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PAR meter using iPhone / Android APP - does it work?

Yugang

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Does anyone have experience using iPhone / Android apps for the measurement of PAR in our planted tanks? It seems we just put the iPhone in a plastic bag, and here we go. Is it that easy?

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Several APPS are available for iPhone and Android, as an alternative to more expensive dedicated meters (e.g. Apogee), with 5-10% compromise on accuracy for the best performers.

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Some more detailed info/claims from the Photone APP:

1702111432821.png

I downloaded Photone App, but really have no idea yet how it works, nor do I have any experience with PAR measurements or Apogee. Could anyone share experience with Photone?
 
I was thinking about using this app as well after reading this thread on reef2reef Free PAR meter? Photone App.. Apparently it's very accurate, at least for reefers. Though I hear it's more accurate on iphones since they did the app testing/calibration for iphones. It looks like I can calibrate on android If I get a PAR meter to reference. I might try renting a PAR meter to test this.
 
I purchased the Photone app option "LED full spectrum" (about 6 USD), used some printer paper as diffuser on my iPhone front camera and put the phone in a small plastic bag.

In my tank I measure PAR 120 micro mol/m2/s at substrate, which seems to be in the "high light" range. I am using 2 Juwel Spectrum, 48 Watt each, on my 50 gallon tank (39*18*23 inch). I now have a PAR measurement, but I can't say how accurate it is.

I took this screenshot from How to read PAR tables
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Would it be fair to conclude that as long as we are not by more than 25% off for our PAR measurement, we are accurate enough for a planted tank? What would be the point of investing $$$ for more accuracy?

Note: IMO calibration would a.o. be helpful to mitigate the impact of using various printer papers (with different optical properties) as diffusers in front of the phone's sensor. It would be nice if we could buy calibrated white light sources (as simple as an IKEA LED for home lighting, but slightly more expensive as they have been factory tested and are provided with their test data), so that we can calibrate our iPhone PAR measurement apps without having to rent an Apogee meter. If we need to rent an Apogee anyway, there is no point in using the iPhone App.
 
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I think there in lies the problem. It’ll vary from person to person with the diffusion, not to mention what does “led full spectrum” even quantity to. Some experimentation as you’ve indicated with known values would certainly help. $6 is quite the bargain, I think we need someone with a meter to test this app to see how close it can truly get.
 
In the ranking of important contributors to success, and failure, we have light, CO2 and ferts in the top.
It is fascinating that in our hobby we optimise the ppm's for Macro and Micros', 15 of them, in big spreadsheets while ferts do not need to be a main cause of failures if we simply take (some derivative of) EI, i.e. overdose a bit, and do regular (soft) water change.
We then still have CO2 and light to optimise our chances for success, but very few of us actually measure/optimise pH profiles for CO2 and only the advanced hobbyists measure light in the tank. I personally believe that this is an issue of tradition and knowledge, not of technology or budget.
Even if not very accurate, a simple and affordable light measurement may be part of the solution. When we more often measure and report PAR, we may also gradually build a better quantitative understanding how we balance light PAR with CO2 ppm, and how the combination of both relates to plant health and algae.
 
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This is an interesting topic. I have a PAR meter and I will be happy to compare. What app would you like me to start with?

I used Photone and purchased the LED full spectrum option.

The first would be to understand what do you expect from your PAR meter, and how are you using it.
  • How often do you use your PAR meter?
  • How many locations in your tank would you check?
  • How accurate do you want to know your PAR number, could you live with +/- 5%, +/-20% or even +/-50%?
  • In your view, how does PAR help you to understand and optimize your planted tank?
  • Why is it that Reefers talk much more about PAR than planted tankers?
There are several YouTube videos for Reef tanks (with Reef tank lighting spectrum) comparing a dedicated PAR meter with an IPhone App. I can’t comment on the quality of these, or whether some may be sponsored/less objective. It would be helpful to have some comparison data for planted tanks
  • Compare Apogee PAR measurement with iPhone app for planted tank, with ‘full spectrum LED’ selected as light source.
  • What is roughly the % difference between Apogee and iPone App, and is this an acceptable accuracy for you?
  • When you change the color spectrum of your lighting (assuming your light source can do that), will you find the same accuracy for the Apogee compared to iPhone App?

Overall, if we assume that PAR measurement will be both cheap and easy, how much would these contribute for planted tanks?

Perhaps it is too much to ask you all these questions @fablau , but hope that others may chime in as well to educate me. I have really no experience with light measurement.
 
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Hope it's ok to ask here, since the discussion is about PAR..

I had the LFS guy come and test my lights with an Apogee PAR meter recently......

I have Week Aqua a430 pro lights, at 80% the lights measured 125-130 at the substrate. I assumed that was the PAR, but I'm not so sure about the numbers now, because after reading on the 2hr aquarist site, on one article there is a conversion rate of 1.32 that needs to be applied.


Could anyone shed some light on this for me?

(pun not intended 😆)
 
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Boy this thread has a lot of good discussions on it. I too think it would be great for us to get a better understanding of how to measure PAR and read PAR tables correctly.

My two cents is that the app can be a worthwhile investment if you don't want to spring for a dedicated par meter. I even wouldn't worry too much about its accuracy as what it can tell you is trends. If you have concerns that light may be a limiting factor to growth, take a measurement with the app and see what it tells you.

If you have a light that allows up increasing power, increase it then take another reading. If the number is higher, you are going in the right direction. Observe your plants for a week or two for improvement. Then keep tweaking until you find the right balance for your plants.

It's not about hitting a number. It's about finding the right number for your tank.
 
I'm not too worried about absolute numbers either, I've experimented with my lights on different intensity levels throughout the last 18 months. It's more of a learning experience for me and just out of curiosity. I have a reasonable idea of what my lights are capable of without being concerned about exact numbers.

I know of some people who run their week aqua a430 lights at 100%, 200+ PAR and their tanks are fantastic, demonstrating a high level of skill, but for me, I find it difficult to manage the tank using that level of light. I guess it depends on the type of plants, but more importantly, the maintenance and skill level required, which is something I need to develop.
 
there is a conversion rate of 1.32 that needs to be applied.
Could anyone shed some light on this for me?

Quantum sensors (often called PAR sensors) are increasingly used to measure photosynthetic photon flux density (PPFD, units of µmol m-2 s-1) underwater, which is important for biological, chemical, and physical processes in natural waters and in aquariums. When a quantum sensor that was calibrated in air is used to make underwater measurements, the sensor reads low.
This phenomenon is called the immersion effect and happens because the refractive index of water (1.33) is greater than air (1.00). The higher refractive index of water causes more light to be backscattered (or reflected) out of the sensor in water than in air (Smith, 1969; Tyler and Smith, 1970). As more light is reflected, less light is transmitted through the diffuser to the detector, which causes the sensor to read low. When this effect is not corrected for, underwater measurements are only relative, which makes it difficult to compare light in different environments.


Note @Joel Armstrong I am reading that some meters may have an 'underwater' option, where the correction is automatically applied for you. I guess that for others you need to do your own correction. Best would be to refer to the manual of your meter, or reach out to manufacturer.
 

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read PAR tables correctly.
I had a look at some manufacturer's sites and threads on other fora, and my take away is that without a good understanding of optics it is not unlikely to misinterpret these PAR tables. One could try and compare two LED products of same size to have a feeling before deciding which one to buy, but it is IMO better to be very cautious trying to translate that into real life PAR values in the tank.

I limit myself to two examples, few on this forum will be interested to hear more than that.

For a light point source indeed the intensity goes down by the square of the distance between source and detector. But for a line source (long fluorescent tube or LED bar) this is NOT longer true, it goes down by the distance (rather than distance squared). For a line source with finite length (like 3 feet), what happens in the centre of the tank is totally (like 50-100%) different from the left or right end of the tank. This is just one example (I mention this one as I see posts on other fora that are incorrect in this regard).
Another factor that leads to misinterpretation is that many LEDs have small lenses in front of them, so in real life they do not irradiate light as a simple point source but indeed as a focussed beam. To some extent it will be reflected in the PAR table, but again very easy to misinterpret to a real life tank situation.

For a theoretical understanding the light pattern in the tank, a physicist would probably use Monte Carlo computer modelling techniques, ray tracing, as there are no easy ways to calculate or understand with mathematics. So this leaves measurement, rather than calculation, as the most practical approach to know the PAR distribution in a real life tank.

If any manufacturer disagrees to above and/or can help to understand how to translate a PAR table to my real life tank, I would welcome them to chime in here.

Note: I would prefer manufacturers to provide measured PAR data from real water filled tanks with commonly used tank dimensions. A graph, with the PAR data over the full bottom rectangle of the tank, without much room for misinterpretation, that would be great.
 
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Quantum sensors (often called PAR sensors) are increasingly used to measure photosynthetic photon flux density (PPFD, units of µmol m-2 s-1) underwater, which is important for biological, chemical, and physical processes in natural waters and in aquariums. When a quantum sensor that was calibrated in air is used to make underwater measurements, the sensor reads low.
This phenomenon is called the immersion effect and happens because the refractive index of water (1.33) is greater than air (1.00). The higher refractive index of water causes more light to be backscattered (or reflected) out of the sensor in water than in air (Smith, 1969; Tyler and Smith, 1970). As more light is reflected, less light is transmitted through the diffuser to the detector, which causes the sensor to read low. When this effect is not corrected for, underwater measurements are only relative, which makes it difficult to compare light in different environments.


Note @Joel Armstrong I am reading that some meters may have an 'underwater' option, where the correction is automatically applied for you. I guess that for others you need to do your own correction. Best would be to refer to the manual of your meter, or reach out to manufacturer.

I appreciate your detailed response, thank you 😊
 
Note @Joel Armstrong I am reading that some meters may have an 'underwater' option, where the correction is automatically applied for you. I guess that for others you need to do your own correction. Best would be to refer to the manual of your meter, or reach out to manufacturer.

Just out of interest, I contacted the LFS to see exactly what meter they used to test my lights. It was an Apogee MQ-510. As stated in the link, the meter factors in the conversion rate.

 
Note: I would prefer manufacturers to provide measured PAR data from real water filled tanks with commonly used tank dimensions. A graph, with the PAR data over the full bottom rectangle of the tank, without much room for misinterpretation, that would be great.
Another note to manufacturers....

Many years ago, as a physics student, I have actually written software to calculate optics with Monte Carlo methods, so I know what it takes. Modern day PC's are now so fast, that it is feasible to achieve reasonable accuracy for the calculations within acceptable CPU times.

How beautiful would it be if you let a university physics student code a Monte Carlo ray tracing program for you, include your proprietary optical data for the LED's of your products. Hobbyists can download your tool, set up their tank dimensions, adjust setting of RGB channels in the simulation software, and then let it calculate and display the PAR distribution and spectrum in their tanks?

It would not only be a great service to the hobbyists, but a great marketing tool for your products as well.

Just imagine, we could set up our LED channels to get to our target PAR, and know the spectrum and light distribution in our tank without the need for a PAR meter or any wet hands.
 
Bulk Reef Supply did a nice video series on how they measure reef lighting. It definitely has enough info to give us something to think about.

 
I used Photone and purchased the LED full spectrum option.

The first would be to understand what do you expect from your PAR meter, and how are you using it.
  • How often do you use your PAR meter?
  • How many locations in your tank would you check?
  • How accurate do you want to know your PAR number, could you live with +/- 5%, +/-20% or even +/-50%?
  • In your view, how does PAR help you to understand and optimize your planted tank?
  • Why is it that Reefers talk much more about PAR than planted tankers?
There are several YouTube videos for Reef tanks (with Reef tank lighting spectrum) comparing a dedicated PAR meter with an IPhone App. I can’t comment on the quality of these, or whether some may be sponsored/less objective. It would be helpful to have some comparison data for planted tanks
  • Compare Apogee PAR measurement with iPhone app for planted tank, with ‘full spectrum LED’ selected as light source.
  • What is roughly the % difference between Apogee and iPone App, and is this an acceptable accuracy for you?
  • When you change the color spectrum of your lighting (assuming your light source can do that), will you find the same accuracy for the Apogee compared to iPhone App?

Overall, if we assume that PAR measurement will be both cheap and easy, how much would these contribute for planted tanks?

Perhaps it is too much to ask you all these questions @fablau , but hope that others may chime in as well to educate me. I have really no experience with light measurement.

I am sorry for the late reply, I had a crazy week. I'll post a detailed response to your questions tomorrow morning, and I'll also measure my BYL LED light with both my PAR meter (Apogee MQ200) and your app with your same option (LED full spectrum), and I'll report here.
 
I am sorry for the late reply, I had a crazy week. I'll post a detailed response to your questions tomorrow morning, and I'll also measure my BYL LED light with both my PAR meter (Apogee MQ200) and your app with your same option (LED full spectrum), and I'll report here.
Thank you @fablau . With hindsight I believe I over asked, but anything you can do is greatly appreciated.
 
Ok, here I am!

I spent about 30 minutes testing the Photone app with the LED full spectrum option, and the results are NOT good. I am sorry. I set the app in "PAR Meter" mode with the "LED Full Spec" set at the bottom, and the numbers I read, compared to the Apogee, are the following:

Apogee: 80 PAR (my tanks substrate) -----> App: 16
Apogee: 100 PAR -----> App: 21
Apogee: 150 PAR -----> App: 23
Apogee: 200 PAR -----> App: 28

I really can't make sense of it. I put the app and the meter in the same exact position with the same angle relative to the light. I have noticed that the Apogee is much more stable, and I mean, even if you change the angle a little, it doesn't change the value much (+-10) but the app can drastically change the result if you put it in a different angle, which doesn't make sense (+-30). Also, it is very unstable; sometimes I read crazy values by moving it, I read a few times values around 400 PAR when the Apogee measured just 100. It is very unreliable and, in my opinion, completely unusable. I am very sorry. It is also true that the app shows a warning that says "Diffuser Required," which could maybe improve the results. But I have no idea how much. But I certainly wouldn't spend money for a diffuser since, as you can read below, I think a PAR meter is absolutely NOT necessary.

I find the Light Calculator on rotalabutterly.com to be much more precise:


If I enter my tank's values, I get 76 PAR at the substrate, which is not too far from the 80 I read with the Apogee.

Please, see below my answers to your questions, in context:


I used Photone and purchased the LED full spectrum option.

The first would be to understand what do you expect from your PAR meter, and how are you using it.
  • How often do you use your PAR meter?

Almost never. I bought it when I was trying to understand if I had too much or too little light 10 years ago, but I haven't used it ever since. Some friends asked me to borrow it once in a while, though ;)

I would probably use it if I were changing the landscape or setup of my tank. But otherwise, I would not recommend buying it. It is much better to use the online calculator I mentioned above. And other reasons are explained below...

And, of course, I used it to find the perfect spot for my Orchids ;)

  • How many locations in your tank would you check?

If you had a PAR meter, I would recommend checking the bottom first, in 9 locations:

left-back
center-back
right-back
left-middle
center-middle
right-middle
left-front
center-front
right-front

That way, you can understand if your light is consistent through the tank. In my case, my PARs go down a great deal at the sides, so I know to put low-light plants in there ;)

You might also want to measure about 3 inches from the surface, just to have an idea of the "light curve." If you see the curve being too steep (for example, 80 PAR at the bottom and 200 PAR at 3 inches from the surface), you may want to try to screen or lower your light so to have something like 60 PAR at the bottom and 120 at 3 inches. But the situation may vary a lot according to the layout, other plants, wood, rocks, etc. But I wouldn't be that paranoid unless you like to play and tinker with that stuff... as I said, I would not recommend spending $300+ for a PAR meter, it is actually NOT needed if you use the online calculator and you aim for 60-80 PAR at the substrate, you can go up to 100 or more if you want really strong light. That's a good starting point, and the rest of the measurements don't make much difference IMO.




  • How accurate do you want to know your PAR number, could you live with +/- 5%, +/-20% or even +/-50%?

Well, I wouldn't go over 20%. For example, if you have an actual PAR measure of 80 at the substrate, and your meter gives you 60, that'll be ok anyway. But if you have 80 at the substrate and you measure 40, you will want to increase your light to aim for 80 at the substrate, when in reality, you could have 100-120, which could be much more light than what you'd want, and such a difference would make a huge difference in plant growth and, mostly, plant demand.



  • In your view, how does PAR help you to understand and optimize your planted tank?

I think it can be used to "learn" and "understand" how light reaches your plants and how much that can vary according to your layout, location, etc. But once you understand that, the same will apply pretty much to any tank setup, and you'll know already to avoid putting plants that need more light on the sides or at the bottom covered by other plants, etc... often good sense corresponds to what you learn from using it ;)


  • Why is it that Reefers talk much more about PAR than planted tankers?

I think because of coral, but I don't know anything about reef tanks (!!!), I guess the video posted above could help with that ;)


There are several YouTube videos for Reef tanks (with Reef tank lighting spectrum) comparing a dedicated PAR meter with an IPhone App. I can’t comment on the quality of these, or whether some may be sponsored/less objective. It would be helpful to have some comparison data for planted tanks
  • Compare Apogee PAR measurement with iPhone app for planted tank, with ‘full spectrum LED’ selected as light source.

Yes, I answered this at the beginning of this post.

  • What is roughly the % difference between Apogee and iPone App, and is this an acceptable accuracy for you?

Too much, as I read above, I measured 80-100% differences. Not good...


  • When you change the color spectrum of your lighting (assuming your light source can do that), will you find the same accuracy for the Apogee compared to iPhone App?

I noticed no difference, I got the same skewed results.


Overall, if we assume that PAR measurement will be both cheap and easy, how much would these contribute for planted tanks?

Well, if it were cheap and easy, I would say that could give a good starting point for choosing and setting up the correct light for your situation. I'd say, if you'd want a low-light, low-maintenance tank, aim for 30-40 PAR max at the substrate, with peaks of 100 at the surface. If you'd want MID light, aim for 60-70 at the substrate, with peaks of 120-150 at the surface. If you'd want HIGH light, you can start from 90 at the substrate, and have 200 or more at the surface. More light ---> more growth ---> more demand ---> more work ;)



Perhaps it is too much to ask you all these questions @fablau , but hope that others may chime in as well to educate me. I have really no experience with light measurement.


It's never too much! I hope this helps, and please let me know if you have any more questions or doubts.

All the best,
Fab.
 
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