PC lamp spectrums

[Mr. Fosi]

So I sent out a request for old PC lamps some time ago so I could compare them and see if spectra really do shift over time.

 

Why would you want to know this? Because "spectral shift" is often blamed for algae and other problems.

 

Here is the setup I used.

 

 

 

 

 

 

Here is the data.

 

Three Odyssea "Actinic Blue" lamps of different ages (note the different intensities). See that the spectral peaks match perfectly, regardless of age.

 

 

 

 

Three Tru "Actinic 03" lamps. The green line is the output of a brand new lamp scaled down to fit in the same range as the older lamps. The spectral peaks are identical regardless of age.

 

 

 

 

Three Tru daylight lamps, 2x10000K and 1x6700K. The green line is a brand new lamp, scaled to fit in the same range. The peaks match regardless of age.

 

Look at the 6700K, it is an old lamp (8-14 months of 8 hr days) has the same peaks as the 1000K lamps but they are higher than the 10000K in select ranges even after all that time.

 

 

 

 

Here are some comparisons between the Odyssea and Tru brands. You can see that the actinics are very different (the Odyssea lamps put out a lot more UV) which accounts for why the coloration is so crappy under the Odyssea actinics. Also note that the 12000K spectrum looks remarkably like the 10000K spectrum but it is much brighter even though it is older than the Tru lamps and ready to burn out (it was tough to get it to fire).

 

 

 

 

 

And finally, here are the PAR comparisons I have been able to make.

 

 

- Tru 10000K lamps lost 44% of their PAR within 12 months.

- Tru Actinic 03 lamps lost 65% of their PAR within 12 months.

 

So then, you should change your lamps before they are a year old but not because of spectral shift, because of the loss of intensity.

[evilc66]

Some very interesting results there Fosi. The drop in PAR was probably the most surprising. I wouldn't have expected such a heavy drop.

 

You could be the next Sanjay Joshi for PC and T5 bulbs

[Mr. Fosi]

Well, I firmly believe that MH is the best bang for the buck with regard to PAR intensity and color and so I am glad that someone like Sanjay has tackled it. I don't know what his setup is, but I suspect that it is more quantitative than mine is. My spec isn't even calibrated for absolute irradience, which is why I have it mounted on that tripod; I wanted at least a little control of reproducibility.

 

Even though MH is the bomb and I, personally, will probably never do back to fluorescents, I think that comparisons of PC (and T5!) lamps are badly needed. As you can see, there are some inaccurate claims about them floating around and it seems as though if we can cross "spectrum shift" off as a cause of algae problems in some tanks we can get to what the real causes are.

 

I still would very much like to see 10000K & actinic lamps from other manufacturers. I have some old JBJ 24W lamps that I got from polyppeaty and 121a but I don't have the ballast to run them. I thought I could run them with a one of my magnetic ballasts but apparently they are designed to fire lamps that have starters in them and I don't think the 24W lamps fit that bill.

 

I'll keep looking for a way to fire those 24W lamps and as soon as I do, I will graph and summarize the results here.

[Waterproof]

Great test! Thanks! This info is really good for people w/ budget softie systems or picos. The ability to run bulbs for up to 12mo, rather than 9, w/o fear of spectral shift is nice.

 

How about if we give you a Cree LED and let you run a 4-7 yr test on intensity decline?

[Mr. Fosi]

I'd better be gone from here and away from this spectrometer in 4 to 7 years or I'll shoot myself!

[The Nomad]

Thanks for the link Mr. Fosi!

[121a]

never seen the results, really good to know though. hey those oddysea bulb aren't half bad LOL.

[Mr. Fosi]

Glad you found this. Now if I can get a ballast that will fire the lamps you sent, there will be some updates and additional data.

 

About the Odyssea lamp quality... It depends on what you consider "good". The PAR and longevity are fairly good but the color is total crap.

[Whacked]

Great info!

[SPS20]

One possible hypothesis to explain algae blooms under older lamps: (Apart from water quality)

 

Perhaps some species of nuisance algae are photoinhibited under new bulbs, or just outcompeted by other species of algae that have higher PAR requirements. As output tapers off, photoinhibition could cease, or other species of algae that were formerly accupying surface area died off from loss of intensity, and were replaced by nuicance species.

 

This isn't a hypothesis I thing is neccessarily true or likely, but rather a possible explanation for what some have stated is a pattern they have noticed.

[Mr. Fosi]

Well, one thing is for sure: cyanobacterial phycobillin complexes are more adventageious under low-light situations and I would call PC-lit tanks "low light".

 

One other thing that I was thinking but haven't had the time to quantify is that the output peaks seem to shift in ratio to one another. They don't go away or miraculously appear, but that perhaps some colors decrease while others remain relatively stable.

 

If you look back at those graphs, you'll see that some of the peaks are approximately the same height regardless of lamp age but other areas of the output decrease. I would like to quantify this apparent change and run some stats on the numbers to see if there is a significant difference... The problem is I don't know how to do that quantification in a meaningful way.