Lux Meter, Par Meter, whats the difference??

[sc50964]

I did a comparison of lux between the iPhone app and the $15 lux meter from Amazon at a distance of 12" below an Kessil A350W, and the following are the results.

Luxmeter by Galatica (iPhone): 6700
HDE LX-1010B meter ($15 from Amazon): 15000

Now let's apply the 67 lux to par conversion factor for a led that has a 2 to 1 ratio between blue and white.

The iPhone app: 100
The $15 lux meter: 224

Now that's a huge difference, and the following online resource (for an A350 but should be close enough) shows that the par is around 300 at the depth for an A350, whose beam is more concentrated than an A350W. Therefore, i will say that the $15 meter is pretty accurate and a good buy.

 

[saltyfilmfolks]

I did a comparison of lux between the iPhone app and the $15 lux meter from Amazon at a distance of 12" below an Kessil A350W, and the following are the results.

Luxmeter by Galatica (iPhone): 6700
HDE LX-1010B meter ($15 from Amazon): 15000

Now let's apply the 67 lux to par conversion factor for a led that has a 2 to 1 ratio between blue and white.

The iPhone app: 100
The $15 lux meter: 224

Now that's a huge difference, and the following online resource (for an A350 but should be close enough) shows that the par is around 300 at the depth for an A350, whose beam is more concentrated than an A350W. Therefore, i will say that the $15 meter is pretty accurate and a good buy.

THAT is totally cool!!! Thanks!
You probably want an Apogee per meter even more now huh? me too.


btw

whose beam is more concentrated than an A350W.

concentration should only affect intensity, not color

 

[DMan]

Its widely know that par meters aren't very accurate when it comes to blue light. Would a lux meter have the same or any other kind of draw backs when measuring blue/actinic lights.

 

[saltyfilmfolks]

Its widely know that par meters aren't very accurate when it comes to blue light. Would a lux meter have the same or any other kind of draw backs when measuring blue/actinic lights.

mmmm par meters are actually. Read back through the thread.. i think its a good one. worth reading, thanks to all who contributed.

 

[DMan]

mmmm par meters are actually. Read back through the thread.. i think its a good one. worth reading, thanks to all who contributed.

Ok, read and re read. There's info there I just don't agree with. I think there were some good theories, but that's it. Some of the information IMO has been mis interpreted. And some of the explanations are just wrong. Ill say it again. PAR has nothing to do with quality of light.

 

[saltyfilmfolks]

ll say it again. PAR has nothing to do with quality of light.

interesting. Explain please.

 

[DMan]

Couple of bullets taken from articles.
*Measuring PAR
Although Kelvins (as well as LUX conversions using questionable LUX to PAR conversion factors) are ways of getting rough estimates of PAR, only a Specific PAR Meter (also called Quantum Light Meters) which uses a standardized unit of measure can give you the best measurement of this aspect of determining your tanks lighting requirements (both at the surface and under the surface)
*HOWEVER, keep in mind that a PAR Meter is NOT accurate in important light energy spikes WITHIN the 400 to 700 nanometer range, so while one light might measure a higher PAR mmol reading, another light might be still superior due to the more important PUR & PAS output.
This is where I have found the use of a PAR Meter solely to determine light efficiency OVER RATED.
*PAR is an important starting point to estimate light energy, but should NOT totally override the also important related Useful Light Energy (PUR which literally stands for Photosynthetically Useful Radiation). We measure PAR via µMolm which is a unit of measure (more about measurement later).
I have noticed that while PAR is important, it is often used as the only measure by both marine and freshwater plant keeping aquarists, especially by many marketing pros and a popular video channel when PUR/PAS/RQE is ALSO important and should be considered.
*PUR (Photosynthetically Usable Radiation) is something aquarium keepers should concern themselves with along with PAR in providing correct lighting since it describes the quality of light photons as per application

 

[saltyfilmfolks]

Couple of bullets taken from articles.
*Measuring PAR
Although Kelvins (as well as LUX conversions using questionable LUX to PAR conversion factors) are ways of getting rough estimates of PAR, only a Specific PAR Meter (also called Quantum Light Meters) which uses a standardized unit of measure can give you the best measurement of this aspect of determining your tanks lighting requirements (both at the surface and under the surface)
*HOWEVER, keep in mind that a PAR Meter is NOT accurate in important light energy spikes WITHIN the 400 to 700 nanometer range, so while one light might measure a higher PAR mmol reading, another light might be still superior due to the more important PUR & PAS output.
This is where I have found the use of a PAR Meter solely to determine light efficiency OVER RATED.
*PAR is an important starting point to estimate light energy, but should NOT totally override the also important related Useful Light Energy (PUR which literally stands for Photosynthetically Useful Radiation). We measure PAR via µMolm which is a unit of measure (more about measurement later).
I have noticed that while PAR is important, it is often used as the only measure by both marine and freshwater plant keeping aquarists, especially by many marketing pros and a popular video channel when PUR/PAS/RQE is ALSO important and should be considered.
*PUR (Photosynthetically Usable Radiation) is something aquarium keepers should concern themselves with along with PAR in providing correct lighting since it describes the quality of light photons as per application

Can I ask what article those are from and how you measure light?
and the point of the article? and how they recommend reading light?

 

[DMan]

They came from the link I posted earlier. It wasnt something I really looked all that hard for. The information is taken from a number of articles and I suppose some of it is opinion. I've read numerous articles on the subject, including the Advanced Aquarist articles by Dana.
I measure light the same way as everyone else. With a PAR meter. I borrow a friends from time to time ( usually when I get a new light fixture) it the Apogee. I have the Seneye which is handy. I'm not saying anything that was discussed isn't important. We are at a very exciting point in time with regards to the hobby. Just think 20 years ago all we knew was blue light made things look nice. Then we learned white light made things grow fast. Then we get really intense with high output lighting and we blasted everything with light. And that made things look good. Along comes PAR meters and we get a step closer to figuring the puzzle. Recently we learned that spectrum, specfically violet/blue is just as inportant if not more than intensity. And woudn't you know it, it turns out the gadgets we use arent that accurate for what corals need. I love it. I can't wait to see what we figure out next. We are so close.
I not saying the OP is wrong. If they don't want to use a meter to measure specific spots in the tank thats fine. But all I can think is noooo that's exactly what it should be used for. And then the whole lux to par conversion topic came up. And I'm not even going to touch the Iphone apps. All I can say is don't rely on Apple to determine the health of your tanks. All these tools we have at our disposal are great for reference, but we have to remember the limitations. The hobby is still at the stage where corals are classified as being high, moderate, and low light requirements. You won't see this coral needs this many mmol's just yet. But I think soon. I guess I just get frustrated seeing people put to much faith in something we should be taking with a grain of salt.

 

[DMan]

They came from the link I posted earlier. It wasnt something I really looked all that hard for. The information is taken from a number of articles and I suppose some of it is opinion. I've read numerous articles on the subject, including the Advanced Aquarist articles by Dana.
I measure light the same way as everyone else. With a PAR meter. I borrow a friends from time to time ( usually when I get a new light fixture) it the Apogee. I have the Seneye which is handy. I'm not saying anything that was discussed isn't important. We are at a very exciting point in time with regards to the hobby. Just think 20 years ago all we knew was blue light made things look nice. Then we learned white light made things grow fast. Then we get really intense with high output lighting and we blasted everything with light. And that made things look good. Along comes PAR meters and we get a step closer to figuring the puzzle. Recently we learned that spectrum, specfically violet/blue is just as inportant if not more than intensity. And woudn't you know it, it turns out the gadgets we use arent that accurate for what corals need. I love it. I can't wait to see what we figure out next. We are so close.
I not saying the OP is wrong. If they don't want to use a meter to measure specific spots in the tank thats fine. But all I can think is noooo that's exactly what it should be used for. And then the whole lux to par conversion topic came up. And I'm not even going to touch the Iphone apps. All I can say is don't rely on Apple to determine the health of your tanks. All these tools we have at our disposal are great for reference, but we have to remember the limitations. The hobby is still at the stage where corals are classified as being high, moderate, and low light requirements. You won't see this coral needs this many mmol's just yet. But I think soon. I guess I just get frustrated seeing people put to much faith in something we should be taking with a grain of salt.

 

[aereaus]

PUR is photosynthetically useful radiation versus active. I think theyre both pretty useful honestly if you can cover the spectrum.

 

[LostInTheDark]

PUR is photosynthetically useful radiation versus active. I think theyre both pretty useful honestly if you can cover the spectrum.

Is there a method to measuring PUR?

 

[DMan]

I'm not sure it is a measurement. Maybe rather a range. For each subject you are lighting the PUR may change. PAR will give you how much light is availabe for photosynthsis, but PUR will tell you exactly what range of the spectrum will actually be used by whatever it is that is being lit. You may have two bulbs. One has a higher PAR value than the other. But lets say the lower PAR bulb produces better PUR . You would want to use the bulb with lower PAR because it produces better PUR. The higher PAR bulb may produce more intenisity, but it's useless if the spectrum being produced isnt even being used.
It's kind of tough to wrap your head around. Heres another good explanation.
https://orphek.com/pur-photosynthetically-useable-radiation/

 

[RedneckReefer68]

galactica for iphone
lux light meter by crunchy byte box for android. best of 14 I tested.

I have an nexus 6 Android phone for my personal use and an iPhone 5c for my work phone.. The Android phone using lux light meter reads 32000 at water line and the Galactica on iPhone reads 68k... Not sure which one is accurate... Lol

 

[DMan]

I have an nexus 6 Android phone for my personal use and an iPhone 5c for my work phone.. The Android phone using lux light meter reads 32000 at water line and the Galactica on iPhone reads 68k... Not sure which one is accurate... : )

Neither.

 

[RedneckReefer68]

OK accurate might of been wrong word, but with that big of gap one has to be closer to being right than the other. I'm running 250w radium's and m80 ballasts so I prefer the iPhone to be more closer to what the numbers actually are. Lol

 

[DMan]

Sorry I wasnt trying to give you a hard time. Im just skeptical because I guess the phones use the camera to measure the light. Maybe the technology is the same as a Quantum meter. The Seneye meter works pretty much the same and the software does the conversion. But it wont even register the blues. It reads my refugium 6500k bulb accuratley but I think anything above 10000k it loses its accuracy. I think the phones would work much the same way. And plus a lux meter is measuring the spectrum that the human eye is most accurate at. But for reference it still a great tool. Especially with Leds, which can have hot spots that you can identify. Of course the meter has to be waterproof to ddo this.