Is there a way to judge k rating by lumens?

[harmonic]

Is there a way to loosely judge k rating by lumens?

If the two are related in any way, there should be a method to compare them and estimate the color temp. of any given bulb based on its lumen rating. As we all know, only bulbs produced especially for the aquarium trade are marked with kelvin ratings. All of the bulbs we use are marketed for other industries as well, and can be purchased at a fraction of the price. These bulbs, however, even if they are exactly the same, are not marked with k ratings, but lumen ratings instead.

If someone could work out a theory it would greatly benefit all DIYers across every facet of the aquarium hobby.

[Ninong]

Originally posted by harmonic:

Is there a way to loosely judge k rating by lumens?

No, they are unrelated. Lumens is a measure of output, Kelvin is a description of color.

As we all know, only bulbs produced especially for the aquarium trade are marked with kelvin ratings. All of the bulbs we use are marketed for other industries as well, and can be purchased at a fraction of the price.

You can usually find the Kelvin ratings for any bulbs from the manufacturer's specifications on their website. If the exact same bulbs that we use could be purchased for a fraction of the price, we would all know about it by now. They are not the same.

These bulbs, however, even if they are exactly the same, are not marked with k ratings, but lumen ratings instead.

They are not exactly the same. You might want to specify whether you are talking about NO fluorescent, VHO fluorescent, power compact fluorescent or metal halide so that we will know what you are asking about.

If someone could work out a theory it would greatly benefit all DIYers across every facet of the aquarium hobby.

If you have a particular bulb in mind, tell us exactly what it is so that we can discuss it. I am not aware of any bulbs, other than a few of the 6500K power compacts, that are sold for general purposes that could possibly be used for a reef tank.

[harmonic]

Originally posted by Ninong

No, they are unrelated. Lumens is a measure of output, Kelvin is a description of color.

Both are SI measurements, and since SI units are defined by prefix multipliers according to powers of 10 ranging from 10x-24 to 10x24, I believe it is not illogical to hypothesize a relationship between them.

You can usually find the Kelvin ratings for any bulbs from the manufacturer's specifications on their website.

Sometimes, yes, if you have the bulb in your hand, or have a specific manufacturer in mind. What about the possible hundreds of light manufacturers around the world we've never heard of?

If the exact same bulbs that we use could be purchased for a fraction of the price, we would all know about it by now. They are not the same.

No possibility that there could be some obscure manufacturer somewhere in the world making a bulb exactly the same as a 400w Ushio that you don't know about? Are you sure?

They are not exactly the same. You might want to specify whether you are talking about NO fluorescent, VHO fluorescent, power compact fluorescent or metal halide so that we will know what you are asking about.

I'm talking about any one, or combination of the bulbs you've listed, plus any other uncommon high intensity bulbs whos' existence may have escaped your all-encompassing notice.

If you have a particular bulb in mind, tell us exactly what it is so that we can discuss it.

Thanks anyway. If the discussion follows the tone of your reply, I don't want any part of it.

I am not aware of any bulbs, other than a few of the 6500K power compacts, that are sold for general purposes that could possibly be used for a reef tank.

I understand that certain types of lighting are better suited and more desirable for use on a reef tank due to their radiant intensity, but that does not mean that other lighting solutions cannot be utilized with some degree of benefit.

[Ninong]

Originally posted by harmonic:

...there should be a method to compare them and estimate the color temp. of any given bulb based on its lumen rating.

Sorry, but they are not related at all. That's like saying that a red car is faster than a blue car because of the color or that we should be able to estimate the color of the car based on the horsepower.

As we all know, only bulbs produced especially for the aquarium trade are marked with kelvin ratings.

No, we don't all know that. As a matter of fact, most metal halide bulbs are Kelvin rated, whether they are marketed for the aquarium trade or for architectural display. If they are marked blue or green or magenta, it just means that they are too monochromatic to determine a meaningful Kelvin rating. This does not, however, prevent people from calling Radium's "blue" metal halide bulb 20,000K. Radium simply calls it "blau" (blue). The ones with Kelvin ratings of 3500K, 4000K or 4500K are unsuitable for reeftanks.

Most of the lighting industry’s customers use lamps for satisfying human visual needs for illumination, which is why they advertise the lumens. Lumens is a quantitative measurement of visible radiation (380-770nm) with a sensor having a spectral response curve equal to that of the human eye. The human eye is not especially sensitive to those wavelengths known to promote photosynthesis (violet, blue and red). We are not really interested in luminous flux for reeftank lighting. We need to know the photosynthetic photon flux density (PPFD) because this is a measurement that is meaningful to photosynthetic symbiotic algae. PPFD is a measurement of PAR (photosynthetically active radiation) in a spectral range from 400-700nm. This is why 6500K metal halide bulbs appear so intense to the human eye -- our eyes are extra sensitive to green and yellow and much less sensitive to blue and violet.

The only quantitative measurement that is meaningful for a reeftank is the amount of PAR a particular bulb produces. The qualitative measurement that is important for a reeftank would be the Kelvin rating, assuming it is accurate and assuming the spectral distribution is not weird. This is not to say that one particular Kelvin rating is better than another for all purposes, but at least it provides meaningful information upon which the aquarist can base his decision.

Some 175w metal halide bulbs produce four times as much PAR as other 175w metal halide bulbs, so knowing the PAR rating is extremely important in choosing the best bulb.

If you are talking about Kelvin ratings on fluorescent bulbs, then I'm afraid they are in a class of their own and mean whatever the marketing department thought would help them sell better. The designation of 7100K on certain "blue" power compact fluorescent bulbs means absolutely nothing. It is a number taken out of thin air. It has no meaning at all. The 9325K GE fluorescent produces a pink glow in the aquarium. The 10,000K URI fluorescent bulb used to be called something like 5500K before they decided that 10,000K sounded better and might sell more bulbs. It is the same Aquasunlight bulb that it was before they decided to advertize its Kelvin rating as 10,000K instead of 5500K. There was absolutely no difference in the bulbs, just a difference in the ad copy.

The only reason that some manufacturers call their actinic fluorescent bulbs "03" actinic is because the "03" designation was part of the product code Philips used when they introduced "actinic" fluorescent bulbs on the market and everyone wanted to claim that their product was just as good. The designation "true 03" simply means that the manufacturer wants you to believe that their bulbs are similar to the original Philips normal output fluorescent bulbs that were so well received.

Even with metal halide bulbs, some 10,000K bulbs are bluer than others (some are much bluer) and some 12,000K bulbs are considerably bluer than the Radium 20,000K bulb. And I don't know what to say about Iwasaki's new 50,000K 150w medium base metal halide bulb except that it is nice. You would have to ask them how they determined that it was 50,000K. AB claims that all of their AB-10000 metal halide bulbs are actually 13,000 Kelvin. According to the manufacturer, they used to be 10,000K but they made some changes about six years ago that raised the actual Kelvin temperature to 13,000K, but they decided to keep the same model designation. So the AB-10000, according to AB, is actually 13,000K.

No possibility that there could be some obscure manufacturer somewhere in the world making a bulb exactly the same as a 400w Ushio that you don't know about? Are you sure?

Sorry, I assumed you had something particular in mind. So far no one has found a cheap replacement for the 400w Ushio 10,000K bulbs unless you want to count some of the Chinese imports of dubious reputation that are sold to the aquarium trade for practically the same price. If you find something, tell us what it is so we can discuss it. I would be surprised if you find something that hasn't already been discussed on the various reefkeeping boards, both here in the U.S. and in Australia, the U.K., Canada, Germany, France, Hong Kong, Japan and Austria. I'm sure there are others, but those are the countries whose boards I browse from time to time thanks to online translator software.

I'm talking about any one, or combination of the bulbs you've listed, plus any other uncommon high intensity bulbs whos' existence may have escaped your all-encompassing notice.

There are quite a few HID spotlight fixtures sold in Hong Kong and Japan for the aquarium trade that are not marketed in the U.S. but none of them are cheap. All of the cheap lamps sold in the U.S. are not suited for reeftanks because they usually have a very uneven spectral distribution shifted to the red end of the range, but they make nice growing lamps for indoor crops.

I understand that certain types of lighting are better suited and more desirable for use on a reef tank due to their radiant intensity

No, it's not due to their radiant intensity unless you are using that term in the sense of value for the money, as in a 400w 6500K Iwasaki bulb is cheap ($60) and produces lots of PAR. As far as intensity is concerned, you can always add additional bulbs or move up from 150w to 250w to 400w to 1000w, etc.

All of the cheap solutions that have been proposed on the various bulletin boards have proven to be unacceptable for various reasons.

[Newreefer]

Some companies will us a CRI or color rendition index of each bulb to explain the colour. The closer a bulb is to natural light the higher the CRI index. The lower the Kelvin is on a bulb also translates into a lower CRI index. Once you go over 10,000 K or 12,000 K in some bulbs the light becomes too blue and the CRI goes down again.
There is a really interesting article in Online Aquarium Magazine from 2002 (not sure which month) but they did tests on the PAR value (usable photosynthtic light for coral growth) for different bulbs. One was a $20 home depot bulb another was an expensive aquarium bulb. The PAR values were very similar. The article goes on to explain that the more expensive bulbs don't benifit the corals but are more of an astetic value to the user. Higher K bulbs are more white/blue then cheaper lower K bulbs which are yellow.
You can go the cheaper bulb route and then invest in some VHO actinics to even out the spectrum to a more white/blue colour.

Personally I am running Ushio 10,000K bulbs right now but when they get changed next year I will go for 5,500 K Ventures. Some friends of mine use them with VHO actinics and the coral growth is fantastic with amazing colours in all sps. The tanks balances out with a nice white/blue colour.

Another asside from this is that the lower Kelvin bulbs produce more UV light. (from the GE web site) This would explain why some sps's turn nicer colours under lower K bulbs, since there colour is a form of suntan from UV light.

Hope this helps. The lighting misconceptions in this hobby have confused me for a long time.

Oh yes, last note. There are not that many bulb manufacturers in the world. A friend works here at a huge wholesaler of light bulbs and fixtures and there are only a handful of makers. Example: Ushio makes all the Hamilton Bulbs.

[Ninong]

Originally posted by Newreefer:

Example: Ushio makes all the Hamilton Bulbs.

And they are made in the BLV Licht und Vakuumtechnik GmbH plant just outside of Munich. BLV is a wholly owned subsidiary of Ushio. And they are branded Ushio, BLV, RedSea and at least one other brand name besides Hamilton.

Personally I am running Ushio 10,000K bulbs right now but when they get changed next year I will go for 5,500 K Ventures.

Before you do that, you might want to read this article: http://www.personal.psu.edu/faculty/...omparison.html

You will notice that Dr. Joshi tested the 175w Ushio 10,000K lamp vs. the 175w Venture 5500K lamp and found that the Ushio produced three times as much PAR as the Venture. A 5500K lamp may seem bright to our eyes, but our eyes are deceiving.

(P.S. -- Here is an interesting article that describes the absorption of differing wavelengths per meter of water: http://www.reefs.org/library/talklog...wn_060798.html )

Another asside from this is that the lower Kelvin bulbs produce more UV light. (from the GE web site)

In general, this is not true of metal halide lamps. I wonder what lights GE was talking about? As you can see by a comparison of UV photon units in this article, the 400w GE 6000K lamp measured 9.62 vs. 13.56 for the 400w Iwasaki 6500K lamp and a whopping 23.22 for the 400w AB 10,000K: http://www.animalnetwork.com/fish2/a.../1/default.asp

Some companies will us a CRI or color rendition index of each bulb to explain the colour. The closer a bulb is to natural light the higher the CRI index. The lower the Kelvin is on a bulb also translates into a lower CRI index.

If lamp manufacturers could produce a perfect lamp, which they can't, then a lamp of 5500K would have a CRI of 100 and anything with either a lower or higher Kelvin rating would have a lower CRI number. The problem is that lamp manufacturers cannot produce lamps that correspond exactly to a given color temperature of a true black body.

The CRI index just tells us how much a given lamp will cause an object to shift in perceived color compared to its color under natural light. An index of 100 would mean that the color of an object under that light would appear to us exactly the same as it would under sunlight at noon. For reefkeeping lighting, a higher CRI number does not necessarily mean a better lamp. Remember that nothing under water appears the same as it does at the surface. To further complicate matters, most lamps do not correspond to the spectrum of any true color temperature -- which is why they give you the CCT (correlated color temperature), a calculated value approximating the closest true color temperature.

The spectral distribution of a given lamp is the most important information that we need in choosing reef aquarium lighting. Metal halide lamps have strong peaks superimposed on a smooth background spectra and in order to understand what's going on we need to know the quantities of light at each wavelength.


P.S. -- Here is a very interesting article on UV radiation in reef aquaria by Dana Riddle: http://www.aquarium-design.com/reef/uvlighting.html

Here is his conclusion:

Review

These short articles have shown that all the lamps we tested produced UV radiation. Metal halide lamps’ outer glass envelopes only weaken UV; they do not eliminate it. The actual amount of UV produced by a metal halide lamp depends upon many factors such as lamp wattage, lamp orientation and arc tube construction (universal burn position versus bottom up or bottom down). Profound differences can exist between “identical” lamps. More importantly, the shape (along with the type of reflective surface) can focus UV energy into “hot spots” where the UV energy exceeds that found in nature. Even higher UV energy is produced during lamp strike and water surface waves can further focus this radiation. Seemingly small differences (such as lamp height) can also have a major impact upon the amount of UV entering an aquarium. With so many variables involved, it is difficult, if not impossible, to know how much UV is being produced without actually making measurements.

We have seen that UV radiation has the potential to damage corals and other coral reef inhabitants. Many reef animals can produce natural sunscreens (MAA’s) to protect themselves against UV but MAA concentrations are possibly a response to the amount of UV to which they are subjected. This is an important point since UV production among all tested lamps was not consistent and can change dramatically during normal operation or when the lamp is changed.

Our experiences suggest that coral coloration is a response to PAR levels, not UV. In short, we find no reason to subject reef aquaria to high UV levels.

[RadioPlay]

Hey Ninong,
Sorry to bring back this thread but I just had some light ??? I have 4x55 PC lighting my 60g aquarium and I'm looking for replacement bulbs. In this thread you commented that for PC lights temp(K) has really no meaning. So if I go for 6700K or 10000K replacement bulbs there would not be any difference on coral/algae growth. If that is the case why would they price 10k bulbs more, is it just a marketing scheme. Thanks

Ryan

[Ninong]

Hey Ninong,
Sorry to bring back this thread but I just had some light ??? I have 4x55 PC lighting my 60g aquarium and I'm looking for replacement bulbs. In this thread you commented that for PC lights temp(K) has really no meaning. So if I go for 6700K or 10000K replacement bulbs there would not be any difference on coral/algae growth. If that is the case why would they price 10k bulbs more, is it just a marketing scheme. Thanks

Ryan

Ryan,

Kelvin ratings are misleading and that is true of virtually all of the various different lamps available for use in the hobby. In particular, the rating of 7100K for "blue" PC fluorescent lamps is a number that means absolutely nothing. There is no rational explanation for that number. Just looking at it you would expect that it would have an appearance between a 6700K lamp and a 10,000K lamp, yet it is supposed to be an actinic lamp and it, in fact, has most of its output around 450nm.

Even the well regarded URI VHO fluorescent lamps have undergone marketing-inspired changes in their Kelvin rating numbers that were not accompanied by any actual change in the lamps. URI just decided that 10,000K sounder cooler than the previous much lower number. So the AquaSun is now supposedly 10,000K and the ActinicWhite is 12,000K. At least they do not try to put a number on the SuperActinic lamps.

When it comes to metal halides lamps, there is a great deal of confusion. Just consider that Iwasaki has a 150w medium base lamp that they claim is 50,000K. Or how about all the 12,000K lamps that are much bluer than other 20,000K lamps.

Getting back to your exact question, you could choose either 6700K or 10,000K PC fluorescent lamps but my personal preference between those two options would be the 10,000K. In general, a 10,000K PC fluorescent lamp will be whiter than a 6700K PC fluorescent lamp by the same manufacturer.

[RadioPlay]

Thanks Ninong! So for the most part the Temp is more for appearance than for actual coral growth? Or am I wrong on saying that?

Ryan

[Ninong]

Thanks Ninong! So for the most part the Temp is more for appearance than for actual coral growth? Or am I wrong on saying that?

Ryan

Ryan,

It's not that simple. I'm trying to figure out how to explain this in a few sentences and the truth is that it can't be fully explained in anything less than a few thousand words. And I'm not up for that right now.

Photosynthetic corals depend on their symbiotic zooxanthellae for most of their energy requirements. The zooxanthellae depend on their pigment system to utilize photosynthetically active radiation (PAR) to power photosynthesis. Not all wavelengths are equally important in this process, some spectra are more active than others. It's even more complicated by the fact that the various pigments utilize different parts of the spectrum.

In general, corals at greather depths have adapted to the blue-green light found there and corals near the surface have a different adaptation. But the same species can be found at a wide range of depths because its zooxanthellae can compensate for reduced light by enlarging the size of their PSU's (photosynthesis units). So, yes, color temperature (Kelvin rating) is important. But so is intensity.

If that sounds like a lot of contradictions that's just because that's the way it is. We usually simplify things by comparing PAR ratings of various metal halide lamps but even that is misleading in that the 'quality' of the the PAR may not be equal. You need to also know the spectral distribution to make an informed comparison.

This doesn't even begin to cover this topic. Lets' just say that you cannot say that color temperature is just for appearance.

[RadioPlay]

Ok Ninong now that you have my head spinning I know that my 'appearance' claim was a pretty ignorant statement to make, unfortunately as a newbie reefer I'm still trying to learn all the details as I go along. As I stated earlier I'm working with a 60g which is a habitat for softies, LPS and a few fish. I would like to purchase bulbs that would be best for my LPS and good coraline growth. My lights consist of 2 daylights and 2 actinic. So.... yeah that's about where I'm at.....pretty pathetic huh?

I'm beginning to understand the spectrum and how the different temps affect different corals at different depths, I'm just not sure how to determine what is best for my small 60g. Thanks for your patience with us ignorant fools.

Ryan