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Discussion Starter · #1 ·
sorry if this is in the wrong section, but i figured parts and construction would work just fine. Maybe beginners section would be a better fit.

What i thought we could do is compile some common lighting terminology and talk about the science behind it i suppose. I see a lot of confusion on the lingo and such, so i think this might be nice for newcomers. Hopefully this works out!

Different types of bulbs

Most lights we see in use are fluorescent so I'll go over these first. So what exactly is a fluorescent light bulb? As many know, the main element of a fluorescent bulb is the sealed glass tube. Inside there is mercury, and an inert gas (usually argon). The electrodes on both ends of the tubes send AC current through it, vaporizing some of the mercury. This AC current is sustained by a ballast. As charged ions and electrons move through the gas inside the tube, they collide with the vaporized mercury atoms which excite the mercury atoms, eventually creating light.

However, most of the light created by this process is ultraviolet, and not visible. This is where the white coating on the inside of the fluorescent bulb comes into place. It's actually powdered phosphors. When a light photon hits a phosphor atom, it converts it to the white light we can actually see.

Ok, so we sorta know how they work now, but there are tons of different types of fluorescent lights out there. I'll go over the most common ones in this section.

First, there are the linear or tube lights. These are classified by their wattage, and diameter. You normally see things like F24T5 on a bulb or package. The F24 means that it uses 24 watts of energy; pretty simple. The T5 part however, seems to get people confused quite a bit. Its really just talking about diameter, but in eighth inch increments. A T5 bulb has a diameter of 5/8", a T8 = 8/8" or 1", a T12 = 12/8" or 1-1/2", and so on. Fairly simple. Note that most shop lights use either a T8 or T12 bulb, while a lot of commercially made aquarium lights use T8, T5, or T5 high output.

T12, T8, T5 size comparison


The next type of fluorescent bulbs i'll talk about are CFL's, which stands for compact fluorescent. Just like the linear bulbs, these come in all different sizes and shapes. Like the name states, cfl's are compact, therefore you can put them in smaller spaces than a T8 or something of similar output and wattage would not be able to fit in. I'd say the most common of these are spiral cfl's which are the swirly little bulbs with the screw in base commonly available at most convenient stores. They can range anywhere from 5 - 100 watts usually, and have their own self contained ballast.

Spiral cfl


The other type of cfl's are somewhat similar to linear bulbs, but consist of 2-4 small tubes connected to each other, allowing electricity to flow through all of them simultaneously. Sometimes these are referred to as power compact bulbs. PC's DO require a ballast. They are not self contained like spiral cfl's. Normal sizes generally range from 13 - 96 watts, but can go higher than that.

a double and quad power compact


There are a lot of odd ball cfl's out there, but they're not used to much in the hobby, so i don't really feel the need to touch up on them.

Next type of lighting is HID lights which stands for high intensity discharge. These use an arc of plasma that shoots between two tungsten electrodes producing light. These electrodes commonly housed inside a fused quartz arc tube containing inert gas and different types of metal salts. Once the Arc is struck, the salts and mercury vaporize and help with light output and power consumption. HID lamps have very high light output which is practical for large or deep tanks. Although they have lots of light output, they typically consume a lot of power (normally around 150-400 watts) and run fairly hot which can heat up a tank in no time. Most common forms of hid lights are metal halide (MH) and high pressure sodium (HPS)

a commercially made power compact and metal halide fixture


This graph shows the large light output of a metal halide unit.


Alright, this is probably where the majority of confusion takes place in my opinion. Color Temperature

Color temperature (also known as the Kelvin temperature or kelvin rating) is essentially the color of light that the bulb gives off. Let me make this clear. Kelvin temperature does not have anything to do with how much light is put out. It just gives us an idea what the average color of the light appears to be. Most bulbs we normally find are in the 2700k - 10000k range. A kelvin temperature of 2700k will appear to be slightly yellow, while a kelvin temperature of 10000k will appear more blue.

This is a pretty accurate representation of the kelvin scale in relation to light.


When we look at a graph of a light bulb, it shows is how much light it puts out in certain parts of the spectrum. Instead of kelvin, it shows this to us in nanometers. That's just the wavelength of the light. Most lights we use over our tanks put out light all over the spectrum, usually between 400 and 700 nanometers or nm for short. Here is a picture explaining it a little better.


Light intensity

Again note that kelvin temperature does not effect light output. There are a few ways we use to determine light intensity. Probably the most used is lumen output. Its pretty hard to understand the real definition. I don't even really understand it hahaha, but anyways, its basically how much light the human eye perceives. This isn't a foolproof method though. Lumens only apply to the part of the spectrum the human eye can see, which isn't necessarily the whole spectrum plants ultilize. The human eye sees light the brightest at around 550 nanometers (which is the blueish green part of the spectrum). Plants do not utilize green light. It merely bounces off of them, which is why they appear green to us. You can see how lumens might not be 100% reliable for our use.

As a scale, a normal 15 watt spiral cfl puts out about 800 lumens, while a 24" F24T5ho bulb puts out around 2000 lumens. This kind of gives you an idea how much light each one puts out in relation to one another. Not all light bulbs are the same though. You may have two of the same size and wattage bulb, and they may have different light output. Also, over time, light output decreases. For example, take that 24 watt t5ho i mentioned earlier. At the beginning of its life, it puts out 2000 lumens. We call this its initial lumens. After 40% of its rated life, it only puts out 1880 lumens. This is called the mean of lumens. Be sure to replace any bulb after a year for this reason.

CRI- you may have heard of this before. it stands for color rendering index, which basically means how accurate the light is at showing the true color of things. It is on a scale of 100. The sun and most incandescent lights are at the top at 100, but most fluorescent bulbs tend to be around 80 or so. Some better brands of bulbs might have a higher CRI of 90-95. 95 is really good actually. Personally, i wouldn't buy a bulb that has a CRI below 70 or so. It start to make things look really washed out.

Photosynthesis- I'm not going to touch to much on this issue, as I'm no chemist or anything. Far from it actually... Basically all you need to know about it is that the chlorophyll in plants utilize just about all of the visible spectrum except the green part. Photosynthesis peaks right around the red and blue areas (around 450 nm and 650 nm) also.

Graph showing what i explained above


Reflectors and restrike- When a light bulb emits light, it goes in all directions. As you can imagine, some of is gets wasted because it doesn't go directly down into the tank. That's where reflectors come into play. They take the light going up and redirect it back down into the tank. Sometimes the light going up is bounced directly back down onto the bulb itself. This causes excess heat and shortens the life of the bulb. A cool bulbs runs better and longer. Restrike is a big problem with spiral cfl's mainly because the twisted tube that emits light is very close to itself, so naturally a good amount of light gets wasted by hitting the bulb part.


Picking out a light and bulb that suits your needs- This is really based on personal preference. Every type of light has its place in this hobby, but in my opinion unless you have a large or deep tank, fluorescent is probably your best bet. CFL's are good for restricted space, while linear tubes are better if you have the space. If you are buying your fixture, make sure it has a solid construction, good reviews, operates without much excess heat, has quality reflectors. I personally like to build my own light fixtures. That way if i need to modify something, or if anything breaks, it isn't hard to fix.

As for bulbs, its all about what you like. You always want to get a "daylight" or "full spectrum" bulb. Any kelvin rating from around 5500k to 10000k will work fine for growing plants. If you get a more yellowish bulb (around 5500k) the reds of your plants will stand out more, but if you have a more blueish bulb, the greens will stand out more. Typically, a lot of people go right in the middle with a 6500k. These work great. You can also mix and match different ones to suit your tastes. There are also a good amount of daylight bulbs with plenty of output in both the blue and red part of the spectrum. A lot of commercially made planted aquarium lights will come with 2 bulbs, usually one more reddish, and one more blue. For example, the Current USA nova extreme fixture comes with one bulb that peaks around 480nm and another around 650nm.

Well i sure hope this clears up some confusion among beginners that don't know where to go or what to get in terms of lighting. Feel free to add anything that i missed, and don't hesitate to correct me if i'm wrong on something!

Ryan
 

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Discussion Starter · #4 ·
hahaha wow! glad you guys like it. U really think it's sticky material?? i just didn't want to do my homework so i ended up making this lol :p
 

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Yeah, that was a really good post. Thanks for not doing your homework (me, I was doing my homework however while you were writing this apparently)

Why are straight florescents preferred over CFLs?
 

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Discussion Starter · #7 ·
yes a t5 high output has more lumens, and uses more power at the same time. More often than not, t5ho is more efficient (by that i mean more lumens per watt of power consumed) than a normal t5. They might run a little hotter though.
 

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Discussion Starter · #8 ·
Yeah, that was a really good post. Thanks for not doing your homework (me, I was doing my homework however while you were writing this apparently)

Why are straight florescents preferred over CFLs?
they are generally more efficient, and spread the light out more evenly than a cfl. Seeing that they are straight, there isn't as much restrike as a cfl, which means that linear fluorescents will run a little cooler. At least that is what i have found in my experience. Hope that helps! :D
 

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Really Outstanding.
Is there a difference in the amount of reflected light between stainless and white shop lights? Would there be any benefit to adding aluminum foil to white shop light reflectors?
 

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Discussion Starter · #11 ·
actually white paint is a really great reflector, and aluminum foil can be IF YOU DO IF RIGHT the thing is, if you put down aluminum foil behind a shop light, and it gets all crumpled, the light just bounces off these bends and creases as it would the facets on a regular reflector, but in every direction instead of down into the tank. Therefore the light just gets diffused and is a lot less effective than plain old white paint. I have actually used aluminum foil by gluing it down and flattening it out with a roller to make it perfectly flat. That seemed to work very well, but in my opinion, white paint is better just because its way less of a hassle hahaha. When i build my lights, i either use commercially made polished aluminum reflectors, or i just paint the inside flat white. Oh and some people have used Mylar with good results as well.

Thanks for all the compliments you guys!

Ryan
 

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Nice post, I learned quite a bit in a few minutes about lighting than I thought possible when I saw the title. Thanks for sharing.
 

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Really Outstanding.
Is there a difference in the amount of reflected light between stainless and white shop lights? Would there be any benefit to adding aluminum foil to white shop light reflectors?
Flat white (not gloss ironically), reflects more light then most anything else except specialty materials, even more then most mirrors. Brushed aluminium and silver, even tin can also reflect quite a bit of light and there are some variations of mylar that do really well, and probably rival or surpass flat white. Aluminum foil in theory wouldn't be to bad but the wrinkles cause the light reflected to be scattered, often in directions that aren't useful to your purpose. Its counter intuitive but the "dull" side of aluminum foil actually reflects more light then the shiny side does, so if you use it you want light hitting the dull side. At one time I was able to find some tables of what materials reflected light best but in a quick search I didn't have much luck this time. Generally though brushed metal surfaces, and flat white are going to be your best bets. Usually the smoother a surface is the better also as it directs light where you want it more instead of scattering it.

So just spray painting the inside of any fixtures flat white will give you some of the best results for the least expense. (cover the electrical sockets/components, and remove the bulbs of course)
 

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Should be sticky. Many thanks for your work ;)
 

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Discussion Starter · #16 ·
Would a reflecter that has a more curved shape be noticeably better than one that has "corners" and flat surfaces like in the exo-terra lights?
I think it really depends on what kind of bulb you are using. If you just have a linear bulb, i think more a curved "parabolic" reflector would bend more light around the the bulb and back into the tank. TEK reflectors are pretty popular for t5 bulbs and they have twenty something facets that basically make it a bent surface instead of having sharp corners.

For cfl's on the other hand, they arent perfectly round in diameter, so reflecting the light is a little more difficult. A larger reflector with more corners and flat facets are usually used. The AH supply MIRO 4 cfl reflector only has 5 facets, but works really good. I have their 2x36 watt cfl kit over my 30 gallon planted tank.
 

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Discussion Starter · #17 ·
would a mod care to make this a sticky please?? i think a lot more people would end up seeing this, helping more people in the long run
 
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