[SKRIZ]

I still don't get the big deal with DE bulbs! Why would you go with a DE setup over a SE setup.

It seems to me that the light spread is lower, PAR is lower & they consume the same energy.

So why DE over SE?

[Poseidon]

Where did you get this information that is the exact opposite of what I usually hear?

[dougc]

In terms of pure PAR, a DE bulb has no advantage over an SE bulb. It's is the reflector that makes a difference. The DE bulbs are skinnier, which makes it easier to design a more efficient reflector. This is the same thing that makes T5 flourescent bulbs better than T12s.

My personal experience is that an enclosed pendant, in which most DE bulbs are housed, throws less heat into the tank than a typical retrofit SE setup. My Sunlight Supply fixtures vent heat from the top of the fixture, which may account for this.

MH bulbs also apparently run better when hot. Again, the enclosed nature of pendant fixtures aids this.

[Ninong]

Back in 1998 and 1999, Dr. Sanjay Joshi began publishing the first of a series of articles on the results of testing he performed on selected metal halide lamps used in the reefkeeping hobby. These articles, being the first of their kind at the time, were influential in popularizing 250w double-ended 10,000K HQI lamps in the U.S. They were already quite popular in Europe but less so over here.

In this article Sanjay Reported much higher PAR for the Ushio 250w 10,000K HQI DE lamp than for any of the mogul based 250w lamps tested for that article. In fact, he reported higher PAR for this lamp than for several other popular 400w mogul base lamps in use at that time. He also remarked on its excellent spectral distribution qualities compared to other lamps.

More recently Sanjay has reported test results that do not always match his earlier tests. He has also begun testing with more than one brand of ballast and the results for individual lamps can vary substantially depending on the ballast used.

From personal communication with Sanjay, I learned that the unnamed 250w 10,000K HQI DE lamp that he reported on in glowing terms back in 1999 was a Ushio brand. Actually, Ushio of Tokyo makes no lamps for the aquarium market in Japan. ALL of their metal halide lamps for the aquarium market are manufactured in their BLV factory just outside Munich. Both directors of BLV are Japanese nationals. This is why I find it strange that Sanjay got such different results in his most recent testing of the 250w 10,000K HQI DE lamps that were branded Ushio and those that were branded BLV. Both are made at the same plant and are supposed to be identical except for the name. This same BLV factory makes lamps under other brand names for at least two or three other vendors. This is why I find it strange that the test results for some of these different brands of the same lamp are so different. Perhaps this is the result of the expected manufacturing variance?

I can only repeat something that Sanjay told me four or five years ago when I asked him about this in an email. He said we should always bear in mind that he was testing only one sample lamp and that normal manufacturing variances could result in differences of as much as 20% from one sample to another. A more reliable test would require at least 10 samples of each lamp and 10 samples of each ballast, something that would be cost prohibitive. Sanjay also pointed out to me back then that his 1999 test of 250 watt lamps was run with the same standard magnetic ballast for all of the mogul base lamps and a standard HQI ballast for the double-ended lamp. All of those lamps were tested the same 18" distance from the sensor and all were unshielded. More recently Sanjay has tested double-ended lamps with and without tempered glass UV shields because UV shields are a necessity with double-ended lamps. Many lighting experts recommend UV shields for ALL metal halide lamps, both DE and SE.

There are other things that you should be watchful of when reviewing Sanjay's test results. Pay particular attention to the CCT numbers, unless you're looking at 20,000K lamps which have no measureable CCT numbers because they're too monochromatic. I have been looking at his test results for the various 250w HQI DE lamps and I have been surprised at the wide range of CCT numbers he is reporting for the different brands and various ballasts. It's surprising that lamps advertized as 10,000K are producing CCT numbers that range from 7200K to 12000K depending on the brand of lamp and the brand of ballast. That's a VERY big difference in appearance.

Do as much research as you can before making a choice but just remember that this subject if replete with conflicting claims from the manufacturers and often surprising test results from the hobby's independent researchers. The Kelvin ratings assigned by the manufacturers often bear little resemblance to reality. Iwasaki's 50,000K 150w medium base lamp is certainly a nice color but it's not as blue as any of the 20,000K lamps or even some of the 14,000K lamps. In fact, some of the 14,000K lamps are bluer than the 400w Radium 20,000K lamp. And the Venture Sunmaster 1000w 6500K lamp is much, much whiter than any other 6500K lamp on the market. In fact, it is whiter than many 10,000K lamps. And don't even get me started on the Kelvin ratings assigned to the various brands of fluorescent lamps.