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View Full Version : Not stirring the pot but just a question...


jamesbm1001
07/09/2009, 10:35 PM
Okay, so I've been searching all of the boards, and haven't found it so if it's been addressed and I missed it I apologize, but is there a reason that mercury vapor lamps aren't used? In searching for a new lighting scheme I've considered everything. One thing I happened across was the fact that these bulbs have long life, good output, and are cheap. Also, they seem to have a good color spectrum as one article which I can't remember stated the output was dominant between 350nm and 500nm. I'm sure there is good reason that no one uses them, I just couldn't find it. I'm not really interested in the heat/light spread that is covered by the many t5 vs. mh discussions, but more MV vs. MH, that being said all replies/comments/thoughts are welcomed.

ginger7286
07/10/2009, 09:04 AM
hummmm, not sure because I don't use them but maybe because of the Mercury in them? Could an environmental thing. How long do they last before they need replacing and do they require any special disposal?

DarG
07/10/2009, 09:27 AM
Most range in color temp from about 3000K - 6500K. In other words, they create a yellow look to the tank. Every seen a 6500K halide lamp over a tank? They are color corrected with a phosphor coating to create a whiter output but I believe that there is a high amount of output in the red spectrum because the phosphor coating is heavy in the red because the lamps are heavy in the UV range on their own, without the color correcting phosphor coating. I dont know if you can find non phosphor coated MV lamps. And if you could, I believe that the non corrected spectrum lamps would be too heavy in the UV range to be appropriate for lighting a reef tank and probably for viewing as well.
They are actually fairly similiar to metal halide lamps which also contain mercury. Not in raw spectrum but in design ... they both have a central arc tube, etc.

Im sure that PaulErik would have lots of details on MV lamps. The info I have is on them is from memory from looking into them out of curiosity years ago and may not all be accurate.
But the general conclusion was that they werent suitable for reef tank lighting.

jamesbm1001
07/10/2009, 09:43 AM
The UV issue was one that I had considered. I can't be sure but I seem to remember reading at one point that the older Iwasaki 6500K bulbs were in fact mercury vapor bulbs. As far as the appearance being yellow/red, I thought that the inherent appearance of a non-color corrected bulb was very blue, which is terrible for commercial lighting because it makes people look gray/bloodless. This is just a fact finding mission because I don't know, I doubt I'd use these bulbs but I have an over active curiosity about lighting and all the possibilities.

ackee
07/10/2009, 10:33 AM
These are the kind of bulbs that you may have seen atop tall aluminum shafts in various parking lots, toll plazas, etc., giving off a garish mustard yellow light. They must be cost effective, because nothing that ugly could otherwise be justified.

jamesbm1001
07/10/2009, 11:00 AM
I think what you're thinking of are High Pressure Sodium bulbs, but I could be wrong

jamesbm1001
07/10/2009, 11:02 AM
agreed with the price being the only way to justify the look though:D

ackee
07/10/2009, 02:31 PM
You're right, of course. Sodium high pressure lights are what I had in mind.
Do you think, though, that the uncorrected natural color of sodium hp lights is blue, and that for some reason that color was modified to diaper yellow? Maybe the original blue proved unflattering to state troopers and toll collectors.
It probably has something to do with visible light spectra, another example of human self-centered thinking. What about racoons and field mice? They may see things differently.

jamesbm1001
07/10/2009, 06:13 PM
HA! I think I'll start a petition on behalf of racoon's and field mice everywhere.

DarG
07/11/2009, 06:00 AM
<a href=showthread.php?s=&postid=15335990#post15335990 target=_blank>Originally posted</a> by jamesbm1001
The UV issue was one that I had considered. I can't be sure but I seem to remember reading at one point that the older Iwasaki 6500K bulbs were in fact mercury vapor bulbs. As far as the appearance being yellow/red, I thought that the inherent appearance of a non-color corrected bulb was very blue, which is terrible for commercial lighting because it makes people look gray/bloodless. This is just a fact finding mission because I don't know, I doubt I'd use these bulbs but I have an over active curiosity about lighting and all the possibilities.

Yes. that is what I stated, I thought ... that the NON color corrected MV lamps, those without the phosphor coating are heavy in the UV spectrum which would give a "bluish" or violet (maybe ultraviolet is a better description) or similiar type of appearance. But we are talking about a alot of energy below that of even the super actinic lamps. I dont believe that corals use that low of a spectrum for photosynthesis so those spectrums wouldnt be appropriate for reef tank use. There is some energy higher up as well but from an efficiency standpoint and Im sure, an appearance standpoint, the non corrected MV lamps, I believe, would be a poor choice for reef tank lighting ... again, this is from what info I gathered on them a good while back, all of which is also from memory. So I could be wrong both from the standpoint of what I am recalling about them as well as some of the basic info that I gathered in the first place.