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Old 03/15/2005, 03:29 PM   #1
WaterKeeper
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Lightbulb Alright Newbie; Let's shed some light on this subject.

I've covered this topic before but it appears that some of you newbies weren't listening or so dense it didn't sink in the first time. So Listen up!!!

One of the biggest investments you will be making in setting up a new tank is the lighting. There are all sorts of posts here on RC debating which lighting is best. Obviously, if the author of these posts sold his wife's kidney and a lung to buy the ultra-sun, super blue metal halides he is going to make a pretty good case why those lights outshine all the others. You hear that xyz lighting is the only type lighting that will assure success in your reef tank. Let's try to set the record straight here and look a little deeper into lighting.

First, for those of you who fell asleep when they talked about Thomas A. Edison in class, let's get the technical part out of the way. In current reef setup there are two main classes of lighting, fluorescent and metal halide.

Fluorescent has some subsets such as PC's, power compacts, but they are in fact fluorescents going under an assumed name. A fluorescent is just a hollow tube with a filament at each end. The tube is filled with an inert gas, argon or krypton, and there is a very small amount of metallic mercury in the tube. The glass wall of that tube is coated with a blend of chemicals known as phosphors. There are many types of phosphors and, since their chemistry is on a need to know basis, you don't need to know it. In operation a high voltage is momentarily applied to the filaments. The tiny bit of mercury inside the tube gives off some mercury vapor. This makes the inside of the tube conductive and when the high voltage is applied a current flows down the length of the tube between the filaments. After the lamp starts it warms and more and more mercury is vaporized allowing more current to flow. Shortly after starting the resistance in the tube falls like a rock and the lamp would burn brighter and brighter. Finally so much current would flow that the lamp would wink itself out like a supernova and fail.

Enter the ballast. Most of you have seen a ballast. It usually looks like a brick inside the fixture. A ballast serves two purposes. It provides that extra voltage kick to start the lamp and it also limits the amount of current the lamp can draw. This latter function is why the lamp does not burn out the first time it is put in use. Now ballasts come in two major flavors. Magnetic coil ballasts, which work like a current limiting transformer, and electronic ballasts, that are a type of silicon controlled rectifier. Both keep current levels from exceeding the limit for that bulb. The cheaper, magnetic ballast does so mainly by dissipating the excess current as heat. This is not very efficient as the ballast itself adds wattage above and beyond that consumed by the lamps. Electronic ballasts limit the current by solid-state electronics that don't lose energy as heat. Here the ballasts and lamps usually draw no more wattage than the lamp alone saving some money. They also produce a higher frequency current going to the lamp. This eliminates the flicker affect that is associated with lamps run on magnetic ballasts. Electronic run much cooler and they can run multiple combinations of lights where a magnetic needs to be matched to the lights in use.

The main drawback is cost. Electronic ballasts costs much more than a magnetic. Also, like the electronics in your computer they don't do well with voltage spikes. A failed filament shorting out can not only end the life of the lamp but take the electronic ballast out too. If your kid is building a thermo nuclear devise for the school science fair the accidental detonation, and resulting electro-magnetic pulse, will fry the circuits in an electronic. I can see the management at Icecap yelling to R&D, That darn WaterKeeper is stirring things up again. Quick, get a nuke and see if our ballasts fail.

The lamp is now fired and the mercury vapor is giving off photons and electrons. Problem is that most of it is in the lower wavelengths that don't supply much visible light. That emitted radiation strikes the phosphors that coat the tube and they begin to glow much brighter than the mercury discharge. That glow is usable light and our fluorescent is now functioning in its normal manner. When fluorescents first came out they used single phosphors that emitted in the red-green regions of the spectrum. Now they use all sorts of blends that allow them to produce light over the entire spectrum.

So far I have not said much about metal halides. That is because MH lights work almost the same as a fluorescent. A high voltage is applied to start an arc across the filaments. This in turn causes the gas inside the lamp to become hot and glow. The gas would become hotter and brighter as the current increased. In fact, so hot that the lamp tube would melt if things continued without limit. Once again, a ballast steps in and limits the current that the lamp will draw and prevents burnout. The main difference between the two systems is that the fluorescents depend on the phosphors to provide secondary radiation and usable light while the MH is more like an incandescent using a hot gas cloud to provide the light.

Ballasts for a MH lamp will not run fluorescents and vice versa. For one the starting circuits differ. A MH may have three elements with one being an igniter filament or some with only two that use what is called pulse start. If you have a hood with both MH and say VHO you need separate ballasts for each system.

Ok, we see how they work but which is best? Well I'm not going to tell, so there! Actually both types make fine lighting for a reef tank and there is a lot of misinformation about the differences between the two. This centers on that the fluorescent lights are a continuum source while MH is a point source.

A big myth is that MH lights are much hotter than fluorescents. That is really not so. A bank of 500 watts in fluorescents puts out around the same heat as 500 watts of metal halides. The fluorescent tubes spread that heat over the entire length of the tube. A MH light concentrates the heat in a small area. This aids in the belief that they create more heat. The light output is also overstated for a MH. Many say that they produce much more light than a fluorescent (s) of the same wattage. This is just the same as the heat. The fluorescent spreads the light out while the MH emits it in a small area. Sure it looks much brighter but if you add up the total illumination for the fluorescent there is not that much difference.

Well that's about all I can figure your feeble Newbie brains can absorb in one sitting. I'll continue to illuminate this topic in my next post. I'll hit upon which lights work best where and some of the variations in the two lighting types. Light them if you got them!


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Last edited by WaterKeeper; 11/22/2005 at 11:43 AM.
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Old 03/15/2005, 05:09 PM   #2
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Re: Alright Newbie; Let's shed some light on this subject.

Quote:
Originally posted by WaterKeeper


Well that's about all I can figure your feeble Newbie brains can absorb in one sitting.
I'm trying to be offended.

Thanks waterkeeper - when can we expect the next chapter of newbie bashing lighting lecture?



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Old 03/15/2005, 06:21 PM   #3
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can't wait for the next chapter
great job


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Old 03/15/2005, 06:23 PM   #4
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Love these threads
Very helpful



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Old 03/15/2005, 06:25 PM   #5
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Good stuff, keep it up. Thanks.


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Old 03/15/2005, 06:26 PM   #6
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your posting was to long and I got distracted. Could you please repeat your posting


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Old 03/15/2005, 06:41 PM   #7
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Question:

I just finished cyclying my tank and everything checks out fine
tmp 80
nitrate 0
amonia 0
nitrite 0

took a month too.

Is it safe to add the salt now?


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Old 03/15/2005, 06:42 PM   #8
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Whose Thomas Edison?


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Old 03/15/2005, 06:57 PM   #9
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Quote:
Originally posted by Freeskier98
Question:

I just finished cyclying my tank and everything checks out fine
tmp 80
nitrate 0
amonia 0
nitrite 0

took a month too.

Is it safe to add the salt now?
hahaha!!


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Old 03/16/2005, 09:26 AM   #10
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Quote:
Originally posted by Freeskier98
Question:

I just finished cyclying my tank and everything checks out fine
took a month too.

Is it safe to add the salt now?
Dear Newbie,

AHHHH!!!!


Evidently an avid reader of The New Tank Thread.

Sierra,

I'll continue when I figure out what type of tank Freeskier has that is a 250 w 14K HQI.


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Old 03/16/2005, 12:30 PM   #11
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Its an old MH reflector turned upside down....
adds in the light penetration to my corals
BTW i added the salt and my school of 15 nemos yesterday. But about half of them are napping on the sand... they sleepy


keep it up waterkeeper, youve helped a lot over the past few months =)


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Old 03/17/2005, 01:46 PM   #12
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Tom, good intro on lighting.

Can you also explain the difference between the IceCap ballasts and other ordinary stuff? Why do they overdrive it, is it good for the light bulbs, and does it use more electricity?

Thanks!


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Old 03/17/2005, 02:53 PM   #13
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I suggest to have this thread as a sticky thread. Thanks, Tom.


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Old 03/17/2005, 03:38 PM   #14
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Damn it Tom, now I have to paste this into the Library so I can pass it around!!!! LOL Great job as always, keep it up!!


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Old 03/17/2005, 04:06 PM   #15
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I see some of you newbies were missing at head count this morning. Too tough for you huh?

I imagine some of you were involved in that HQI stuff. You can't fool the old WaterKeeper. No wonder Freeskier couldn't tell much about his tank. If you are High on quartz and iodine your lucky to know what day it is much less the details on your tank.

I really hope you have been able to follow me so far in this thread. I think lighting is one of the most difficult topics to understand in reefing. Complicating matters most is that the technology here is in constant change with new equipment appearing almost on a monthly basis.

Anyhow, to this point we talked a little about how these lighting systems work. Whether it is fluorescent or metal halide you have a tube filled with an inert gas. A starter circuit creates an electrical arc in the tube between the filaments. A ballast then limits current going to the tube so the lamp doesn't burn out. In a fluorescent this discharge in the tube excites phosphors coated on the glass tube. These emit light along the entire length of the tube. In an MH system a gas cloud inside the tube becomes very hot and emits visible light. The basic difference between the two types of lighting is that fluorescent lighting is a continuum source, spreading the light out over a relatively large area, while MH is a point source with the light mainly emanating from a relatively small area.

I already mentioned that ballasts for MH lighting ignite the bulb using either a starting probe, probe start, or pulse high voltage between two electrodes, pulse start. Fluorescent lights have a couple of different starting systems too. Almost everyone is familiar with the two common type tubes in use, instant start and rapid start. They are pretty much a household staple. In instant start tubes you flip the switch and the light comes on right away. Rapid start usually has a flicker for a second or two. That is because here the ballast looks at the tube and checks to see that it fired. If not it sends another high voltage jolt to the tube. It does so till in detects that it is illuminated. The oldest method is called pre-heat and is common mainly in power compacts. One of the things about rapid and instant start lamps are they do best in nice cozy environments. Put them out in the cold and they may refuse to function. Instant start lamps in a cold area like Ohio pretty much fail to light if outdoors on a cold March day. Rapid starts have some advantage as their repeated attempts to fire create heat and may get them going in close to freezing temps. They usually fail if below zero temperatures are encountered. One of the oldest methods to fire a fluorescent is a preheat start. Here moderate voltage is applied to first warm the filament. This helps warm and vaporize mercury in the tube. After a short preheat the voltage is kicked up igniting the lamp. This type of lamp will work in cold weather. It also can help a lamp burn longer.

Why? Well every time a lamp is fired the high voltage at the filaments sputters?off some of the filament material. That is some of the filament itself is vaporized. You can visually see this effect in a fluorescent. This is the dark area that forms near the ends of the tube. It is material that leaves the filament and is deposited on the relatively cool walls near the ends of the tube. It fortunately doesn't move much further down the tube. The more often a lamp is started the more material leaves the filament and eventually the lamp fails. In a power compact the filament is fairly small compared to its larger cousins so the filament wouldn't last too long. Using a preheat starting system allows less of a kick?to be needed to fire the lamp, thus reducing sputtering and conserving filament life.

The big thing here is if you use magnetic ballasts make sure they match the lamp's firing method. A preheat won't work on a ballast for an Instant-On type fluorescent. These little subtleties are not usually a worry when doing home lighting as people usually buy a complete light system. In reefing many hobbyists like to experiment and purchase individual components. It is a pain to find that the ballasts and lights you buy don't match. Most electronic ballasts are designed to fire any type bulb so they are an advantage if you plan on experimenting with different lighting types.

One more word about that sputtering?effect I mentioned. In a fluorescent the deposited material is confined to the base of the tubes. Sputtering also occurs in MH. Here it is more of a problem. The material that sputters off coats the entire tube surface, not just the ends. Over time it tends to obscure the tube envelope reducing output and causing a shift in the emitted spectrum. Lamps that allow hotter operation of the tube, such as Ski's HQI, decrease this effect as the tube wall allows less condensation of sputtered material.

I want to mention a little more about the HQI lamps. HQI stands for High Quartz Iodide and has become more or less a generic term for double-ended MH lamps. MH lamps come in two varieties, the mogul based, single ended and the double ended. The first type has nothing to do with those snow bumps on a ski slope. They refer to lamps that screw into a socket much like the bulbs in a table lamp. These bulbs have an inner tube, which provides the light, and an outer glass tube that acts as a safety shield. Most people think that this shield guards against breakage of the light tube inside. This it does but it also provides protection against an unseen hazard, short wavelength Ultraviolet. Shortwave UV is what causes you to get a sunburn when outside. You may have noticed if you sit by a window in full sun you don't get a burn, or tan for that matter. That's because standard glass is a strong barrier to shortwave UV and blocks almost all of it. A fluorescent emits UV but the glass tube does not transmit it. The fluorescent tubes in a tanning booth are made of quartz glass to allow UV to pass. In a single ended MH the glass shield contains the UV but in the double ended there is no shield. To make matters worse, the tube is a high quartz glass. This protects it from heat but does not protect you as quartz passes UV. Double ended (DE) MH needs a glass protective shield on the hood or other fixture! Without this shield serious eye damage can occur!!This shield must be glass or specially coated plastic. Plain acrylic plastic won't stop UV radiation. Please be very careful to see to it this shield is used. Staring up at an unshielded DE tube can damage your eyesight and lead to blindness.

One thing I also haven't mention yet is the T numbers assigned to fluorescents. If you look at a common fluorescent you see a number like F40T12/845. The number following the F?is usually the wattage but sometimes the length. The number that follows the T?is the diameter of the bulb in eighths of an inch. The numbers run up to T17 but only two or three are generally used on aquariums. The first, a T12 is 12/8ths or 1.5 inches in diameter. Most bulbs were T12's in the past but some people did use 1", T8. Lately 5/8?T5's have gotten much attention. We will discuss these smaller tubes shortly.

The last number, here 845, gives two values. The first, 8, is the Color Rendition Index (CRI). This is a value that a standard Observer?sees when comparing colors under the artificial light to true sunlight. A value of 100 means the bulb matches sunlight completely. Here in the number 845 the 8 means that the bulb shows colors at about 80-89% of that as observed in full sunlight. It use to be that the Standard Observer?was Clark W. Griswold of Chicago, Illinois but since it was leaked he was colorblind there has been a replacement. I have no idea who that is.

The last two digits in the 845 are the color temperature, K, times one hundred, so in this case the bulb has a K value of 4500. Sometimes there will be letters following those numbers. A HO for instance is high output. Unfortunately, the manufactures often take liberty with the system and don't label their tubes in this fashion.

Well, we are now starting to get into things like CRI so I think it is time to assign some homework. There are many terms used in lighting so look up Color Rendition Index (CRI), Kelvin, lumens, lux, candlepower, foot-candles, lamberts, phot, apostilb, Photosynthetically Available Radiation (PAR), Photosynthetically Available Usable (PUR), Photosynthetic Photon Flux Density (PPFD), Einsteins, and E=(π/4)δ2Ω(I think the last is the name of a Fraternity).

Well I ready for some corned beef and cabbage. Great chow on a fine day for the Irish. Till next time.


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Last edited by WaterKeeper; 11/22/2005 at 11:47 AM.
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Old 03/18/2005, 11:40 AM   #16
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Didn't get much sleep again last night; did you Newbie? Too busy calculating the number of Lamberts in a differential solid angle's total steradians I bet.

I closed yesterday with a list of lighting terms. Most of those I hope you never need to use but some of those are pretty common and probably need explanation.

Go to the good old Home Depot's lighting department and you see that most lights have the total lumen output shown on the box. Gosh darn? you say, That Sylvania Cool White Deluxe certainly packs in the lumens.?

Lumens are not all that hard to understand. Just take a look at that muscle car sitting out in the driveway. It has a 3.5 liter 351 horsepower engine. Lumens are much like horsepower. They give a general idea of how much power a light source packs. In fact, lumens can be directly compared to an electrical standard, the watt. One watt equals 683 lumens give or take a few. So a 100 watt incandescent gives out as many lumens as a 100 watt fluorescent of a 100 watt metal halide, Right?

In theory they would all be equal giving out 68300 lumens each. However, let's look again at that muscle car. Sure it has 351 horsepower but how does it compare to other cars that also have 351 Hp engines? We all know that things like torque, gear ratio, vehicle weight, and tire type will affect how much of that engine horsepower will translate to speed in the quarter mile. That's much like lumens. They tell you how much light is theoretically available but don't say a thing about how much of that light is usable or will provide the desired result in your tank. None of the lights listed will actually produce 68300 lumens. It is always much less. Some of it is lost in heat or absorbed by the glass envelope of the light itself. There are many variables involved.

OK, it is time for a practical exercise here. We could do this with some heavy duty math but a little visual demonstration is far simpler.

Take that trusty old Maglite and adjust it to provide an even beam. Hold it about a foot away from the wall and note the size. Now move that light to two feet away and now look at the size of the beam. It sure has grown hasn't it? In fact, it now covers an area four times as large as it was at one foot. Now move it back to 4 feet. The illuminated area is now 16 times as large and, you will notice, much dimmer. It dims because the bulb in the Maglite only gives off a fixed number of lumens. As the light is moved further from the wall the lumens must cover a larger and larger area with the same amount troopers (lumens). Eventually, as the light is moved further away, the troopers are spread so thin they are barely visible. The intensity of light falling on a given area is defined in lux. Lux have the unit of lumens/ meter2. As a light source moves further and further from what it illuminates the lux decrease as the inverse of the square of the distance. In other word doubling the distance doesn't halve the light intensity but decrease it to one-forth as much.

Another interesting thing is happening in our demo that we should note. What are we seeing when we look at the light beam on the wall? We are not seeing the light source itself but rather a reflected image of the actual source. That image is, in most cases, not identical to the light source. For one the image is getting more radiation than our eye. Why? Because the light needs to travel the distance from the wall, where the image is formed, to our eye. This trip from the wall to eye further reduces the lumens we see. One other thing before you turn the Maglite off. Instead of holding it perpendicular to the wall move it so it hits the wall at a angle. The beam appears as an egg shaped ellipse with the most lumens hitting the small end of the egg and decreasing as we move toward the large end. Another thing is happening, depending on the surface, some of the light hitting the wall may be absorbed or it may shift its spectral output from that of the original source. In other words a color shift.

We have two separate factors when we are dealing with light. Actual emission, coming from the source and reflected emission coming from the area where the light strikes.

Actual emission is important in what the critters in our tank's "see" from the lights we buy. Reflected emission has several effects. It allows us to add reflectors into the hood to direct light to the area we wish to illuminate and it effects how our eyes see the objects under illumination. Both of these are important considerations in choosing our lights.

Well it's Friday and I'm sure most of you want to knock off early and suck down a few near beers over at the PX. We'll cover more next time.


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Old 03/18/2005, 03:43 PM   #17
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Great information Waterkeeper, I'll keep tagging along.

Thanks, Droptine


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Old 03/19/2005, 02:36 PM   #18
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Quote:
Originally posted by dchao
Can you also explain the difference between the IceCap ballasts and other ordinary stuff? Why do they overdrive it, is it good for the light bulbs, and does it use more electricity?
Hi Chao

Sorry I didn't see your question the other day. IceCaps are electronic ballasts meaning they can run different types of lights, run cooler and use less electricity than the run of the mill magnetic ballast. There are other bands of electronic ballasts available so you need to weigh the claims and choose a brand you trust.

Over-driving is just taking something like an NO fluorescent, 0.5 amps, and having the ballast supply current like it was an HO, 1.0 amps. You get more output but there is always a cost in decreased tube life. It is a little like overclocking the CPU in your computer. It speeds things up but the heat generated in the process can cause melt-down of the CPU. It is not as dramatic with fluorescent lighting but one should take into consideration the costs vs. the benefits.

Over driving a MH bulb can be more dangerous. The extra heat may weaken the light tube jacket and cause the bulb to burst. Being showered with molten glass is not a lot of fun.


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Old 03/19/2005, 02:50 PM   #19
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Great info as always Tom


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Old 03/19/2005, 08:10 PM   #20
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very helpful post and great info.. thanks for taking the time i look forward to reading more!


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Old 03/21/2005, 01:39 PM   #21
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Anybody find any great deals on lights at the PX on their weekend furlough? The local PX here only has good deals on Bud or Miller Neons.

Well, we have talked about lumens and they are about as useful as whipping out that light saber of your's in intergalactic space. All that energy goes off in every direction. Sure it may be real long and shiny but unless there is someone there to observe it then all that penetrating power is lost.

That is where lux come in. Lux determines how many lumens actually reach the target. In this case the stuff in your tank. We can measure lux with a simple photographer's light meter. A light meter is nothing more than a photocell that gives off a voltage in proportion to the light that strikes it. Since lux is a measure of lumens per square meter the light meter indicates that on the dial.

Now remember early in our discussion I said you can tie watts directly into lumens,1 watt=683 lumens. If that left you scratching your head as to how so many lumens could come form a single watt then we need a dig a little deeper. Old Clark Griswold, our standard observer, said that he could only see things well at precisely 555 nm. In honor of Clark that wave length was chosen for the lumen.

You also may remember good old


ROY G. BIV


From elementary school science. He's the guy that helped you remember the colors of the rainbow which is a thinly disguised way to fool you into learning about the electro-magnetic spectrum. Well 555 nm is just about G in Roy's name.

To get one watt to produce 683 lumens of light means all the energy is converted to light and that light is emitted only at 555 nm (It would also take a small miracle.).

Our eyes are most sensitive to light in the yellow-green region centered on 555 nm. When lumens were introduced as a measurement system it was decided to use this single wavelength as the benchmark. If you use a photographer's light meter the meter is "weighted" to favor this region of light.

This is all well and good in the area of photography but not so hot when it comes to keeping things alive in a reef tank. Photosynthetic life is important in a healthy reef. Be it coralline on the live rock or zooxanthellae harbored in the coral they need light to survive. Unfortunately, light at 555 nm is not it.

Well, the entire visible spectrum plays a role in photosynthesis, it is just 555 nm is not exactly the wavelength that most algae would choose if put to a vote. If I plan to take a picture then using a regular light meter is fine. If I plan on illuminating a reef tank it tends to fall short.

One of the first lights to make headway into the world of reefing was the actinic fluorescent. Actinism is the term for light that induces chemical reactions. It just so happens that light in the region of 420-450 nm is very important to photosynthesis, a chemical reaction. Actinic lights produce much of their light at this wavelength. Actinic lighting may have been somewhat of a novelty turned important. When it first came out around the late 70's it was mainly touted as great tank lighting because in highlighted the fish. The LFS loved it and many of their SW tanks had it. If you can see a tank with just actinic lighting in use you'll see what I mean. Under actinic the water appears more transparent and fish and coral tend to stand out. Some corals even fluoresce under these lamps.

It was only after they were in use for awhile that the other benefits to a reef tank became apparent. An actinic lamp has a terrible CRI (about as bad as you can get ) but in a reef tank it adds an abundance of useable photosynthetic radiation. That, and with its ability to highlight the critters inside the tank, made it all the rage. Suddenly corals that have never been able to survive in a tank where not only surviving but growing. Actinic lighting is one of the great advancements in reef husbandry.

As with all big advances improvements are constantly being made and actinic lighting is often put on the backburner these days. For my part I still believe part of any tank's lighting should be actinic. I still feel it is beneficial in a tank with any other type lighting.

Well if you take your light meter and check out the lux supplied by those actinic lights you will not be very impressed. Next I'll talk about some new improved methods of light measurement which will knock you on your Quanta.


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Last edited by WaterKeeper; 03/22/2005 at 11:37 AM.
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Old 03/21/2005, 03:58 PM   #22
SpaceFish
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Awesome read.. thanks so much for taking the time. Your stylings always keep me glued!

~R


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Old 03/22/2005, 07:44 PM   #23
Dr4g0nf1y
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I wonder if anyone has honesly ever done a review of Lighting like they've done of different Salt mixes?


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Old 03/23/2005, 05:51 AM   #24
silkchaos
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Waterkeeper, I got the lights and bulbs, put them in the tank, plugged them in and now everything is dead! What did I do wrong??

(Thanks for continuing to post great information!)


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Old 03/23/2005, 09:40 AM   #25
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Quote:
Originally posted by Dr4g0nf1y
I wonder if anyone has honesly ever done a review of Lighting like they've done of different Salt mixes?
http://www.reeflightinginfo.arvixe.com/
http://www.cnidarianreef.com/lamps.cfm
http://www.advancedaquarist.com/issu...03/feature.htm

These are a few that I've seen

~R


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