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Lux to PAR conversion 7300K LED

6408 Views 15 Replies 6 Participants Last post by  Maryland Guppy
I know this topic is touchy, I've been investigating for days.

I also realize we are speaking two different measurements here.
There had to be some continuity between them though.

After downloading lux and lumen meter apps things came to mind.
I couldn't find multipliers for the conversion and no LED PAR data.
Many other multipliers but not for many LED types or colors.
CFL, MH, T8's, T5's could all be found.

I am new to planted tanks for the most part.
Other than raising Molly fry in the 70's with floating hornwort that's it. :icon_smil
Panther groupers and triggerfish in the 80's doesn't really count.

I may have found some resemblance of proof through Dana Riddle's studies.
Apparently a credited individual on lighting studies and other useful info.
I don't know if I can link to the articles I have found, simple research will provide though.

Using 7300K LED's of no specific brand a multiplier of .0222 to lux will
provide a fairly good estimated PAR value.
This has been mentioned in the forum before.
Finding some proof from a case study settled my unrest.
I feel lucky I picked 7300K lamps for my LED project,
other Kelvin ratings did not fare as well.

Any thoughts on this?
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Any thoughts on this?
Well comparing something that measures this:

The spectral sensitivity curve for photographic meters is intended to reproduce V-lambda, the standard spectral sensitivity curve for human photopic vision, but may be modified by the manufacturers to more closely resemble the response of photographic emulsions. Some firms regard their meters’ spectral sensitivity curve as a trade secret. Gossen’s curve (courtesy of Günter Bauer, Gossen-Photo) is reproduced here, with V-lambda superimposed for comparison:
And converting it to this:


from light sources that look like this:


is always a bit problematic..
;)
 

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For most aquarium light sources you can divide a lux reading by about 70-76 and get a reasonable estimate of PAR. When you have LED lights with a lot of the light coming from the near UV and near IR parts of the spectra this is a lot less accurate. There can never be a really accurate way to convert a lux meter reading to a PAR reading that will work for all light sources.
 

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For most aquarium light sources you can divide a lux reading by about 70-76 and get a reasonable estimate of PAR. When you have LED lights with a lot of the light coming from the near UV and near IR parts of the spectra this is a lot less accurate. There can never be a really accurate way to convert a lux meter reading to a PAR reading that will work for all light sources.
Lux to PAR Conversion Factors

If you have a lux meter, it is possible to convert lux measurements to PAR values. Use these results with some caution - in most cases it would be safe to assume the results will be low.

  • Divide blue (450nm) LED Lux by 69
  • Divide white (7,300 K) LED Lux by 45
  • Divide blue (450nm)/white (7,300 K) combination LED (2:1 white/blue ratio) Lux by 67
http://www.advancedaquarist.com/2013/2/equipment

The orig. O/p's data source

Similarly, the Apogee did very well in 'sun' mode when analyzing the output of 7,300 K white LEDs. In addition, the Apogee and FieldScout meters repeatedly performed best when measuring sunlight when in the 'electric' setting.

Based on these observations, inexpensive PAR meter have some utility for measuring light produced by LEDs
 

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Discussion Starter · #6 ·
Sorry guys, I just needed something to go by for a new planted tank.
I had to have some sort of guideline to follow.

To continue this conversation what PAR constitutes Hi ,Med, and Lo light?
Seeing that I will be using these values for a lux to PAR conversion.

Any factor for light through water, I've measured in an empty tank?
 

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Sorry guys, I just needed something to go by for a new planted tank.
I had to have some sort of guideline to follow.

To continue this conversation what PAR constitutes Hi ,Med, and Lo light?
Seeing that I will be using these values for a lux to PAR conversion.

Any factor for light through water, I've measured in an empty tank?

 

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The light intensity in a planted tank, which is lighted by anything other than sunlight, varies greatly from one spot to another in the tank. The closer to the water surface, the higher the intensity. The closer to the center of the tank the higher the intensity. The intensity under plant leaves is lower than unshaded areas. A PAR reading at the substrate level, in the center of the tank, can be used to judge the overall light intensity in the tank, and that is what I am referring to any time I mention PAR readings. Because the range of intensities in the tank is different when the light is hanging high above the tank vs when it sits right on top of the tank, it isn't possible to use a single PAR number that exactly determines the over all light intensity for all tanks. So, when we say 20 to 40PAR is low light, that is just an approximation, not a cast in stone hard value. With those things in mind: I believe that 20-40 PAR can be called low light - CO2 is not essential for growing plants and avoiding algae problems. 40-60 PAR can be called medium light - CO2 is highly desirable, but Excel may be adequate. Above 60 PAR can be called high light - CO2 is essential for growing plants without almost inevitable serious algae problems. I may change my mind on those numbers at any time!!
 

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Discussion Starter · #9 ·
These were all the lux measurements for plant possible areas in my tank.
I converted to PAR by /45 method. I had to estimate somehow.
All low to almost medium plant light requirements.
Photograph White Atmosphere World Display device


Photograph Display device Snapshot Photography Silver


This still leaves a wide variety of plants to choose from.
At least I am planning for success.

Thanks everyone for the information and replies!

The next issue will be CO2.
In a low to medium lighting tank would homemade CO2(bottle brew) help.
It would be used at low levels and in moderation.
I feel it would improve plants even though not required.
 

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What kind of hardscape is that?

If you ask me...

There are no magic numbers.
Get something that you can dim and play around until you have the levels you want while algae is under control. Trying to hit a certain range of PAR will not necessarily be what you want given 1000 other factors specific to your tank.

I think people get way too technical - it's really not all about the numbers from what I have experienced...

IMO the best thing you can do at the start is get a light you can dim and figure out what works for you. Start slow.
 

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Discussion Starter · #11 ·
Landscape made from styrofoam, silicone together, covered with mortar/stucco.
I am on my third coat of mortar tonight.
By the end of the weekend I hope to cure in the tank.
I am hoping to have live plants by Christmas.
This may not happen due to curing process.
 

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What kind of hardscape is that?

If you ask me...

There are no magic numbers.
Get something that you can dim and play around until you have the levels you want while algae is under control. Trying to hit a certain range of PAR will not necessarily be what you want given 1000 other factors specific to your tank.

I think people get way too technical - it's really not all about the numbers from what I have experienced...

IMO the best thing you can do at the start is get a light you can dim and figure out what works for you. Start slow.
The reason people want to figure these things out is because it cost money to do it other ways. At some point I imagine every light will include dimmers and timers for fairly cheap. But right now if you think about over doing it on light then trying to dim down you are over paying for the light itself then adding the cost of dimming. This can easily add up to hundreds of dollars. The numbers allow a person to compare lights, and to get enough information that they can hopefully get close to the right amount of light for a setup. Then if they need to go down a little they can raise the lights.

On top of that quantifiable measures are pretty much the only way most of us have to get us to try new lights. That is how we can compare them to existing known lights and get a idea of how many and how much it will cost for a setup.
 

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Discussion Starter · #13 ·
http://www.plantedtank.net/forums/showthread.php?t=774226

Another post I started, first one.
Thought it would provide options for some.

LED's, drivers, dimming, I don't care.
I can build it and it will run cool.
If I need more light I'll add another strip of LED's or change wattage.

I just want a sustainable amount of easy plants and Guppies :icon_smil.

LED lighting is in it's infancy at this time.
No standards in lamps or drivers exist.
PWM is standard in many other applications and is being applied to LED lighting.
All manufacturers are building what they think the market will take.
Many LED lamps are also losing their market appeal.
Higher voltage LED's are almost out of stock with no more production.
Many vendors are only selling until stocks are depleted.
Drivers have also changed only to drive the new lamps.
I am only talking about components here not fixtures.

I wish to get a programmable controller in the future.
Sunrise and Sunset with dimming over time.

Much thanks to the replies and insight for lighting.

I guess I should start a thread about my aquascape!
 

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On top of that quantifiable measures are pretty much the only way most of us have to get us to try new lights. That is how we can compare them to existing known lights and get a idea of how many and how much it will cost for a setup.
All fine and dandy.. except every ballpark measurement and calculation is prone to multiple errors..
Coming "close" is the best one can do really.
erring on the low side is usually more costly.. i.e adding another fixture..but good for manuf... ;)


On a personal note.. there shouldn't be an LED aquarium fixture w/ out dimming.. since no matter how it is designed (constant current or voltage) the "tech" is dirt cheap.........
http://www.micromark.com/LED-Strip-...n=GoogleBase&gclid=CO2Avrihw8ICFREdaQodfJkACw
 

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Discussion Starter · #16 ·
I'm thrilled there is still some interest.
Here is where I am today.
Nature Vegetation Blue Organism Natural environment

It is a small jungle, no particular theme or scheme.
This tank was set up for me to discover different plants.
Almost all plants were rescued from LFS's in my area.
Most were damaged and free or bought for $1 each.
I've been able to try tissue cultured, potted, stems, and severely damaged java fern, etc.....

DIY CO2 turned into dosing ferts, now I struggle keeping nitrogen above 5ppm.
Water clarity is pristine with 5 micron media usage every 2 weeks for 2 days.
Purigen is a blessing in disguise.
 
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