Flouresent Light Color Temperature Accuracy

[Casperson]

Hey Guys,
Just bought a URI 10,000k 20w T12 bulb and it's got this redish color coming from it? In the past I've used Coral life brand and it's color index ran real whitish blue like a 10,000k should. Did my vendor send me the wrong bulb? Or is this what URI is putting out for their 10,000K? I'm using it for my refug. so I'm not sure it matters but, It seems to red to be a 10,000K. I purchased 2 and both of them are the same. Anyone with experience with URI? or other brands of 10,000k bulbs.

Thanks,

Tom C

 

[NaH2O]

Hmmm...that seems odd to me, as the only complaints I've read on 10000K bulbs (not necesarily that brand) is they look a little on the yellow side, but not as much as 6500K bulbs (usually by folks that like the more blue color of the 14-20000K). I personally like the color of a 10K, and find them to be white. However, I'm not familiar with that particular bulb, so here's a thread bump for ya. It might be the bulbs to burn in a bit, but also a call into the vendor just in case there was a mix up.

 

[liveforphysics]

First, let the bulb burn in. These fancy pants bulbs use at least 3 different phosphors, some of which have likely not found their post burn-in intensity yet.

Quoted from wikipedia:

"Because it is the standard against which other light sources are compared, the color temperature of a black-body radiator is equal to its surface temperature in kelvins, using the temperature scale named after the 19th-century British physicist William Thomson, 1st Baron Kelvin. (Note: it should not be construed that the color temperature refers to the thermal temperature of anything other than the black-body radiator.) An incandescent light is very close to being a black-body radiator. However, many other light sources, such as fluorescent lamps, do not emit radiation in the form of a black-body curve, and are assigned what is known as a correlated color temperature (CCT), which is the color temperature of a black body which most closely matches the lamp's light emission curve. Because such an approximation is not required for incandescent light, the CCT for an incandescent light is simply its unadjusted kelvin value derived from the comparison to a heated black-body radiator."


So, what thats saying, is that our excited phosphorus lamps we use dont actaully have a REAL color temperature. We have this correlated color temperature deal, and it really has quite a range of appearence it can take to our eyes while still indicateing the same fake CT (fake because they should all be labeled coralated color temp).

If our eyes didnt have this crazy curve boosting greens, yellows, reds and attenuateing blues, in theroy all the coralated color temp lamps would appear roughly the same. In practice though, they can all technically be 10k lamps, and yet appear pink, pure white, sky blue, violet, etc.

Think about the correlation being similar to finding an average grade. The class might have 5 A's and 5 F's, but the correlated average would be a "C". If somebody told you the class was "C" average, though technically correct, it sure can give a miss leading idea of the actual students grades (or perceived color temp in our case).

I hope this helps.

-Luke

 

[Casperson]

Thanks Nikki for your response,
I went right to the source and called URI (Ulraviolet Resources International). I spoke with a technical representitive who seemed to really know his stuff. He spoke about phosphors (Not sure of spelling here) and purity of phosphors and how their 10,000k flourescent can show a pinkish color. He basicly said that they utilize the best phosphors in their product from a German company (can't recall the company he said) He also spoke about how the real blue flouresent bulbs out there can be made to look like that by eliminating or adding certain amounts of phosphors to make it appear more white/ blue. Doesn't mean it's a better bulb at all. So that said, I guess it's about what is most successfull over your tank and what you like best.
He also said the reason the same Kelvin bulbs from different companies look different is partly because there is no Federal Standard for aquraium lighting, companies can make them any way they want.

By the way he said URI is working with Ushio ( who I know is a great company) to Distribute a MH bulb comming soon.

Tom C.

 

[Casperson]

Luke!
Sounds like you know your stuff!
The guy from URI was on target then.
His analogy was that of "Grade A Beef" And Angus" They both look the same but taste different." I think URI makes a good quality bulb even thought is doesn't appear to be the standard color (yet) for a 10,000K. Also haven't burned it for long at all yet. 30hrs.

Thanks,

Tom

 

[liveforphysics]

I noticed you said this bulb was for your fuge. Be very glad it has those other colors in it, becuase if you are useing a 10k bulb for growing cheato (or other macro algaes), you would likely be best off with something focusing on the green-yellow and red wave legnths. I found that my growth really came on strong when i switched from 6500k to 2700k bulbs over my fuge.

I'm not a biologist of any sort, but I dont belive that cheato can use those short wave legnths (<480Nm-ish) for much of anything.

Good to meet you, and I wish you the best with your tank.

-Luke