# Lux Meter



## joebob296 (Sep 30, 2016)

Hello, 

I'm trying to determine how much light my tank has. Right now I have 32 5 watt Cree leds on a 100 gallon tank. As iI do not have acces to a par meter I read about using a lux meter on my phone. For those of you who use lux apps, what ones do you use? Also, how do you interpret lux into par? It can be either IOS or Android. Thanks in advance.


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## micheljq (Oct 24, 2012)

Hello, i did use the one from Whitegoods this summer on my iPhone and liked it. I did not try to convert to PAR readings.

Michel.


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## joebob296 (Sep 30, 2016)

Ok, I'll check it out. So what did you do with the information. I mean if I find out that I have x amount of lux, what does that tell me?


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## Hoppy (Dec 24, 2005)

Divide the lux by 70 and you have a rough estimate of the PAR. This is good enough to decide if you have low light, medium light, etc., but that's all, and that's all we need most of the time. You can assume that 20-35 PAR is low light, 40-50 PAR is medium light, and up to 90 PAR is high light. These are measurements of intensity at the substrate surface. You always have higher PAR readings higher up in the tank, but those numbers at the substrate are one way to define the light intensity in the tank. (High light is when you have to use pressurized CO2 to avoid big algae problems, medium light is when CO2 is very effective, but can be DIY CO2, and low light is when many plants will grow well without adding any CO2, even though CO2 is still very helpful to the plants.)


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## joebob296 (Sep 30, 2016)

Hoppy said:


> Divide the lux by 70 and you have a rough estimate of the PAR. This is good enough to decide if you have low light, medium light, etc., but that's all, and that's all we need most of the time. You can assume that 20-35 PAR is low light, 40-50 PAR is medium light, and up to 90 PAR is high light. These are measurements of intensity at the substrate surface. You always have higher PAR readings higher up in the tank, but those numbers at the substrate are one way to define the light intensity in the tank. (High light is when you have to use pressurized CO2 to avoid big algae problems, medium light is when CO2 is very effective, but can be DIY CO2, and low light is when many plants will grow well without adding any CO2, even though CO2 is still very helpful to the plants.)


Thank you for the information! That is exactly what I'm looking for. Now, I just downloaded 2 different lux meter apps using IOS, and on one app I got 6844, on the other I got 9520. I think these numbers are bogus. If I divide the lower number by 70 it shows that I have 95 lux. I set my phone flat on the substrate and took a screenshot. I'm going to try doing this on Android and see what I get. Will report back soon.

EDIT: I just downloaded 3 different apps using Android and I got an average of 76 lux...I have no idea what is going on.

Edit 2: For info on my lights, here was a thread that I started awhile back. The lights are 31 inches off the substrate, tank is 24 inches high.
http://www.plantedtank.net/forums/100-low-tech-forum/1086217-help-setup-decisions.html


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## jeffkrol (Jun 5, 2013)

You mean 76PAR right? At what height?
Your CREE lensed emitter are quite efficient..


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## joebob296 (Sep 30, 2016)

jeffkrol said:


> You mean 76PAR right? At what height?
> Your CREE lensed emitter are quite efficient..


Well, I think it was user error, I was using the back camera and it was set up to use the front. With my error out of the way, I got an average of 6500 lux. I used multiple apps, multiple times on both IOS and Android and took the average of them all. Divide that by 70 = 92par? Is that corrrect? lights are 31 inches off substrate. I can raise and lower as needed.


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## jeffkrol (Jun 5, 2013)

92 PAR w/ a camera to light diode distance if 31"? Just verifying.

If correct you have solid high PAR even accounting for "errors"..


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## joebob296 (Sep 30, 2016)

jeffkrol said:


> 92 PAR w/ a camera to light diode distance if 31"? Just verifying.
> 
> If correct you have solid high PAR even accounting for "errors"..


Yep, just verified height. It's exactly 31 inches from top of substrate to diode. Obviously, tank has no water in it, don't know if that makes a difference.


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## jeffkrol (Jun 5, 2013)

Some, usually would be slightly higher w/ water. Your numbers certainly seem quite possible, and may be even on the low side than high (due to colored led's ). I crtainy would go on the "I have high light" philosophy..

You certainly need to raise or dim till you get a feel for what you and the tank can handle..


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## jeffkrol (Jun 5, 2013)

In your last thread, I stated "optics are unnecessary unless over 24" deep (or close).
I may consider just saying optics are unnecessary.. but you still need to determine that. 
Dim the light a bit and take a photo from the side. W/ some photo manipulation (or right off the camera) you will get profile of your light delivery..

Removing the optics may cut PAR in 1/2 @31", making it more manageable and better spread. Just a guess though..


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## houseofcards (Mar 21, 2009)

So if the tank has water in it, how do you measure the LUX with an iphone? Do you hold angle the phone don't toward the substrate of how it perpendicular to the bottom. Seems kinda sketchy.


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## joebob296 (Sep 30, 2016)

jeffkrol said:


> In your last thread, I stated "optics are unnecessary unless over 24" deep (or close).
> I may consider just saying optics are unnecessary.. but you still need to determine that.
> Dim the light a bit and take a photo from the side. W/ some photo manipulation (or right off the camera) you will get profile of your light delivery..
> 
> Removing the optics may cut PAR in 1/2 @31", making it more manageable and better spread. Just a guess though..


Thanks for the idea on taking a picture from the side. I'll have to do that when I get some time later tonight. Im sure there is some overlap in the center. Although, I took readings from all 4 corners, center left, center middle, center right. It was about 1000 lux less at the far corners of the tank. Even still, I'm sure I can even some of it out.



houseofcards said:


> So if the tank has water in it, how do you measure the LUX with an iphone? Do you hold angle the phone don't toward the substrate of how it perpendicular to the bottom. Seems kinda sketchy.


The tank is empty. There is no water in it. I just laid my phone on top of the substrate.


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## houseofcards (Mar 21, 2009)

joebob296 said:


> The tank is empty. There is no water in it. I just laid my phone on top of the substrate.


Yeah, I realize that, I was just curious if you can even get an "accurate" reading with water in the tank since you'd have to angle the phone down toward the substrate.


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## joebob296 (Sep 30, 2016)

houseofcards said:


> Yeah, I realize that, I was just curious if you can even get an "accurate" reading with water in the tank since you'd have to angle the phone down toward the substrate.


Ah, sorry about that then. Unless you have a waterproof case or something, I don't see a viable solution as to using a phone to measure lux.


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## joebob296 (Sep 30, 2016)

These are my lights at full power, I had taken this a few nights ago. I still need to take a dim picture from the side and move the lights around to give more even coverage. Not sure why the image rotated.


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## jeffkrol (Jun 5, 2013)

What is the height from the light to the tank upper rim?
For better f/b t/b coverage it should be about 15"
I assume it is currently about 7..

Adding 7 to the 31.. 38" measure Lux at that height..


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## joebob296 (Sep 30, 2016)

jeffkrol said:


> What is the height from the light to the tank upper rim?
> For better f/b t/b coverage it should be about 15"
> I assume it is currently about 7..
> 
> Adding 7 to the 31.. 38" measure Lux at that height..


Ok, I will do that, and measure again. I moved the lights down due the the amount of overspill I had when they were at 10" above the tank rim. I do have the capability to dim each channel individually. I'll be playing with them for a few days. I'm waiting for some responses on buying plants from fellow members, so I have plenty of time. I think I am going to make a chart of what height and what brightness settings equal certain PAR. That way when I decide to go for medium or high light plants I can adjust accordingly.


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## gus6464 (Dec 19, 2011)

houseofcards said:


> So if the tank has water in it, how do you measure the LUX with an iphone? Do you hold angle the phone don't toward the substrate of how it perpendicular to the bottom. Seems kinda sketchy.


You buy a waterproof case.


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## joebob296 (Sep 30, 2016)

jeffkrol said:


> Some, usually would be slightly higher w/ water. Your numbers certainly seem quite possible, and may be even on the low side than high (due to colored led's ). I crtainy would go on the "I have high light" philosophy..
> 
> You certainly need to raise or dim till you get a feel for what you and the tank can handle..


Well, the rabbit hole just got alot deeper. I just got 3 full 20lb C02 tanks from work for free. They are out of hydro testing but my local welding shop will still swap them out for an extra 15$ whenever there empty. I've been reading about pressurized C02 on here and am trying to decide if I should jump in head first.


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## Sean W. (Oct 12, 2013)

joebob296 said:


> Well, the rabbit hole just got alot deeper. I just got 3 full 20lb C02 tanks from work for free. They are out of hydro testing but my local welding shop will still swap them out for an extra 15$ whenever there empty. I've been reading about pressurized C02 on here and am trying to decide if I should jump in head first.


:bounce::bounce::bounce:


bahaha thats like 4 lifetimes worth of co2! LOL


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## Hoppy (Dec 24, 2005)

Sean W. said:


> bahaha thats like 4 lifetimes worth of co2! LOL


Or, it is like 8 hours of leakage when you have a serious leak.>


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## joebob296 (Sep 30, 2016)

Just wanted to say thank you for all the help fellow members gave me. This pretty much seals the deal with my lights. Now, onto C02 and stocking ideas.


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## Sean W. (Oct 12, 2013)

joebob296 said:


> Just wanted to say thank you for all the help fellow members gave me. This pretty much seals the deal with my lights. Now, onto C02 and stocking ideas.


It's really not that complicated... If you can plumb and prime canister filter, you can setup a pressurized co2 system.


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## joebob296 (Sep 30, 2016)

Sean W. said:


> It's really not that complicated... If you can plumb and prime canister filter, you can setup a pressurized co2 system.


Well I have Ehiem 2217 canister filter, so I can do inline C02 on the output of my filter. Just more investment cost.


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