You are not flawed. photons are photons, and the more evenly distributed these photons are, and the more they are all focused in the same direction, the better they will penetrate. OTOH, the 400s will have peaks that are much higher as you get close to the bulb. T5s tend to peak out at about 1000 PAR as you get within 3" of the bulb/reflector. Im sure a 400wattSE in a lumenarc has a much higher peak. According to Sanjay's tests of the lumenarc3, he will have peaks of about 2500 at about 6" away from the reflector...
http://www.advancedaquarist.com/issues/mar2003/feature.htm
Which makes sense, since 400watts of light in a much smaller area will mean more intensity as you get closer to the bulb. The T5s mave all that wattage spread out over all those bulbs, each being about 8-10x the surface area of the inner halide.
The halide is more of a point source, and the T5 is more linear. Im not going to say that the halides are a 'point source' 100%, but more of one than the T5s would be. Some say that linear lights over a square aquarium result the same light intensity from top to bottom. According to theory, this is true. The light that is going downward from the bulbs, evenly across the tank, would reflect off the glass, etc.... from top to bottom. It is in theory very possible, but only with a morrored glass box and no rockwork inside. Water itself absorbs light as well. The halides are not exactly a point source, but they are only 18"x18" squares of light. And although the reflector helps gather and focus that light, it doesnt aim it all downward like an LED, alot of light escapes at radiating angles w/o ever making it to the water. The reflectors are also working with light that is reflected, as in, the light has to travel from the bulb to the reflector in the first place. So while wider reflectors help offset the inverse square law for halides, they arent 100%.
Both are somewhere in between. T5s prolly penetrate better, and are spread out better, but their output hardly penetrates without weakening with depth. The halide bulbs themselves might be point sources, but the reflectors helps offset that some. Still, the reflectors are only what... less then 1/4 the surface area of the whole tank? They may not be point sources, but they will be more so than the T5s by a large margin.
What this means to us... Shadows are the best way to tell how much a light is a point source. You like 'shimmer' lines? Well, they are a result of using a point source for lighting. The more you distribute the light over the top of the tank, the less shimmer you will get. The more shimmer you have, the more like a point source your lighting really is, and the less the ligth penetrates. If you hold your hand, or some other object in the tank at various levels, you can determine what the distribution/penetration is by how large/small the shadow is underneath that hand. Examples? My 40B with a lumenarc DE has NO shimmer lines despite it being a halide... the reflector covers too much area for shadows to be cast. If I mounted the halide taller, or used my old PFO mini-pendant, the shimmer would increase, and so would the shadows... so it would be more of a point source. On my T5 tank, I have to hold my hand about 6" from the bottom or less to even get a shadow from it... the T5s are able to send light from so many angles.
Sanjay's halides will give him greater peaks near the bulbs. This may be necessary for some corals. I have some Millipora varieties that dont seem to color-in unless they get about 2000 PPFD on their tips. I wouldnt be able to keep it colored in under T5s most likely (yet oddly enough, within 6" of the T5s, this coral's frags are coloring in even more intense than 6" right under a 250wattDE halide). Since using the lumenarcDE, this milli has lost some color. The lumenarc makes more light across the whole tank, but it isnt able to concentrate the output of the bulb as well as a smaller reflector close to the bulb, like the PFO mini-pendant I had on the tank before. But for most corals, they dont need that much. The T5s would allow more light across the rest of the tank, and allow for more medium-high light corals to be placed anywhere in the tank. With 400watt halide pendants, that 2500 PAR is higher than most anything really wants or needs (except for that pink milli of mine), and even at that, Sanjay would only have that much light in very small patches located right under the bulbs. Putting corals here would block out light to other places in the tank. FWIW, I remeber someone saying that getting close to some 250watt halides produced outputs that were higher than found at the ocean surface... so 400s are beyond that. T5s would penetrate better, and although not peaking as high as the 400s close to the bulb, these levels arent really useful for anything anyways. The light from the T5s at the bottom of the tank would be more even, and brighter than the halides (provided quality reflectors and active venting are used for the T5s).
Not trying to turn this into a T5 vs halide argument, so I'll rephrase it this way... Lets say that Sanjay were to use 1600watts in 175watt halides. Thats about 10 halides, in lumenarc3 reflectors. Same wattage, but now the light would be spread out over 80% of the tank's surface. Now, while getting close to one of these bulbs would not yeild the same peaks that getting close to a 400 would, those peaks might not be needed, and the light coming from all those different angles and areas would mean more light makes it to the bottom of the tank and around every rock in the tank with the 10 smaller halides rather than the 3 larger ones. Only 3 bulbs over a 28 square foot tank means alot of shadows. But that also means more 'shimmer', and more shadows, etc. The 'look' in the end it what matters.
And nobody wants to replace ten 175watt Bulbs every year though rather than three 400s. Thats something like $700 in bulbs every year. Three 400s cost at most $450 if you get the high-pressure ones, but more like $300 for most. 28 x T5s would cost about $280 per year to replace... since most T5s except actinincs will last for 2 years, but this is offset by by the average cost of many daylight bulbs being much less than the $20 per bulb average).
I should have tried to get a sponsored tank like the NASCAR race cars, and have offered to put thier stickers all over the tank and over myself when I give talks. :eek2: 
that are also significant cost elements of having a reeftank. 
