Mirror - Page 3

reefburnaby · #21 02-14-2002, 04:02 AM

Hi,

IMHO, it really does matter if the light is distributed using a specular reflector or a diffusive reflector. The main idea is to get light from the bulb in to the tank and both do the job. You'll just have to design the reflector to do the job correctly. In other words, a specular reflector doesn't look exactly the same as a diffuse reflector.

So, in terms of white vs shiny, white and shiny do a very good job at reflecting visible light. The difference between white and shiny is that shiny reflects other types of waves (like gamma waves, x-rays, infra-red and etc) and white doesn't do a very good job at that -- hence white paint's high emmisitivity. Emmisitivity is a measure of how much electromagnetic waves a material will absorb -- visible lilght is only a small band in the electromagnetic spectrum. Since our application involves concentrating visible light in to our reefs, then shiny and white should preform similarly (with the upper hand to shiny...since 100% pure white and mirror flat surface is hard to obtain with paint).

Specular and diffuse refectors have their problems. Diffuse refectors tend to spread their light even across the reef -- this may be problematic if you are try to raise light loving corals. Specular reflectors tend to concentrate their light on to specific bands within the reef. IMHO, this can be problematic because certain parts of the reef aren't well lit and some are too well lit -- so coral placement will be key.

One point that I haven't seen in papers is that white reflectors do get hotter than shiny ones. This is because white does not reflect infra-red very well. This may be a good thing since we can remove the heat from the white reflector with fans. On the other hand, a shiny reflector would deflect the IR waves in to the water and warm it up. It is much more difficult to remove the heat from the water...

So...there's my take. Both methods are fine. The design of the reflector must take in to account of the advantages and disadvantages of each method.

Hope that helps.

- Victor.

[ 14 February 2002: Message edited by: reefburnaby ]

[ 14 February 2002: Message edited by: reefburnaby ]

Reefmaster · #22 02-14-2002, 04:26 AM

so i'm curious victor, is it likely white reflectors are also absrobing a bunch of the longer wl's as well? i don't think i know why white would absorb IR but not UV. simply a function of the wl?
either way this thread has gotten me to thinking i want a new reflective media in our hood.
shane

reefburnaby · #23 02-14-2002, 04:43 AM

Shane,

White paint have been engineered to reflect all visible light -- hence the colour white. However, each blend/brand of white paint have no guarantees as to what it will do to IR, UV and other waves -- unlike shiny metals (almost guaranteed). Without being specifically engineered to reflect IR or UV, the paint is mostly likely going to absorb all or some of it (engineers/chemists tend not to overdesign [img]images/smiles/icon_wink.gif[/img] it is a hard enough problem as it is )

Hope that helps.

- Victor.

[ 14 February 2002: Message edited by: reefburnaby ]

Canadian · #24 02-14-2002, 12:46 PM

Just an FYI, using fans to cool the air temperature in your hood (eg. blowing fans at your reflector or lamp) as opposed to using fans blowing onto the water's surface to effectively control temp is not one of the best ideas. Cooling the air temperature around the lamp will cause a shift in the spectrum emitted by the lamp. Everyone hates 5500K lamps because they're too yellow, so why would you blow air at your reflector or 6500K lamp therefore causing the color temperature to decrease if you could avoid this arrangement?

Those who actually have experience with MH lighting (incl. HQI) over their reef tanks know that they purchased the lamps and ballasts in an attempt to maximize intensity. Making any effort to diffuse that intensity in an effort to get even distrubution of a lower intensity is clearly counterproductive if you intend to keep light-loving corals alive and healthy. Your only recourse should you choose to diffuse your point source lighting (still can't figure out why on earth you'd want to do that in your reef tank) would be to purchase additional lamps and ballasts in an attempt to compensate for the lost intensity -- go nuts if you've got the money to waste.

I'd like someone to point out to me what the problems with focusing specific bands of higher intensity artificial light into your reef tank are. Before these higher intensity point source lamps were available hobbyists struggled to keep SPS, Tridacnids, etc. alive with diffused light sources, let alone thriving. "Too well lit"? What is it that we're attempting to replicate? The sun? Is the sun overlighting the ocean?

If you want to have evenly distributed light over the entire surface area of your aquarium while also having sufficient intensity to keep light loving corals, put more lamps over your tank.

[ 14 February 2002: Message edited by: Canadian ]

Aquattro · #25 02-14-2002, 01:45 PM

<blockquote>quote:<hr>this arrangement?

I'd like someone to point out to me what the problems with focusing specific bands of higher intensity artificial light into your reef tank are.

[ 14 February 2002: Message edited by: Canadian ][/QB]<hr></blockquote>

Andrew, as I'm sure you are aware, glitter lines from MH lighting are speculated (proven?) to enhance SPS growth due to the focused intensity of the light. This confirms that focused light not only isn't bad, but probably benificial. I have to agree that after spending all the dollars to install MH lighting, the last thing I want to do is diffuse it!!

DJ88 · #26 02-14-2002, 07:23 PM

<blockquote>quote:<hr>that is if the corals want more light. However, if your precious SPS coral sits between a bright band and a no/low light band (assuming no glittering), then half of you SPS is not doing well...and the other is doing very well. In other words, there is a chance that half the SPS will actually starve. I know this is an extreme example and it rarely happens because....
<hr></blockquote>

Won't happen.. Have you ever had the surface of your tank perfectly calm ALL the time? I haven't, Not with proper circulation in your tank you won't. Those "glitter" bands you see will move. Show me a tank where they don't move and I will show you a tank with not enough circulation.

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As for the cooling thing...we could try blowing at the the reflector from side, but not at the bulb.

Why? Blow it at the waters surface and you will get the best cooling results through evaporation. Those running MH's or any high heat lighting in your hood will find this out. The amount of cooling you will get through cooling the reflector is so minimal in comparison to what you get from evaporation it is a waste of time and energy IMO IME. I have tried it. I am running the fans to blow across the H2O and will in any future systems. I recommend it to anyone running MH or experiencing heat problems in a tank.

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Those who actually have experience with MH lighting (incl. HQI) over their reef tanks know that they purchased the lamps and ballasts in an attempt to maximize intensity.

Yup. As I measure it on my new little light meter my MH produces about 20,000 lux(quick measurement). When I read direct sunlight it hits many, many, many times this amount. I just measured it at 62,000 lux outside with clouds and smog. That is three times the amount of light outside with clouds than my MH produces at 12" away. Why would you want to diffuse it and make it less than that? The flourescent lamps in my elevator produce 300 lux for a reference point for those who don't have MH or have never ran a MH.

<blockquote>quote

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Making any effort to diffuse that intensity in an effort to get even distrubution of a lower intensity is clearly counterproductive if you intend to keep light-loving corals alive and healthy.

For those who still want to do this, read my last statement. We are many times BELOW what the sun puts out into the ocean. WHY???? would you want to diffuse it????? You are putting your corals at risk. In effect you are giving them LESS chance at being healthy.

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Your only recourse should you choose to diffuse your point source lighting (still can't figure out why on earth you'd want to do that in your reef tank) would be to purchase additional lamps and ballasts in an attempt to compensate for the lost intensity -- go nuts if you've got the money to waste.

I can't understand the point of diffusing something that is supposed to provide point source lighting???? Agree 100% here.

If you want to diffuse your lighting and then compensate with more bulbs or lamps go for it. Most here are trying to save money where they can by DIY'ing the ballasts etc. You are shooting yourself in the foot by reducing what those lights put out with diffusing IMO.

[ 14 February 2002: Message edited by: DJ88 ]

Troy F · #27 02-14-2002, 07:59 PM

Good post Darren.

One thing that I came upon in my reefboard wanderings was Jerel's lighting schedule. He runs his MH in short bursts and is experimenting with increased growth with less light. Basically, he points to the amount of energy a coral must use to protect itself from the UV radiation and is trying to find the line of balance where there is actually too much light in regards to growth. The point where the coral begins expending more energy protecting itself than growing. This would be an expensive endeavour however, as you would seriously jeoprodize the life of the bulb. He offsets this by using electronic ballasts and being rich (apparently). I realize this is a little off topic. My reason for posting this is that our closed systems don't mirror [img]images/smiles/icon_smile.gif[/img] the real world for a number of reasons.

One_Divided · #28 02-14-2002, 10:03 PM

I just had an idea.. In our reef tanks, our bulbs are totally stationary. Aside from the shimmering cuased by halides, there are without a question, spots (cuased by shadows) that would end up getting very little light compared to other spots. In nature the light source (the sun Duuhh) rotates and therefor would light most corals from almost every angle possible over the course of a day. Has anyone ever thought of the idea of light movement? It could be tricky and expensive, but if done in the right way might actually save money. If a bulb could start on one end of the tank and end up at the other side by the end of the day then most areas of the tank would be hit by light. For example, using 1 1000w halide instead of 3 400ws.

I don't know, I could just be talking out of my a$$, but it's just an idea.. Now the hard part is inventing the machine that moves the bulb from side to side.. How about roatating in an oval? [img]images/smiles/icon_eek.gif[/img]

StirCrazy · #29 02-14-2002, 10:13 PM

this is something that a lot of fanatics do in planted fresh water tanks Adam, I was at a web page whare a guy has a 400 watt MH bulb slowly start at one side of his tank and move across over the course of a day to the other side of the tank on a motorized track. he also had hidden floresent lights for ambiant (sp) light.
If I can remember the page I will get you the link.

Steve

Canadian · #30 02-14-2002, 10:16 PM

Adam, "they" make them. Lighting tracks of the type you describe are used in hydroponics and they have been used in reef aquarium applications as well. The inherent problems with them are: huge cost, size, and the potential for any mechanized device like that to seize up when mounted in close proximity to the evaporated water coming from an aquarium (among other things).

But if you're really interested in implementing the idea take a look on RC and reefs.org; there have been a few people with "high end" set ups who have incorporated that kind of an idea into their setups.