Um, davejnz...you just proved my point with that listing of FACTS. The first two facts are true of any linear phosphor bulb. The third is something I brought up as well...sure 95 degrees is the optimal temp, and anything above or below this can result in diminished output. Ok, no problem there.
Now the part of "There is a 10% drop in luminous flux when temp is increased from 35C/95F to 48.5C/119.3F". Sure, exactly why I am questioning the longevity of bulbs running on IC ballasts...they are known to run the bulbs hotter.
But where you lose me is on your conclusion part..."The OPTIMAL performance and LIFE of an overdrived T5 can still be attained if the cold chamber can be kept at rated temperature(95F)".
What does instant start or soft starting a bulb have to do with the running temp of the bulb? Once the bulb is started, all that means anything is the operating temp of the bulb...which has nothing to do with the starting mechanism of the ballast or the bulb.
And oops, yeah, I forgot to re-paste that part I deleted. Creative it is...
For now though, I will talk with dwdenny...and deal with one thing at a time...
Linear bulbs will beat point source ones in penetration. Did you catch what I said before? Yep. Im not pullin stuff out of my @$$. If you look in Sanjay's lighting update thread, I even asked him to confirm it while I was looking for the info elsewhere....
"If you have a point source of light, (a source is approximated by a point source if the distance of measurement is greater than 5 times the size of the source), then you can assume light follows the inverse square law.
According to the inverse square law, the intensity of a point source of light decreases inversely as the square of the distance from it. So if you were to double the distance the light intensity would drop to 1/4 of what it was.
A MH has the light source size of about 1.5-2", whereas a 4ft FL lamp has about 4ft of light source. So to really measure a 4ft FL as a point source you would have to be about 20ft from it.
Measuring FL lamps is kind of tricky at short distance.. since the light source is quite long. A FL would spread the light over a larger area. So if we assume we have a FL lamp and MH lamp generating the same number of photons/sec, they would be spread very differently, resulting in very different values of PPFD if single point reading was taken. I have not found an easy way to compare the FL with MH that I feel would be acceptable to the reefing community. Hence I have not ventured into testing FL lamps. The best caparison in my book would be to compare the output of FL lamp fixtures, in a manner similar to what I did with reflectors. Since what we really want is the spread distribution.
On a 4 ft fixtures, this woould mean collecting even more data points than what I did with the MH reflector using a 3ftX3ft grid, and several (6-8hrs) of just data collection if we go with larger grid. It would need a whole new setup and hell of lot more time than I am willing to put into it right now.
I did test some 2ft T-5 fixture from Sunlight supply..... to see that result come to WMC It will eventually get written up, but for now its only available in my talk."
-sanjay.
The bottom line is that halides diminish at an inverse square rate, and linear bulbs diminish in output at a linear rate. Think about it. As you move away from a point source, the photons that it emits spread out in a circle/cone/etc. As they spread, they diminish at a geometric rate. Now, for a linear bulb, the number of photons from any single point would diminish at the same rate, BUT, there is overlap. Imagine going towards the bulb, and you are at one end of that bulb....as you get closer to the bulb, less light from the other end of the bulb reaches you, right? So as you move farther from the bulb, you get more photons from other places on the bulb. So at some point, the percentage lost as you move away from a halide tank will be greater than with the T5.
Now, at that, I think you might be reading more into what I am saying that what I really said. Halides/point source bulbs do have an advantage in other areas. When I say that T5 penetrates better than halide, that also means that the closer you get to halide, that much more the light will get compared to T5. The closer you get to T5, this isnt the case. I can move some of my light loving SPS as close to a T5 as possible, but they just cant get enough light. Why? Well, the closer they get to the bulb, the less of the bulb's output they are being exposed to. Even adding more bulbs can only do so much, as the PAR per square inch of bulb doesnt really change no matter how many bulbs you add. But with halide, the PAR per square inch does increase as you get closer.
The height of the fixtures relative to each other means very little as you can see. Halides do have the advantage of peaking at a much higher level as you get closer to the bulb. This is key for many species of light loving SPS. Then again, the linear output sometimes counters this in that it can prevent shadows and get more light to the entire surface of the coral...but even so...there is only so much intensity that T5s can have as you get closer to the bulb.
But once and for all...yes, T5s penetrate better than halides almost any aquarium (unless you go over 48" or something...lol).
