T5s vs. MH... What would be the ultimate faceoff?

[pitbullpooch]

Originally posted by kmacartney
OK, now I need to read this thread with a dictionary and electrical engineering text.

your not the only one lol

[The Grim Reefer]

By the time you are say a foot away from a 4 foot fluorescent tube you will be getting a lot closer to the light degridation following the ISL than not. What affects them more than being linear is the fact you are using multiple lamps. The light from ajoining lamps is a lot closer to the target (coral or PAR sensor) than the light out at the ends of the lamp. The Linear aspect of the lamp, the array effect (mutiple lamps) the parabolic reflector and the ability to place the lamp so close to the water all play together to make the T5's so efficient.

[danskim]

Haha people around here sure like to bicker.

[abigdog1976]

Any updates? Really interested in the outcome since we too moved from 3 400w w/vho to the aquatinics 72 inch 14 bulb fixture about 7 months ago

[jamesdawson]

Hello Sanjay,

How is this project going?

Thanks,

James

[tcmike64]

Hey Sunjay, just wondering, have anything good in store for IMAC? Look forward to meeting you there

[Rovert]

Sanjay, I don't know if this was already addressed, because I didn't have the patience to read through 12 pages and 300+ posts to find out, but there is one thing I think should be considered.

Early in the thread, gcarroll suggested that T5s be given a 4" handicap. Respectfully submitted, I think this is a mistake. I'm not an engineer or scientist, but it was always my understanding that in a scientific test, the objective is to remove as many variables as possible. By "handicapping" the lights, by definition, that unfairly places a bias into the matrix from the outset.

To make my point by going to an extreme, why not give the T5's a 4 foot advantage, or just move the Metal Halides into the next room, for that matter?

IMO, the tests should be done with fair and consistent positioning of lamps, otherwise the results will be skewed. I think the measurements should be taken at the same distance from the lowest parallel surface of the reflector, because that's the factor users will make in determining distance above the tank or waterline. If the lamps are mounted in a reflector which happens to already be 6" high (as in the case of MH reflectors), and the T5 reflectors only 2" high, then so be it.

Sorry if I seem 'cheeky', or if this has already been addressed, but it just doesn't make sense to me for an experiment to be done to make a comparison by starting from the outset to disadvantage one lamp/reflector/ballast array over the other.

[thriceanangel]

I think that placing the lamps where they are or will be placed is fair. This is a T5 vs MH faceoff. The advantages and disadvantages should be fair play. You cannot hope to get a MH bulb as close to the water as a T5 for many reasons. That is one of the advantages of using T5. By your argument, maybe he should black out the entire length of the bulb except for the 1" to make both bulb lengths equal? The test should be to accurately judge both bulbs in a real life, working situation.

JMHO of course

[pitbullpooch]

Originally posted by thriceanangel
The test should be to accurately judge both bulbs in a real life, working situation.

thats exactly what i was thinking. From what i understood this test is a face off of them in a situation in which there gonna be used on our tanks so having them the same height wouldnt be the way that we use them on our tanks and to me would be a pointless test for us wanting to know how they measure up against each other when used on our tanks. this is just how i take it and what i thought this faceoff was all about.

[Rovert]

Originally posted by thriceanangel
I think that placing the lamps where they are or will be placed is fair. This is a T5 vs MH faceoff. The advantages and disadvantages should be fair play. You cannot hope to get a MH bulb as close to the water as a T5 for many reasons. That is one of the advantages of using T5. By your argument, maybe he should black out the entire length of the bulb except for the 1" to make both bulb lengths equal? The test should be to accurately judge both bulbs in a real life, working situation.

JMHO of course

I see your point, and kinda agree, but kinda not. We might be thinking the same thing, but saying it different ways.

The example of blacking out a portion of a T5 is not germane, because it's another disadvantage by way of skewing conditions, reducing the bulb to less than 100% of its available output. Likewise, putting T5's into watertight glass tubes and submerging them closer to a sensor would also render false and useless results, which is effectively what giving them a four-inch "handicap" does by unfairly skewing the conditions to potentially favor them in the results.

Though I understand the merit of wanting to compare both lamps at their respective advantages, perhaps there's a happy medium whereby we accomplish both things.

Both these types of lamps have more-or-less standard reflector assemblies. These respective reflector assemblies have been designed to maximize the output of the lamps.

As you indicated above, if we install and test said assemblies in a manner consistent with their use (say, for argument's sake 1" above the waterline) that would be a test constant that would be fair, because it's the REFLECTOR that is determining bulb distance from the bottom of the tank.

For example, a standard MH reflector places the laps about 4" to 6" above the bottom edge of the reflector assembly. For argument's sake, if the garden variety T5 parabolic reflector mounts the bulb 1" above the bottom edge of that type of reflector, then we sould be measuring from the bottom edge of each type of reflector. Although the actual vertical placement of the bulbs as mounted is different internally, it's the ASSEMBLY that we're testing, since the whole of any lamp/reflector combination is greater than the sum of its parts.

In other words, don't equalize or adjust distances for the lamps themselves, pick a test constant of 1" above the waterline for the reflector, given the reflector is designed for the respective type of lamp.

Hope I made sense, here.

[The Grim Reefer]

All we really need to know is how much the T5's gain moving closer to the target. If we have a measurment at say 16", 12" and 9" we will have an idea of the advantage gained by being closer to the water.

[Rovert]

Originally posted by The Grim Reefer
All we really need to know is how much the T5's gain moving closer to the target. If we have a measurment at say 16", 12" and 9" we will have an idea of the advantage gained by being closer to the water.

Uh... but isn't that true of any lamp? Doesn't any lamp gain in intensity when it moves closer to the target?

I still believe that for the most accurate comparison, we ought to be evaluating the lamp/reflector ASSEMBLY, not just a raw bulb. I believe that would be a serious mistake.

I think a picture would really help clarify what I'm trying to explain. See the diagram below. IMO, the most consistent way to test these lamps is to use the bottom edge of the reflector, no matter what distance it is from the sensor, as it is a uniform and consistent reference point.

Given that each type of reflector is designed for its respective lamp, though the two reflectors are different shapes, sizes and the lamp mounts at different heights within the reflector, it's BOTH the reflector AND the lamp as an assembly that we're testing... not just the lamp itself.

Anything else would lead to misleading results, in my view.

[thriceanangel]

No because of the heat and proximity to the water you would never have a MH bulb that low. It's unrealistic. Also it would also be a disadvantage to the MH when using a 36" tank w/ a 250W bulb and a lumenarc reflector. The reflector would not push the light out to the sides of the tank effectively. It has to be higher. I don't think anybody would use a MH light in this fashion. It would be dangerous to do so I think.

Also I don't think that there is anything more or less standard in T5 lighting reflectors. I don't know about MH, I haven't read any of the comparisons because I haven't needed to. But as far as T5 is concerned, which reflector used means ALOT to the total light output of the fixture.

Grim- Isn't light dissipation over a distance a calculated quantity using the inverse square law? The only variability would be in that there are hot spots in the light. So moving the light to different distances would only magnify or diminish those hot spots.

[hahnmeister]

Actually, I can use my Lumenarc DE above my 40B at only 4" from the water surface... the same that my T5 is. I get light at the edges of the tank too.

[Rovert]

Originally posted by thriceanangel
No because of the heat and proximity to the water you would never have a MH bulb that low. It's unrealistic. Also it would also be a disadvantage to the MH when using a 36" tank w/ a 250W bulb and a lumenarc reflector. The reflector would not push the light out to the sides of the tank effectively. It has to be higher. I don't think anybody would use a MH light in this fashion. It would be dangerous to do so I think.

Also I don't think that there is anything more or less standard in T5 lighting reflectors. I don't know about MH, I haven't read any of the comparisons because I haven't needed to. But as far as T5 is concerned, which reflector used means ALOT to the total light output of the fixture.

Grim- Isn't light dissipation over a distance a calculated quantity using the inverse square law? The only variability would be in that there are hot spots in the light. So moving the light to different distances would only magnify or diminish those hot spots.

I think you haven't read my posts clearly.

Pick whichever reflector you want for each type of lamp. Just be consistent with the test! The measurements should be 'x' inches away from some reference point for both types of lamps/assemblies. I believe that reference point shouldn't be the bulb, but the bottom edge of the reflector - whichever reflector it is that is chosen.

Then, when we establish one set of baseline numbers, we can change reflectors to test for that variable and yield a conclusion about the efficacy of different reflector designs, should Sanjay have the energy and patience to deal with that.

I just don't understand why the concept of consistency and removing variables should be so problematic when we're trying to establish SCIENTIFIC results. Unless, of course, you're invested in the outcome for personal reasons.

If you just willy-nilly make up rules on-the-fly to favor one type of lamp against the other, this study will yeild the best results that a preordained conclusion and the intentionally introduced errors can make of it.

On a side note, I keep my MH reflector 2" above the waterline. That puts my lamps about 6" above the waterline, a perfectly reasonable distance to illuminate a 72 bowfront, and not "dangerous" in any way that I've seen over 6 years of this installation. Seems your comment above was made without any firsthand experience with MH lamps.

[thriceanangel]

I use both systems, so I have no bias really. So you are saying- so I am clear, to use the edge of the reflector as a reference point, not to place the edge of the reflector at the edge of the tank? If this is what you are saying I was definitely misinterpreting you.

I have my T5's with the edge of the reflector about 1/4" above the tank edge. Which is about 1 1/4" above the water, and the bulb is maybe another 1" above that. I would never place my MH this close to the water. I do get plenty of salt that I have to wash off the covering weekly, but my MH reflectors are 4" from the edge of the tank and the DE bulb is another 3" above that, plus 1" to the water- That is 8" from bulb to water for MH compared to the T5's 2 1/4". And the reflectors aren't even close to the same distance from the tank edge.

So I do hear what you're saying about doing it willy nilly, but the advantages are that I CAN put my T5's that close to the water, and I CAN'T put my MH that close to the water. It's kind of an apples and oranges type of thing, either way the conclusion will be skewed. I personally wouldn't consider it valid because the test wasn't done in working conditions. It's the difference between lab testing and field testing. I personally wouldn't fly in a plane that hadn't been tested in the real world, with non test pilots in real working conditions and weather. What the plane design does in a wind tunnel, and what it does in real life situations can vary alot. The best testing is the field testing, providing life isn't at stake. And putting the lights where most people use them only makes sense. Not making every attempt to make them equal.

I thought you were saying (and I did read quickly) to have both lights at the edge of the tank, and that would be way off. But I totally agree with you that it should, and has to be an evaluation of a bulb/reflector assembly. For T5's- it's all about the reflector. But it shouldn't be a measurement of which reflectors are better than others in the same category- I get the feeling that Sanjay doesn't have the time or patience to get into all of that.

But maybe like 2 or 3 different reflectors for each type of light might be good.

[Rovert]

Originally posted by thriceanangel
... So you are saying- so I am clear, to use the edge of the reflector as a reference point, not to place the edge of the reflector at the edge of the tank? If this is what you are saying I was definitely misinterpreting you.

I have my T5's with the edge of the reflector about 1/4" above the tank edge. Which is about 1 1/4" above the water, and the bulb is maybe another 1" above that. I would never place my MH this close to the water... my MH reflectors are 4" from the edge of the tank and the DE bulb is another 3" above that, plus 1" to the water- That is 8" from bulb to water for MH compared to the T5's 2 1/4". And the reflectors aren't even close to the same distance from the tank edge.

...the advantages are that I CAN put my T5's that close to the water, and I CAN'T put my MH that close to the water. It's kind of an apples and oranges type of thing, either way the conclusion will be skewed. I personally wouldn't consider it valid because the test wasn't done in working conditions. It's the difference between lab testing and field testing.

*sigh*

We're getting closer.

Yes, I believe the test should be done using as a reference point the bottom edge of any given reflector, because that's the factor that we use when we judge the distance from the waterline (or above the tank frame) to mount them. That makes this, in fact, a very real world test.

Yes, you could place the leading edge of the reflector at the very edge of the top of the tank for testing purposes, since there will always be a variable in water height anyway. Given the sensors Sanjay will be using are going to be ~20" (or other sampling heights) from the Z reference point to simulate a 20" deep tank, how far down from that point you keep your waterline or how high above the frame you mount the lamps really doesn't matter in the grand scheme of things, so long as the reference distance is stated, and consistent.

No, you CAN'T put MH closer to the water, because then you wouldn't be mounting them IN the reflector. Just look at the diagram again, please. That means, yes, that T5's are inherently closer to the waterline, not because of the distance YOU chose to place the bulb from the water, but because the design of the reflector forces the choice on you.

Ergo, if you've understood that we're not testing just a lamp, or just a reflector, but the LAMP AND REFLECTOR, then you should understand that there is no "advantage" or "disadvantage" to EITHER, because the distance is a decision forced on us by the inherent design of the technology.

Ok, so I've done as much as I can to get this across. I'm throwing in the towel. If you're still not clear on what I'm trying to explain, perhaps someone else can take a crack at it.

[The Grim Reefer]

I guess I didn't do a good job of making what is an obvious point (to me anyway). It doesn't matter or do us any good to use some arbitrary distance as a handicap to account for the fact that T5's can usually be placed closer to the water. Each setup is different. In some cases the T5's might be the same height as the halides.

If you measure halides and T5's at the same but multiple distances it will be easy to figure out the gain by being able to place T5's at closer to the water than halides

Example

PPFD for T5 24" = 1000 20" = 1400 16" = 1900
PPFD for MH 24" = 1200 20" = 1700 16" = 2300

Knowing how much of a increase is gained moving the T5's say 4" closer to the water than the halides makes a real world comparison simple. Granted it wont be exact but should be close enough. Ideally we would have measurments in 4" increments starting at 36" so we would have a more exact . Thats a damned big jig. Got lots of wood Sanjay?

Originally posted by Rovert
Uh... but isn't that true of any lamp? Doesn't any lamp gain in intensity when it moves closer to the target?

I still believe that for the most accurate comparison, we ought to be evaluating the lamp/reflector ASSEMBLY, not just a raw bulb. I believe that would be a serious mistake.

I think a picture would really help clarify what I'm trying to explain. See the diagram below. IMO, the most consistent way to test these lamps is to use the bottom edge of the reflector, no matter what distance it is from the sensor, as it is a uniform and consistent reference point.

Given that each type of reflector is designed for its respective lamp, though the two reflectors are different shapes, sizes and the lamp mounts at different heights within the reflector, it's BOTH the reflector AND the lamp as an assembly that we're testing... not just the lamp itself.

Anything else would lead to misleading results, in my view.

[The Grim Reefer]

As far as where to make the measurment from, lamp or reflector, Sanjay should use whatever standard he has used in the past. If he changes his method all his previous data on reflector performance will be useless if you want to compare output to a T5 system.

[Rovert]

Originally posted by The Grim Reefer
As far as where to make the measurment from, lamp or reflector, Sanjay should use whatever standard he has used in the past. If he changes his method all his previous data on reflector performance will be useless if you want to compare output to a T5 system.

Ah, well if that's the case, then yes, though that's important information to know. My understanding was that this would be a new study from scratch using a known MH ballast/lamp/reflector assembly.

[leebo_28]

ok...so who won??

[pitbullpooch]

I thought this was a face off to show which was better when used in the actual way that we use the lights? to me it wouldnt be a real faceoff if there not put up against each other in the way we use them on our tanks.

[The Grim Reefer]

Who's to say how high off the water each set up would need to be? If you run a chiller it is possible to run halides as low as T5's.

It's better to know how height positioning effects the performance. Then you can detirmine how your particular application will effect the performance.

[thriceanangel]

[QUOTE]Originally posted by The Grim Reefer
[B]Who's to say how high off the water each set up would need to be? If you run a chiller it is possible to run halides as low as T5's.



Whoever does the test should gather some information as to how high above the tank edge each fixture is. Take the average.

I wasn't forced to choose the height I did above the water in either of my fixtures. My T5's are as close as they can get...period. My MH are at the height they are for a couple reasons and most don't have anything to do with the edge of the reflector, or at least very little-
1. Heat- any closer and I'd have a nice soup dinner. Reflector plays no part
2. Light Distribution- In my tank I'd like the light to as bright as possible at the edges- closer and it turns into a spot light effect, dimmer at the edges- reflector plays some part but the distance from edge to bulb doesn't matter. The light dispersal does though.
3. Water splashes- I am currently running a high flow SPS system in my MH lit tank- The tank is turning over 135x per hour, and sometimes splashes occur in the turbulence. Don't want to risk breaking glass, or worse electrical shorts etc.- nothing to do with "using as a reference point the bottom edge of any given reflector, because that's the factor that we use when we judge the distance from the waterline (or above the tank frame) to mount them."

Most people I know have their T5's really close to the water- 1"-4"
Most people I know have their MH at least 6"- 8" from the water and many even more...

I guess we'll just have to agree to disagree then, because I don't think that any other information is as useful as knowing how much light is hitting the bottom of a tank with the MH and T5 at a realistic and common distance from the tank edge. Trying to make them equal is not important.

[thriceanangel]

As far as the chiller is concerned, that would be another variable that we can eliminate- or just test at the height which someone with a chiller would have their fixture. Valuable to those with chillers and MH.