Mirror

[terryp01]

Language, please.

[DJ88]

Chris,

If I remember the numbers right I believe that a proper parabolic reflector will increase the light going into the tank by 75% or something liek that. Troy started a thread on this board if I remember right where the numbers are stated. An optimal reflector at J&L is only $46 plus tax. or something like that.

I have a white painted hood and can't have a reflector due to the size of my lid. I will be putting a proper reflector in the 45 when it is up and running. I am positive that I am losing a huge amount of light due to my white hood. [img]images/smiles/icon_sad.gif[/img]

[reefburnaby]

Hi,

I am not sure, but I seem to recall Sanjay saying that a spider reflector makes a 175W MH as bright as a 250W MH.

- Victor.

[Gordoe]

I'm almost afraid to post, naaahhh!

You need to keep a few things in mind;

1. You want both visible and "invisble light" reflected.

2. Several things can happen to the light that interacts with a surface. It can be reflected by the surface, just like light on a mirror(Reflected). It can be absorbed by the surface, in which case it causes a change in the temperature(Absorbed or Emitted). In some cases the light can be transmitted through the surface(Transmitted).

R+E+T=1

The reflectors we use have a T of 0. Mirrors that get hot do not have a refectivity of 1, therefore they are absorbing some light.

Polished aluminum has an emissivity(absorption)of 0.05. Paint has an emissivity of about 0.9.

Go with polished aluminum to reflect your lights. If you want to diffuse the light get hammertone, or parabolic.

[One_Divided]

Put an "IME", "IMO" or an "I read somewhere that.." and everyone gets along..

I like to have ideas on reefkeeping and keep my beliefs to the scientific facts. If you don't know for certain that something is a fact, then don't state it as if it is one.

I'd like to add on this and the other current lighting post in this forum.. IME, I have used milar for the whole inside of my hood and after about 9 months, some of the silver just sort of started falling off and left behind clear plastic. Now this worries me, becuase I don't know where that silver stuff went.. I have a feeling it may have corroded by the salt.
[img]images/smiles/icon_confused.gif[/img] So I'd say if you are going to use milar, don't cheap out.. Get the highest end you can get.. I think that lighting is an essencial part of this hobby that people too often try to dodge.

[StirCrazy]

Ok I just re read the posts here and I see what caused all this .. I assumed that beacuse a miror was wanted that were were talking about flat reflectors only (my mistake) yes if you can go with a parabolic then that is the best but my opinion was on using a flat reflector on top of your light, and in "My Opinion" I would rather have a reflector that difuesed a point sourse light than a spectral reflector in this instance. the reason for this is if you have hot spots you get burnt plants maybe this is not as important in a reef but, I have been playing with planted freshwater tanks for about 22 years and making my own lights for the last 16.

a good article to read with actual studies on different reflector material is by RICHARD HARKER

another statment by Tom Miller

"Glossy white reflectors are also quite effective. A very glossy enameled white reflector can come very close to the same reflectivity of a good mirrored reflector - such as polished and anodized aluminum. Flat white reflectors are less reflective than glossy white reflectors. Non-mirrored aluminum reflectors likewise are not as reflective as highly polished mirrored aluminum. Aluminum is very reflective when polished and protected from corrosion. Aluminum is a very common, less expensive, and high reflectivity coating used on many astronomical telescope mirrors as well."

so I apolagize for any wrong info that might have been derived from my post.

Steve

[Shadetree]

I cannot remember where I read it or even when, I just know that it has been stated that the painted white hood is not much better than NO reflector or paint at all.

The graph, courtesy of Richard Harker, can be found in context in the referenced thread above.
This graph shows that it reflects pretty much NOTHING. The second graph goes on to show that it does a little bit to diffuse the light, but if it doesn't reflect any light what good is that [img]images/smiles/icon_rolleyes.gif[/img] . I think your second quote is out to lunch, or completely unsubstantiated. Remember the above is glossy painted aluminum flashing, I can only imagine painted wood would be worse. A guy on RC, in this thread http://www.reefcentral.com/vbulletin...threadid=55527 found that he got almost 1/3 MORE light with proper reflectors. If you are going to spend the money on halide lighting, I do not see the point of skimping on a quality reflector (DIY is not skimping IF it is made from the proper material).

Scott

[StirCrazy]

here is the other one Shadetree,


this is what I was talking about.. by using white paint or hammer tone or plain aluminum flashing you will not get as much light as using a miror type but you will be able to get a more even and consistant lighting throughout the tank.. but in the same tolken you will not get that high light area whare your SPS will thrive while the rest of the tank is not quite as intence. it is a trade off for what you want I guess, I personaly am using a spectral reflector on my floressent type bulbs and I will use hammer tone on my MH when I get them to TRY get the same intensity everywhare in the tank.

Steve

[Shadetree]

Steve,

What good does diffused light do if it is not reflected back into the tank?

Scott

[DJ88]

Steve,

You lost me..

Why would you want to diffuse the light going into your tank? Any of it. Whether it is NO, VHO, PC or MH??? What are you worried about by having those areas of high intensity where light is stongly focused? Once you sit down for a long period of time and can watch corals and how they react to this lighting you will se why the focused areas IMO are a good thing. We are not even close to re creating natural light levels produced by the sun in our tanks. Not even close. I'd say about 1/10th of the levels. SO any area where focusing happens is a good thing IMO.

Keep one thing in mind through all of this. <ul type="square">[*]Diffusing results in drastic losses in lighting strength in your tank.[*]Less strength means less penetration into your water.[*]Less penetration means a higher depth for light needing corals where they can be kept into your tank(Corals need to be near the surface)[*]Decrease the light being sent to the corals and you decrease the chances of survival.[*]Period. [/list:u:4342bfe463]

It is the intensity of a MH that allows us as reefkeepers to have many of the coral species in our tanks that we are able to. By putting something in your tank that diffuses the light you have defeated the purpose of maximizing your lighting all together IMO.

Diffusing the light is in effect decreasing it's intensity. Once you do that you have again defeated the purpose behind having intense lighting in your tank. It is only the intesnse lighting of say a MH bulb that reaches the depths of most tanks we use today. NO lighting loses its strength on a massive scale as you go into the water. VHO's & PC's are next for penetration then MH's in it's various forms. By diffusing the light you are reducing how deep the light your corals need so crucially penetrates. A mirrored of polished aluminum reflector is there to get all the light that is being sent in directions other than into your tank and refelcting it back where you want it.

Look at this drawing:


This is with no reflector. Red lines are full strentgh light beams going into the tank. Orange are diffused light(lower strength). Due to waters nature only light that is emitted from the bulb that results in an angle less that waters critical angle(drawing two) will actually penetrate at full stregth. Anything that doesn't make it within this angle is reflected. losing intensity, diffusing in other words. The light that is sent up to the lid loses strength as it is reflected by white paint and is then useless IMO. Unless it is actually reflected a part of that light is lost due to absorption or diffusion. A big part.



When light hits a different medium than air such as water it needs to do so at a certain angle or LESS for it to penetrate. If it is greater than that angle it gets reflected. Once you start reflecting light off of surfaces you lose intensity.

Here is where the parabolic reflector comes in. It gathers the light being emitted by the bulb and sends it in the proper direction to allow for maximum penetration of the water by the maximum amount of emitted light.



Personally I'd put reflectors over every single thing I could in my tank. I want every single bit of effective light to go into the tank. If I could go mirrored I would. But I can't. So Polished metal it is.

[ 14 February 2002: Message edited by: DJ88 ]</p>