Halide lights compared

Hello again. Amongst my reading I have encountered an article about Metal Halide bulbs and how they compare to each other. I have learned not to trust the manufacturer when it comes to Kelvin rating of each bulb. I am going to jot down a couple things that will hopefully help everyone ask the right questions when considering a Metal Halide bulb. The article is from a 2002 issue of Marine Fish so it does not have the new bulbs.

First of all, the light that we can see rests between 380 and 770 nanometers. Light on the lower end from about 310-400 nm is UV-A. The lower the number, the more energy the light has. Therefore, a blue light with a rating around 450 can travel deeper into the water than a red light with a rating around 675 can. This raises a question for me: Since lower nm of light travel deeper into the water, does UV-A affect our corals positively or negatively? HQI bulbs do not have a UV filter on them but Spacelights have UV filtered glass beneath the bulbs. Is it because the livestock in our tanks is closer to the surface of the water? Or is it not needed?

Another interesting piece of information is that Kelvin rating for Metal Halide bulbs is a guess. The term "blackbody radiator" is used to define the color temperature of any bulbs. The blackbody radiator is a theoretical object that is a perfect radiator that absorbs all light incident upon it. In order to properly assign any bulb a color temperature, the bulb must closely resemble the blackbody radiator in spectral power distribution (spd) curve and chromaticity (color appearance). Well, Metal Halide bulbs do not have a SPD close to that of the blackbody radiator so Metal Halide bulbs are given a correlated color temp (CCT) rating. A bulb with a CCT rating implies that it matches the chromaticity but not the SPD of the blackbody radiator. I am still trying to fully grasp this concept from what I have read it appears that there are some assumed lines of color that are used to rate Metal Halide bulbs. Incandescent bulbs have a SPD closest to that of the blackbody radiator so their color temps are the most accurate. Another term used is CRI, which is the comparison of a bulb's temp to the blackbody radiator. So for example, an incandescent has a very high CRI, almost 100, so its color is pretty accurate. If another type of bulb had a CRI of 60, then its assumed color temp MAY not be completely accurate.

OMG, this is going to be long. I have to take off for a bit, but I will get into the different bulbs when I get back. For legal purposes, I do recommend that everyone buy a copy of Marine Fish because its a great magazine. There, I've wrote my disclaimer.

Hey, I have 400's .  I guess I'll have to buy the magazine . 

Thanks , any idea where Ushio's come in?

Have you read these on-line articles?

Effects of Narrow Bandwidth Light Sources on Coral Host and Zooxanthellae Pigments
http://www.advancedaquarist.com/issues/nov2003/feature.htm

SPECTRAL ANALYSIS OF 150W DOUBLE ENDED METAL HALIDE LAMPS AND BALLASTS
http://www.advancedaquarist.com/issues/nov2002/feature2.htm

SPECTRAL ANALYSIS OF RECENT METAL HALIDE LAMPS AND BALLAST COMBINATIONS
http://www.advancedaquarist.com/issues/oct2002/feature.htm

Lighting the Reef Aquarium - Spectrum or Intensity?
http://www.advancedaquarist.com/issues/feb2002/Feature.htm

ANALYZING REFLECTORS: PART I – MOGUL REFLECTORS
http://www.advancedaquarist.com/issues/mar2003/feature.htm

Analyzing Reflectors: Part II - Double Ended Lamp Reflectors
http://www.advancedaquarist.com/issues/july2003/feature.htm

The Static on Static Lighting:
Suggestions for Better Lighting Applications of Photosynthetic Reef Organisms -
Moving Light Systems (MLS)
http://www.advancedaquarist.com/issues/oct2003/feature.htm

The Properties of Light
http://reefkeeping.com/issues/2002-03/atj/index.htm

Lighting the Reef Tank: A Primer for Beginners
http://reefkeeping.com/issues/2002-08/dw/index.htm

plus a bunch on animalnetwork that I can no longer reach...

Jon, no I have not had the opportunity to read those. Maybe you could give an overview like I've done.

Travis, I would get the CCT & PPFD ratings on the bulb from the manufacturer.

I have 2 Aqualine Busch 10k

bulbs for sale but I want more for them than you can buy new cheaper brands for. But I think this shows their worth it.

The last test was on ballasts. The three ballasts that were tested are PFO magnetic and electronic and Aromat electronic. All three were tested using a 150 HQI Aqualine Busch 150 watt bulb. Each bulb in all the tests were burned in for 100 hours prior to testing and warmed up for 20 minutes before the tests were performed. I also failed to mention that above tests were done 18" from the sensor and without a reflector and in a dark room. This test was also 18" from the sensor but with a PFO reflector and a UV shield. The PPFD ratings of this test are higher than the "naked" 400 watt PPFD so it shows what a good reflector can do.

PFO Magnetic 246 PPFD & 10147 CCT & 1.64 amps
PFO Electronic 210 PPFD & 9921 CCT & 1.4 amps
Aromat Electronic 209 PPFD & 10157 CCT & 1.4 amps

I do not know how the wear and tear on the bulb differs from electronic to magnetic ballasts.

There you have it folks. I hope this helps. I also again give all the credit to Sanjay Joshi who wrote the article for Aquarium Fish in their 2000 Anniversary issue call Marine Fish & Reef.

Awesome link, ssilcox. I am interested to see how these XM's do in the long run. I think its amazing to see the difference in PAR and PPFD with electronic versus magnetic ballasts.

Good, bad, or okay is a matter of opinion.

The PPFD of 123.7 is very good compared to the ones in my magazine except the Iwasaki. The Iwasaki has a PPFD of 186 and a CCT of 7660. So the color is almost the exact same from the 6500 K Iwasaki and the 10000 K Ushio but the Iwasaki puts out more power. But the link that Jon posted doesn't say what kind of set up is being used to test the bulbs. The test in my magazine are without a reflector, in a dark room, and 18" from the sensor.