# Effects on PAR - Air and Water



## Nathaniel Whiteside (28 Oct 2013)

Hey guys,

Does anybody know a correlation between the PAR measurement of a light from a specific distance and then the same distance but filled with water? 

So my tank is 18" deep, but lights may sit another 6" above water.  

Here's the Info page and mines the 160w. 

R420r LED Lighting System

Is there a simple measurement eg. Drypar divided by ...? 

Cheers,


----------



## Yo-han (28 Oct 2013)

I think this is impossible. Because it depends on how clear the water is (suspended particles, tannins etc.), surface scum, even water movement on the surface.

But I've seen the Razor in real life last week, it does look bad *ss! I think the designer came from a computer parts designing company


----------



## Nathaniel Whiteside (28 Oct 2013)

Yo-han said:


> I think this is impossible. Because it depends on how clear the water is (suspended particles, tannins etc.), surface scum, even water movement on the surface.
> 
> But I've seen the Razor in real life last week, it does look bad *ss! I think the designer came from a computer parts designing company



Ha, I thought this would be the response.
There must be a 'standard' for 100% clarity water.

It's far beyond my knowledge.

How did you find the light Yo-Han? Was it bright? Mines arriving tomorrow


----------



## Yo-han (28 Oct 2013)

I saw the 120W 16.000K version. This one was already bright, I expect the 8.000K (I guess that is the one you'll get) to be even brighter.

About the PAR. Even with 100% clear water and no surface movement, I think it would still be impossible. It would depend on things like angle and light color. Using 20.000K you might get most of the light on the bottom, Using red light, you may loose quite a few percent. But I've seen postst from people measuring just above and below the surface, so perhaps you can calculate a rough number out of that...


----------



## George Farmer (28 Oct 2013)

They are very bright, as you'd expect with 160w of LED. You will never need to worry about not enough light.  On the contrary in fact... I guess at the substrate you'd get PAR 150+ in 90x45x45, which calls for monumental level of CO2 and nutrient management, and maintenance.

Gary Nelson is using one over his lovely Eruption scape.

'Eruption' | UK Aquatic Plant Society

Have fun!


----------



## nphsmith (28 Oct 2013)

George Farmer said:


> They are very bright, as you'd expect with 160w of LED. You will never need to worry about not enough light. On the contrary in fact... I guess at the substrate you'd get PAR 150+ in 90x45x45, which calls for monumental level of CO2 and nutrient management, and maintenance.


 
George,
I have a remarkably similar query elsewhere, but this one came first so will tag along - I'm planning to have light 18"/45cm above 20"/50cm of water. Does the above advise still apply to a Razor?


----------



## George Farmer (28 Oct 2013)

Short answer - yes! 

You'll lose light through the air - at 18" on this unit it won't matter though.


----------



## BigTom (28 Oct 2013)

The accepted wisdom over on some of the US forums seems to be that water has a pretty negligible effect on PAR compared to air, and that in some cases it may even increase PAR (diffraction? Lensing? Not sure why). I haven't seen whatever data they're basing that off though.


----------



## George Farmer (28 Oct 2013)

I tend to agree with that from my own PAR readings in and out of water.


----------



## Nathaniel Whiteside (28 Oct 2013)

Thanks for your replies guys.

I was aware they were going to be bright, just wanted to put a figure on it  really. I thought there would be a fairly substantial drop in PAR through water though. 

You learn something


----------



## Nathaniel Whiteside (29 Oct 2013)

Okay, having burnt my retinas completely out my face...
I can confirm, these lights are bright.


----------



## nphsmith (29 Oct 2013)

Nathaniel Whiteside said:


> Okay, having burnt my retinas completely out my face...
> I can confirm, these lights are bright.


 You probably aren't now able to see the lawyer's note, which is along the lines of "If you blind yourself, tough"


----------



## Nathaniel Whiteside (29 Oct 2013)

Fair reflection of how it looks in the flesh. 

My eyes hurt.


----------



## nphsmith (29 Oct 2013)

What's the control like? Difference between A & B channels?


----------



## nphsmith (29 Oct 2013)

I suppose I'm trying to work out if they can sensibly be used for moonlights?


----------



## Nathaniel Whiteside (29 Oct 2013)

nphsmith said:


> What's the control like? Difference between A & B channels?





nphsmith said:


> I suppose I'm trying to work out if they can sensibly be used for moonlights?



Hey,

One channel has Warm white(3,000k). and daylight (8,000k) colours, the other has Daylight and Blue (445-465nm)

So one channel can be used more than the other. If the A channel is used at 100% and the B channel at 0% the look is very warm and orangey yellow like a sunrise, which you can programme.

The other way round gives the moonlight look, and on 1% it gives a very dim blue light as if simulating moonlight on the tank, which I can see myself using.

Inbetween you can ramp up and down and change spectrum ( warmer by keeping the A channel higher than b channel, or a more edgy stark white with the B channel higher). 

I love the spectrum change it gives. Been playing with it all night lol. What a kid. 

Cheers,
N


----------



## nphsmith (30 Oct 2013)

Nathaniel Whiteside said:


> Hey,
> 
> One channel has Warm white(3,000k). and daylight (8,000k) colours, the other has Daylight and Blue (445-465nm)
> 
> ...


 
Excellent. And how far above the tank do the legs take it?


----------



## Troglodyte (17 Nov 2013)

Nathaniel,
I have to agree with BigTom and George. PAR levels can be increased in water due to the reasons BigTom stated. Measurements in air are a poor substitute for water measurements. Refraction off water movement and tank surfaces add to more light being reflected back into the aquarium where it would have been lost.
You may also be able to see this in glitter lighting within the water, where light is being reflected.


----------



## sanj (17 Nov 2013)

Nathaniel,

I have the 120w over a 60x45x45cm. I also have a PAR meter! 

Like George says, these are powerful and my concern would be too much light rather than being enough. I didnt like the legs and also felt it didnt spread the light evenly enough, but if your tank is narrower that should be less of an issue. Mine average around 50% of the total output and I am getting 30+ PAR at the substrate. They are suspended 10" above the water surface.


----------



## Nathaniel Whiteside (17 Nov 2013)

nphsmith said:


> Excellent. And how far above the tank do the legs take it?


 

Hey mate, I think you have received yours now, but in case not, they're about 6" above the rim of my tank.
Sorry about the late reply.




Troglodyte said:


> Nathaniel,
> 
> I have to agree with BigTom and George. PAR levels can be increased in water due to the reasons BigTom stated. Measurements in air are a poor substitute for water measurements. Refraction off water movement and tank surfaces add to more light being reflected back into the aquarium where it would have been lost.
> 
> You may also be able to see this in glitter lighting within the water, where light is being reflected.


 
Hello Trog,
Thanks for your information, I now see how water movement can play a role in intensifying the light.



sanj said:


> Nathaniel,
> 
> I have the 120w over a 60x45x45cm. I also have a PAR meter!
> 
> Like George says, these are powerful and my concern would be too much light rather than being enough. I didnt like the legs and also felt it didnt spread the light evenly enough, but if your tank is narrower that should be less of an issue. Mine average around 50% of the total output and I am getting 30+ PAR at the substrate. They are suspended 10" above the water surface.


 
Hey Sanj,
Yeah! these lights are definitely BRIGHT! Ive never used MH or the like, but apparently these 160W units outperform 400W Bulbs.
My tank is an ADA 90p (90x45x45), but luckily spreads almost into all four corners. The legs aren't that pretty, I'll admit. Though a lot better than TMC's MMS Bracket. 
Once my cabinet is in order (currently building it, Waiting for Veneer) and I have a position that suits, I will probably drill the ceiling, Because the R420R unit itself without arms attached looks very Sleek and almost 'Stealthy'.

Cheers all,
Nathaniel


----------

