spectrum the plant does not use (middle/green) would not be included in the bulbs. The lux meter I have shows only Lux and FC. Heighth is also going to be important in the equation. 

Calling tech or customer support at the company may help as well.


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## jeffkrol (Jun 5, 2013)

Use a lux program on a cellphone to "guesstimate PAR.
Divide LUX by 67....



> ... in the box telling me the par for Red (620-625) and the par for Blue (460-465). I would think that spectrum the plant does not use (middle/green) would not be included in the bulbs........


Those are the wavelenght numbers not PAR...


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## clownplanted (Mar 3, 2017)

Interesting that my post stating I can rent my par meter got deleted. Is there a reason I cannot rent my par meter to someone here? 


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## Seattle_Aquarist (Jun 15, 2008)

Hi @rstampa & @Funken_A,

Possibly you can reach him here; try a PM.
@clownplanted....likely because you were offering to sell/rent outside of the FST sub-forum.


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## clownplanted (Mar 3, 2017)

Seattle_Aquarist said:


> Hi @rstampa & @Funken_A,
> 
> 
> 
> ...




Interesting. Did not know that. Now I do. Sure it's in the rules. I hate reading rules lol. Either way no problem. 


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## Veritas (Aug 9, 2013)

Funken_A said:


> Been searching for Hoppy looks like he had a falling out with the mods. and is no longer here


oh my gosh. I just found that thread. what a shame....he was definitely one of the most valuable members of this community! :frown2:


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## charlie 1 (Oct 22, 2006)

Veritas said:


> oh my gosh. I just found that thread. what a shame....he was definitely one of the most valuable members of this community! :frown2:


Could not agree with you more, one of the very few that I have a high respect for .
A real shame!


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## Kalyke (Dec 1, 2014)

jeffkrol said:


> Use a lux program on a cellphone to "guesstimate PAR.
> Divide LUX by 67....
> 
> 
> ...


The photosynthetic active radiation (PAR) IS a wavelength.


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## jeffkrol (Jun 5, 2013)

Kalyke said:


> The photosynthetic active radiation (PAR) IS a wavelength.


Not the quantity. just the band..
Red 620-625nm
Blue 460-465nm
Has nothing to do w "counting" PAR.. just at what wavelength the LED emit at..


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## Kalyke (Dec 1, 2014)

The way I am reading this is that the original poster wants a measurement of intensity, and not PAR. Measuring LUX or FOOTCANDLES is useless for plants because they do not use those wavelengths of light.

https://www.extension.purdue.edu/extmedia/ho/ho-238-w.pdf

PAR is a range of light waves used by plants to photosynthesis. They are red, and blue. Nothing else matters in photosynthesis. 

The poster said


> I have no idea what PAR it is and if it is strong enough to grow my plants.


 The poster is equating "strength" with frequency. 

To get "strength" or intensity of light you would look at a measurement of Lux or FC.


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## jeffkrol (Jun 5, 2013)

Kalyke said:


> The way I am reading this is that the original poster wants a measurement of intensity, and not PAR. Measuring LUX or FOOTCANDLES is useless for plants because they do not use those wavelengths of light.
> 
> https://www.extension.purdue.edu/extmedia/ho/ho-238-w.pdf
> 
> ...


Not even close to correct..
Well a bit.. but broadly speaking..









http://www.apogeeinstruments.com/conversion-ppf-to-lux/



> Red 620-625nm


you can have any "PAR" value from 1 to infinity at that wavelength.. Tells you nothing about intensity..

PAR or more correctly PPFD is a measurement of moles of photons/area/time for wavelengths between 400-700nm.
It is more of a "convention" in order for people to talk the same language.
you can argue that some "bands" should be weighted.. thus PUR (photosythetically useable radiation) but plants can utilize ALL visible light ..just are more efficient in some areas.. 
LUX to PAR is a broaad conversion based on some assumptions of spectral composition.
also is it is VERY poor w/ dealing w/ narrow spectrum lights..esp. blue/red rich.
You cannot estimate PAR using LUX w/ a horticulture LED.

http://www.olino.org/us/articles/20...ment-data-lamp-measurement-articles#S/P-ratio
http://www.olino.org/us/articles/2013/10/13/led-e-lux-led-floodlight-aim

A "green only" light may have a PAR value of 100 but it's "PUR" may be only 50 due to poor quantum efficiency..


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## steveo (May 25, 2012)

jeffkrol said:


> Use a lux program on a cellphone to "guesstimate PAR.
> Divide LUX by 67....
> 
> 
> ...


Just downloaded the LX Light Meter app for android phones off google play store. This is too cool! You made it clear, that using a tool like this to obtain Lux, then dividing by 67, would provide a 'guestimate' PAR value. I used this method on my Marineland Aquatic Plant light and got a very realistic PAR value. Out of curiosity, how was the value of 67 obtained? Thanks!


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## jeffkrol (Jun 5, 2013)

steveo said:


> Just downloaded the LX Light Meter app for android phones off google play store. This is too cool! You made it clear, that using a tool like this to obtain Lux, then dividing by 67, would provide a 'guestimate' PAR value. I used this method on my Marineland Aquatic Plant light and got a very realistic PAR value. Out of curiosity, how was the value of 67 obtained? Thanks!


Others who did comparisons..Think Hoppy came up w/ 70..

74 for cool white fluorescent (also phosphor converted light.).
Between the Cannabis growers and orchid people there is a lot of raw data..
Lux to Par to PPFD Conversion Charts | Rollitup

I initially assumed between daylight (54) a cool white flour. (74).. 64..


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## steveo (May 25, 2012)

jeffkrol said:


> Others who did comparisons..Think Hoppy came up w/ 70..
> 
> 74 for cool white fluorescent (also phosphor converted light.).
> Between the Cannabis growers and orchid people there is a lot of raw data..
> ...


Thanks! This is really good info.


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## jeffkrol (Jun 5, 2013)

steveo said:


> Thanks! This is really good info.


You're welcome.. As long as you are just going like 10 vs 40PAR.
Doing like 48 or 50 is pointless .. well even w/ a good PAR meter but that is another story..


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