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>