Lux meters to check Led????

[Chris Harbaugh]

Would somebody please tell me what kind of Lux Meters are on the market so I can check my tanks Hydra 26 lights??

I have 4 Hydra 26hd's over my 125g (72×24×18) and I'm going to get me a 220g or larger tank by the end of the month and I'm burning up corals..acro's that is.. I need to check the lux measurements.

I have read all about PAR reading ect. Ect. Ect. And now after all the reading people are saying that Lux measurements are more important than just plan PAR and Amazon has a huge selection from cheap to expensive and I think it best is I can get some advice about the devices that people own that are actually proven to work. Thank you for the help.

 

[clsanchez77]

The two are not the same thing, even though related by physics. PAR is specific to photosynthetically available radiation. LUX is more specific to how humans perceive visible light. For your corals sake, PAR is "more important" but as far as your tank's appearance is concerned, LUX plays an important role. Our hobby has become obsessed over PAR and I do think LUX needs more consideration, but I would not consider one a replacement for the other.

 

[mcarroll]

Would somebody please tell me what kind of Lux Meters are on the market

You might want to check on some old posts on the #lux #meter tags.

To summarize some of those posts...

You can start with a FREE lux meter app for your smartphone. It'll help you to get familiar with using a light meter without spending any money. Sometimes it can take folks a few apps to find one that's calibrated right for their smartphone – it'll be obviously wrong if it's wrong. So it's the cheapest way to start, but not quite the best or simplest.

After that, then next logical option is a simple, handheld lux meter like the "LX-1010B" I have. I paid about $12 on ebay some years ago. I think you can get them quicker from Amazon and similar online outlets these days, but seems like they go for $15-$20.

I haven't had the need for more than that, but there are more upgrade options if you have find more needs than a basic meter will fill. For some examples between around $80 and $200....Milwaukee makes one with a waterproof probe, the Seneye has more functions than just light metering, a few vendors sell stand-alone PAR sensors....after that you're solidly over $200 and into the market for a standard PAR meter.

2¢

 

[smilereef2017]

Seneye reef monitor works fine for this application

 

[saltyfilmfolks]

I use a photographer's meter, it does footcandles and lux. Around the tank I use a $14 luxmeter from amazon. Look for one that is 100,000 or 200,000 lux maximum.
Milwaukee makes a submersible one for $75. The Seneye lux meter is not a cosine corrected light meter and the readings are quite different and noted lux/par conversion dont work with it.

Its not an imperative to know the lux of the tank its just an optional way to check you par settings if a par meter is not available. but I do recommend it to par meter users who are really interested in understanding light.
In short, lux is intensity, intensity + spectrum is PAR.

A basic lux/par conversion constant for led at a 1;1 ratio is 60. Ie 6000 lux = 100 par. as the color changes to a more blue spectrum the constant is higher 65-75.
A typical MH say 20k radium bulb is around 50 as a constant. (some much lower) so 6000 is 120 par
Most t5 fall much lower in the 40 range. 6000 lux=150 par

When doing lux par conversion on leds with wacky color setting from the internet rumor mill, I run the conversion at 60, 65, 70 and 75 to estimate the range I'm likely working in.

20,000lux/60=333 par 20,oo0lux/70=285 par etc.......................Btw, 20,000 lux / 50 =400.,,,,,,,,,,this is worthy of note, MH and T5 in general have more par with less intensity. most believe it is the opposite.

Another use of the lux meter is to have a store or manufactures turn it up to full power and test a 12in. you immediately see the the difference in intensity between models (ap700 a 80 for instance) and then know approx what it can deliver when selecting them for your tank.
You can also take it to the lfs like i do to see how much light they use over the frag tank. I can do it so fast they don't notice, but round here, they all know me so they don't mind.(and then use more light on their SPS tanks.)



@mcarroll I find it particularly interesting in the last 18 months, the large number of users and random questions pertaining to lux and par and the large number of users who now own lux meters and do the conversions.
After 3 years of flaming and debate, it appears, Two nerds can change the world.

 

[Chris Harbaugh]

I use a photographer's meter, it does footcandles and lux. Around the tank I use a $14 luxmeter from amazon. Look for one that is 100,000 or 200,000 lux maximum.
Milwaukee makes a submersible one for $75. The Seneye lux meter is not a cosine corrected light meter and the readings are quite different and noted lux/par conversion dont work with it.

Its not an imperative to know the lux of the tank its just an optional way to check you par settings if a par meter is not available. but I do recommend it to par meter users who are really interested in understanding light.
In short, lux is intensity, intensity + spectrum is PAR.

A basic lux/par conversion constant for led at a 1;1 ratio is 60. Ie 6000 lux = 100 par. as the color changes to a more blue spectrum the constant is higher 65-75.
A typical MH say 20k radium bulb is around 50 as a constant. (some much lower) so 6000 is 120 par
Most t5 fall much lower in the 40 range. 6000 lux=150 par

When doing lux par conversion on leds with wacky color setting from the internet rumor mill, I run the conversion at 60, 65, 70 and 75 to estimate the range I'm likely working in.

20,000lux/60=333 par 20,oo0lux/70=285 par etc.......................Btw, 20,000 lux / 50 =400.,,,,,,,,,,this is worthy of note, MH and T5 in general have more par with less intensity. most believe it is the opposite.

Another use of the lux meter is to have a store or manufactures turn it up to full power and test a 12in. you immediately see the the difference in intensity between models (ap700 a 80 for instance) and then know approx what it can deliver when selecting them for your tank.
You can also take it to the lfs like i do to see how much light they use over the frag tank. I can do it so fast they don't notice, but round here, they all know me so they don't mind.(and then use more light on their SPS tanks.)



@mcarroll I find it particularly interesting in the last 18 months, the large number of users and random questions pertaining to lux and par and the large number of users who now own lux meters and do the conversions.
After 3 years of flaming and debate, it appears, Two nerds can change the world.

You 2 nerds are... and it's appreciated..

 

[clsanchez77]

In short, lux is intensity, intensity + spectrum is PAR.

This is best shortest explanation I have ever seen for lux vs PAR

 

[saltyfilmfolks]

This is best shortest explanation I have ever seen for lux vs PAR

I've had some practice. ;Stig

Funny it has been so hotly debated isn't it?

A par meter is basically a lux meter. It has filters to only measure the intensity of specific parts of the spectrum in the light source.

 

[clsanchez77]

I've been around 20 years and have always been impressed with the stupidity that justifies a flaming debate LOL. My comments above regarding the Lux vs PAR meter was specifically because of my concerns regarding LEDs. I know there has been published conversion factors for MHs, VHO/HOs (although I always wondered about actinic skewing) for years now but I am not very confident in the conversion factors for LEDs. I admit it's not my specialty so I prefer to use a PAR meter; we have one we share in our local club. After reading this post though, I may go pick up a $20 lux meter and calculate the conversions on each color channel though now that I am next in line for the PAR meter.

 

[saltyfilmfolks]

but I am not very confident in the conversion factors for LEDs.

the difficulty actually comes from the lack of data(that what ive been collecting) , and the ability to keep changing spectrum in leds. Thus my recommendation on 60 at a 1:1 color ratio. Time and time again even on manufacturers specs it lines up almost exactly at 60. A mars aqua, actually comes in at 63.

So i'm fairly confident that any adjustment to the blue end results in a higher conversion number, also backed by Dana article on leds. Blue is a narrow band compared to the rest of the entire spectrum in the par computation.

The other neat trick with a par meter is, if your color setting are excellent, you can give them to a friend, meter lux at 12 in, and they can match the par pretty closely.

 

[Mark Gray]

Interesting guys following closely

 

[clsanchez77]

the difficulty actually comes from the lack of data(that what ive been collecting) , and the ability to keep changing spectrum in leds. Thus my recommendation on 60 at a 1:1 color ratio. Time and time again even on manufacturers specs it lines up almost exactly at 60. A mars aqua, actually comes in at 63.

So i'm fairly confident that any adjustment to the blue end results in a higher conversion number, also backed by Dana article on leds. Blue is a narrow band compared to the rest of the entire spectrum in the par computation.

The other neat trick with a par meter is, if your color setting are excellent, you can give them to a friend, meter lux at 12 in, and they can match the par pretty closely.

What I am interested in is how does the introduction of UV and violet change this? They will contribute very little in the way of Lux but in theory should contribute to PAR, at least the Violets. I also have greens (that I currently have off) that will contribute greatly to LUX but have little impact (in theory) on PAR. Now you have peaked my interest in what was otherwise going to be just a to-do to check off my list. I will order the Lux meter and post my findings. The PAR meter should be here by the end of the week.

 

[saltyfilmfolks]

What I am interested in is how does the introduction of UV and violet change this? They will contribute very little in the way of Lux but in theory should contribute to PAR, at least the Violets. I also have greens (that I currently have off) that will contribute greatly to LUX but have little impact (in theory) on PAR. Now you have peaked my interest in what was otherwise going to be just a to-do to check off my list. I will order the Lux meter and post my findings. The PAR meter should be here by the end of the week.

Yes it does but the uv is not read well by a par meter either. Color mixes even when read by a par meter are kinda inaccurate in a way, you need to use a spectrometer to adjust those levels precisely in conjunction with the paper meter, and then also know how much of each Nm wavlength you want depending on what corals you have

 

[clsanchez77]

Yes it does but the uv is not read well by a par meter either. Color mixes even when read by a par meter are kinda inaccurate in a way, you need to use a spectrometer to adjust those levels precisely in conjunction with the *PAR meter, and then also know how much of each Nm wavlength you want depending on what corals you have

Ok, well that will be above my pay grade as I don't have access to a spectrometer.

 

[saltyfilmfolks]

Ok, well that will be above my pay grade as I don't have access to a spectrometer.

Lol. Thus I question the chasing of par quite often. Save to set it and know the range were using, And for most average users I suggest the Lux meter.

 

[dacianb]

The sensitivity of the human eye to light of a certain intensity varies strongly over the wavelength range between 380 and 800 nm. Under daylight conditions, the average normal sighted human eye is most sensitive at a wavelength of 555 nm, resulting in the fact that green light at this wavelength produces the impression of highest “brightness” when compared to light at other wavelengths. The spectral sensitivity function of the average human eye under daylight conditions (photopic vision) is defined by the CIE spectral luminous efficiency function V(λ). Only in very rare cases, the spectral sensitivity of the human eye under dark adapted conditions (scotopic vision), defined by the spectral luminous efficiency function V’(ë), becomes technically relevant. By convention, these sensitivity functions are normalized to a value of 1 in their maximum.

As an example, the photopic sensitivity of the human eye to monochromatic light at 490 nm amounts to 20% of its sensitivity at 555 nm. As a consequence, when a source of monochromatic light at 490 nm emits five times as much power (expressed in watts) than an otherwise identical source of monochromatic light at 555 nm, both sources produce the impression of same “brightness” to the human eye.

This is what luxmeters measure actually - exactly what human eye can see.
For example if I use tons of violets and deep blue leds on my tank luxmeter will measure next to nothing, but PAR and radiometric power will be more than enough to burn everything in tank; If will use only white and green leds over my tank, LUX values will be sky-high, but PAR and radiometric power really low.

Just my 5 cent opinion

 

[saltyfilmfolks]

The sensitivity of the human eye to light of a certain intensity varies strongly over the wavelength range between 380 and 800 nm. Under daylight conditions, the average normal sighted human eye is most sensitive at a wavelength of 555 nm, resulting in the fact that green light at this wavelength produces the impression of highest “brightness” when compared to light at other wavelengths. The spectral sensitivity function of the average human eye under daylight conditions (photopic vision) is defined by the CIE spectral luminous efficiency function V(λ). Only in very rare cases, the spectral sensitivity of the human eye under dark adapted conditions (scotopic vision), defined by the spectral luminous efficiency function V’(ë), becomes technically relevant. By convention, these sensitivity functions are normalized to a value of 1 in their maximum.

As an example, the photopic sensitivity of the human eye to monochromatic light at 490 nm amounts to 20% of its sensitivity at 555 nm. As a consequence, when a source of monochromatic light at 490 nm emits five times as much power (expressed in watts) than an otherwise identical source of monochromatic light at 555 nm, both sources produce the impression of same “brightness” to the human eye.

This is what luxmeters measure actually - exactly what human eye can see.
For example if I use tons of violets and deep blue leds on my tank luxmeter will measure next to nothing, but PAR and radiometric power will be more than enough to burn everything in tank; If will use only white and green leds over my tank, LUX values will be sky-high, but PAR and radiometric power really low.

Just my 5 cent opinion

Your correct. Kinda, it goes deeper.
And keep in mind what I mentioned earlier.
A par meter is a lux meter. Kinda.
http://www.advancedaquarist.com/2013/2/equipment

 

[dacianb]

from a reason I cannot upload any pics on this forum, but still... human eye sensitivity have a shape of a "bell" from 400 to 700 nm with peak at 555 (green).
Parmeters use same spectral range (400-700nm) but absolutely flat curve. Basically they measure radiometric power in the 400-700 nm range;

the best way to correlate LEDs LUX with PAR is to approximate each color differently - use a specific correction for violets, other for deep-blue, other for white;
Otherwise, any method proposed may work on certain type of light with a certain mix, but never on all combinations on market today.
On my tank I have ratio of 3 to 1 UV+BLUE to whites. I tried and my lux level is tiny, but still burned few sps over time

I am optical engineer as profession and in this area we use only one way to measure the light - radiometric power. All other numbers you see are artificial curves applied to those basic, accurate measurements - PAR, Lux, Lm, and whatever

 

[mcarroll]

The wikipedia page on luminosity has a graph of the function.....that's where I realized that blue is part of the function.

I'd be curious to see how well the $12 lux meters were use actually map to the luminosity function......I know my meter seems to be plenty sensitive to 450nm LED's when I test them compared to Cool Whites. (I suspect it's more sensitive than "it should be" to blue.)

@mcarroll I find it particularly interesting in the last 18 months, the large number of users and random questions pertaining to lux and par and the large number of users who now own lux meters and do the conversions.
After 3 years of flaming and debate, it appears, Two nerds can change the world.

Well said! I got a funny PM on the subject from @john.m.cole3 just the other day in fact.

#lux #meter

 

[saltyfilmfolks]

from a reason I cannot upload any pics on this forum, but still... human eye sensitivity have a shape of a "bell" from 400 to 700 nm with peak at 555 (green).
Parmeters use same spectral range (400-700nm) but absolutely flat curve. Basically they measure radiometric power in the 400-700 nm range;

the best way to correlate LEDs LUX with PAR is to approximate each color differently - use a specific correction for violets, other for deep-blue, other for white;
Otherwise, any method proposed may work on certain type of light with a certain mix, but never on all combinations on market today.
On my tank I have ratio of 3 to 1 UV+BLUE to whites. I tried and my lux level is tiny, but still burned few sps over time

I am optical engineer as profession and in this area we use only one way to measure the light - radiometric power. All other numbers you see are artificial curves applied to those basic, accurate measurements - PAR, Lux, Lm, and whatever

High alk, and low nutrints will also burn tips.
And by tiny Lux , can you be specific.
And yes.
Nobody uses a spectrometer on their tanks. Except maybe me.

For the laymen or hobbiest . Lux and par and more than enough.
I find it odd your post seems to theow doubts on both.