Okay, changing bulbs, why do we really do it?

G

gummyworms

New member
Hello,

I've been searching through the forums, and haven't been able to find a definitive answer on this. We in the hobby change bulbs every 6-12 months, with the commonly cited reason of "spectrum change."

An article recently in reefkeeping.com showed that a phoenix 14K doesn't lose much INTENSITY over the course of a year, or even two years for that matter, so it has to be SPECTRUM which changes.

Correct me if I'm wrong...SPECTRUM is measured in Kelvin? Thus, will a 14K bulb last longer than a 10K bulb due to its SPECTRUM needing to shift "more" to get to that green/yellow/red-ish range which is generally agreed to fuel algae growth and retard coral growth?

A confused newbie,
Shawn
 
I wish I had the answer but I don't. I'm hoping someone will come along and explain. I think your right though. It's just a spectrum shift, not intensity shift.

Regards,

Pat
 
Spectrum shift makes sense, so I will actually see my bright crisp Phoenix 14K blue shift into more of a white/yellow before I have to replace it?

It should be noticeable in color to our eyes right...I mean taking into account that the change happens slowly enough that we might not notice it (we get used to it).
 
I believe there is a shift in intensity as far as PPFD

Photosynthesis photon flux density(PPF, PPFD)
Not energy but unit expressed at the number of the light quantum ( photon ) which is a particle of the light are photosynthesis light quantum flux density. Meaning the amount of light particles falling in an amount of area.

Age PPFD CCT
New 203.7 6637
3 months 202.1 6326
6 months 190.4 6176
1 year 169.2 5800
1 year 166.1 5988
1 year plus 158.3 5939
2 years, 2 months 174.8 5977
2 years, 7 months 143.8 5394

This was a test on a Iwasaki 6500k bulb, CCT being the correlated color temperature, so from these tests it appears there is a drop in intensity.

I may be wrong, its happened before
 
In terms of PPFD, I agree that there is a shift in intensity, but just by itself, a 25% decrease in light shouldn't cause the extreme effects that others point out, should it?...nuisance algae, corals decoloring, etc.

It seems from the other data, the CCT doesn't shift too much either, about 15% after a year, and about 25% after two years. Lets say I have a 14000K MH, after 2 years, following the same trend, it would be roughly 11000K, still far above the yellow/red/green range which is considered bad?

Maybe the higher the Kelvin, say 10K and 14K, the faster it shifts? Maybe 10K and 14K bulbs both shift to 6-7K in a year? That would make sense in terms of causing problems, but I never hear people mention that the bulb color actually changes that much, just that one day, they feel their tank isn't doing so well, and then after switching the bulb, its totally rejuvenated.

I really appreciate your data, just trying to figure out for myself what really is going on which causes us to have to part with so much money each year!
 
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Professional lux meter

Milwaukee Instruments Smart Lux Light Meter


lg_26396_35987P.jpg



Verify light intensity in your aquarium like the pros. Easy-to-use, portable lux meter with waterproof sensor gives a precise reading of how much light your aquarium inhabitants actually receive. Accurately measures from 0.000 to 50,000 Lux with ±6% of reading ±1 digit. Use to determine light intensity in different areas in reef aquariums for ideal placement of corals with different light requirements. Also, a great way to monitor light fixtures to ensure optimum performance. 9V Alkaline Battery included. Measures 3" x 1-3/8" x 5-1/2" high.


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Sunlight Supply Light Meter

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Measures footcandles and lux
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Commercial quality
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Silicon photodiode sensor



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Gossen Color-Pro 3F

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good luck !!!! :-)
 
LUX is not a usefull measure for our purposes. The meters shown above are all but usless in our hobby.

Yes, the spectral output and intensity will shift (degrade) over time. Different bulbs will exhibit different rates of shift and degredation. These shifts will certainly cause a decrease in PAR as well as percieved color and intensity.

Because each bulb and brand are different, it is hard to say at what age a bulb should be replaced. It is also open to debate as to what "level" of output degredation is acceptable.

You can buy the Apogee Quantum meter for a few hundred dollars and take your own readings and make your own decisions.

Bean
 
no

It is both the spectral shift (decay of the phospors) and degraded output (decay of the arc structure and halide).

Bean
 
Temperature

The metric unit of temperature is the kelvin (K). The temperature of an object depends on how fast the atoms and molecules which make up the object can vibrate. As the temperature drops, the vibrations of the molecules become slower. Eventually a point is reached at which molecular vibrations should cease, and this is called absolute zero. Absolute zero is the zero point on the kelvin scale (0 K). Absolute zero is -273.15°C (or -459°F).

The kelvin is written without a degree sign because the temperature units are not degrees kelvin, they are called kelvins.

The symbol for kelvin is written as an uppercase letter (K).

Temperatures in kelvin can only be positive and so they require no sign. The temperature scale is named after the British mathematician and physicist William Thomson Kelvin.

In the science laboratory, temperature is most commonly measured using the Celsius scale, although it is not part of the SI. The size of a degree in Celsius is identical to the size a degree in Kelvin.

Conversion factors between temperatures in degrees Fahrenheit (°F), degrees Celsius (°C), and kelvins are:

temperature (°C) + 273.15 = temperature (K)

((temperature (°F) - 32) x 5/9) = temperature (°C)

((temperature (°F) - 32) x 5/9) + 273.15 = temperature (K)


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HCT-99 General 2.3.1

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Hand- held Luminous Color Meter
Gigahertz-Optik’s new and improved HCT-99-D is a compact and portable luminous color and illuminance meter.

One unique feature is the Delta- function which allows the measurement of the difference in color coordinates x,y or u´, v´ and color temperature as well. So deviations from reference light sources can be measured and displayed easily.

Due to its ease of use, the HCT-99-D may be employed in quality control and on the production line â€"œ but can deliver valuable data in R & D applications as well.

The ergonomically designed HCT-99 also features a wide dynamic range and fast signal display.
Gigahertz-Optik offers user-friendly OS-X1 software for the HCT-99-D as an option.

Calibration is provided by Gigahertz-Optik´s DIN EN ISO/IEC 17025 accredited optical radiation calibration laboratory and is traceable to international standards

Features:

Color coordinates x, y, u, v
Color temperature
Interface
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Windows based OS-X1 1 Software available
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For Light Measurement including:

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Illuminance
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Optionally Luminous intensity
Optionally Luminance


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http://www.advancedaquarist.com/2005/7/review/view



medium





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Last edited:
Julio... We can list the manufacturers spec sheet for any of a hundred different tri-color or spectrophotometer type sensors. I happen to own several myself...

However, we are concerend with the PAR that reaches our livestock, not measuring the "spectrum" of the bulbs.

Of course the spectral output of the bulb does directly relate to the PAR... but in a sense we do not need to see the spectral output.

The easiest (and most cost effective) way to measure your bulbs performance (with regard to the aquarium) is to measure the output of the bulb PAR (or PPFD) or PUR.

LUX, LUMENS, CANDLES, etc all measure light differently (weighted by spectral output) and are not that helpful for our purposes.

If I wanted to measure the bulbs TRUE spectral color as compared to the label that come on the box... then some of the units you listed would do a decent job. Ohterwise the apogee (or similar) quantum meter will suffice.
 
<a href=showthread.php?s=&postid=9928181#post9928181 target=_blank>Originally posted</a> by BeanAnimal
Julio... We can list the manufacturers spec sheet for any of a hundred different tri-color or spectrophotometer type sensors. I happen to own several myself...

However, we are concerend with the PAR that reaches our livestock, not measuring the "spectrum" of the bulbs.

Of course the spectral output of the bulb does directly relate to the PAR... but in a sense we do not need to see the spectral output.

The easiest (and most cost effective) way to measure your bulbs performance (with regard to the aquarium) is to measure the output of the bulb PAR (or PPFD) or PUR.

LUX, LUMENS, CANDLES, etc all measure light differently (weighted by spectral output) and are not that helpful for our purposes.

If I wanted to measure the bulbs TRUE spectral color as compared to the label that come on the box... then some of the units you listed would do a decent job. Ohterwise the apogee (or similar) quantum meter will suffice.
Click to expand...


Ok ......

http://www.licor.com/env/Products/Sensors/rad.jsp


My English is very bad for writing , but Look this review of Solaris, as they made it to make the measurement.


http://www.advancedaquarist.com/2006/8/review2


Methods.

"Photosynthetically active radiation (PAR) was measured with a LiCor LI-189 quantum meter with cosine-corrected submersible sensor. This instrument is within its recommended 2-year calibration period. Calibrations were made for ‘air’ or ‘water’ as appropriate. An Apogee quantum meter (using the ‘sunlight’ mode) was also used to take measurements within an aquarium, and these results were compared to those of the LiCor meter."




Greetings !!


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I have always like to measure Lux as it's a better measure than nothing, and not too far off, and the meters are far cheaper, more available.

Any way bulbs generate different colours by exciting different metal halide. As the bulbs are used these degenerate with time, so intensity drops. Different metals have different rates of decay, so the metals used to generate a 10K will have a different rate of decay to a 20K. Generally the bluer colours degenerate faster, so if you run your bulb for 6 months, as the blue bit has degenerated more than the red bit, so your bulb appears redder (as there's less blue than you started), and there is less intensity also.
Some of the rates in PAR lossage are quite high - I have heard/read people using 1000 watt 20K's swap them after about 3 months as about 20% of the intensity is lost after that time.
 
julio... no problem at all :) Yes the LiCor is a good unit for our purposes. It is somewhat expensive though.

Wayne, LUX is not really that close. There are instances when a very high lux bulb can have a very low par. I am not sure (never looked into it enough) but would imagine that loss of bulb output intensity and spectral degredation do not equate to a similar (linear relationship) decline in LUX and PAR. That may be something itneresting to graph, but I think it will vary wildly (the relationship between lux and par degredation curves) with bulb type and brand.
 
my pheonix bulbs are almost a year and a half old. I have 2 brand new bulbs sitting here for the past 5 months. I just dont know why I should put them in...

tank looks good, bright, no noticable increase in algea...color is still unquestionably "blue". I obviously cant say it hasnt changed, to me it hasnt... but when you see it every day, its hard to really notice the change since its so gradual. I wonder if when I put the new bulbs in eventually, if itll be a "OMG" kind of difference. but I doubt it will.
 
Bean - I tihnk Richard Harker has a crossplot of Lux against PAR and there is a pretty stable linear trend. I do not have the equation to hand (tho' it is in Delbeek and Sprung vol3).
Areze - only put one bulb in (assuming you have a 2 bulb fixture, and see if you can visually tell the difference, I think you might be surprised.
 
<a href=showthread.php?s=&postid=9940019#post9940019 target=_blank>Originally posted</a> by areze
my pheonix bulbs are almost a year and a half old. I have 2 brand new bulbs sitting here for the past 5 months. I just dont know why I should put them in...

tank looks good, bright, no noticable increase in algea...color is still unquestionably "blue". I obviously cant say it hasnt changed, to me it hasnt... but when you see it every day, its hard to really notice the change since its so gradual. I wonder if when I put the new bulbs in eventually, if itll be a "OMG" kind of difference. but I doubt it will.
Click to expand...
if its working i wouldnt touch it myself.
 
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