Possible SCAM/HEALTH alert: lighting

[BigDaddy]

Okay, since I was partly responsible for jacking the thread, I'll bring it back on topic

I think Mr. Trevor-Jones sums it up quite nicely here:

"Fluorescent and gas discharge (e.g. Metal Halide) lamps do not follow the theoretical black body and the rated colour temperature is only an approximation of the colour of the light produced. This is largely because these lamps produce an interrupted spectrum with peaks in some wavelengths while some wavelengths are not radiated at all. However, lamp manufacturers will still publish colour temperature information for their lamps which would be more accurately termed "apparent colour temperature".

In other words, its a comparable in order to accommodate the lowest common denominator - the consumer.  

[beowulf]

I am far from an expert so please enlighten me, the lights are coated differently to either better bring out the color of fish or help pants grow etc?

[BigDaddy]

Simple answer - yes.

[PaleoFishGirl]

k guys back on topic?

[mseguin]

So then why does the bulb advertise a 10000K or 18000K? Is that the highest peak?

[beowulf]

k guys back on topic?

Hence my lightning question to try and bring it back lol.

Now how does the coating effect the UV output?  I know for the UV filter that I got from Colin the bulb has no coating which I guess is to allow the UV to kill all the bad stuff.

[beowulf]

So then why does the bulb advertise a 10000K or 18000K? Is that the highest peak?

And how long does this last?  I mean if it is recommended to change bulbs every year....

[Shouganai]

I know with the UV tubes I need to buy for my reptiles, the advertised UVB output is something like 10x higher than what it actually is when read with a UV meter, and the bulbs are pretty much useless for UVB output after 4-6 months of regular use (10-12 hours/day).  When I was keeping fish I'd replace my NO tubes every 6 months.  I had my CF tube for over a year though, I wasn't sure when/if I should have replaced that, as I didn't really notice a drop in brightness like with the NO tubes.

The companies (for the reptile bulbs at least) get by making these claims because they are based on the peaks of the tube's output, however short and fleeting that may be.  I can imagine, considering some of these bulbs are made by the same companies that produce lighting for aquaria, that they pull off a similar 'scam' for those consumers.

[Saltcreep]

(And well they should; IMHO Diatom Filters aren't worth the health risk )

Interesting. Diatomaceous earth used to be used to filter the fry shortening or oil every night when I worked in the fast-food industry. Maybe they still do.

[dan2x38]

if I am following along here with BigDaddy the tubes are rated on peek output light temps. not the average output... so their claim is in fact true just deceiving... similar to the rating of audio speaker output wattage is peak power?

[homestar726]

I always found that funny too. Aquarium light users are being lied to all the time about their lights. You wont have ever find a true 10,000k or 12,000k. its impossible like dpatte mentioned. Below is a light chart to prove this.

[BigDaddy]

The charts you are showing are for incadenscent light "black body" temperature ratings.  As was previously mentioned, fluorescents can not be measured using the Kelvin scales for black bodies, as it does not apply to how they emit light.

[dpatte]

So, in effect, the kelvin temperature rating of a flourescent light should be ignored as it doesnt indicate actual visual colour, or black body colour.

As mentioned in wikipedia, a spectrum chart is more relevent, and only if its graduated in 2 nm increments.

This should be matched against plants (or sealife) requirements - which i presume, for a freshwater tank, would be close to noon daylight = 5600K blackbody

[dan2x38]

but is kelvin not a measure of engery?

[BigDaddy]

Kelvin is a measurement of temperature, or more specifically, absolute temperature.  The reason light has a measurement in Kevlin is based on the temperature a black body would have to be at to emit that specific color range of light

[dan2x38]

so all said and done what does this translate to regarding our aquaria lights? scam or no?

[dpatte]

I have the cases for a '6500K' corallife CF bulb, and a '10000K' corallife CF bulb

Want to hear something interesting.

Both cases have identical spectrum graphs!

so tell me how the light output from these bulbs is different - please.

[BigDaddy]

It isn't a question of output, it is a question of "apparent colour" as viewed by a human.  Having both a 6500K bulb, and a 9325K bulb, I can easily see that the 9325 K bulb has more of a blue/purple tint to it, whereas the 6500K is clearly mostly white with hints of yellow

[dan2x38]

would common T12 lighting store high output blubs be just as good?

[dpatte]

It isn't a question of output, it is a question of "apparent colour" as viewed by a human.  Having both a 6500K bulb, and a 9325K bulb, I can easily see that the 9325 K bulb has more of a blue/purple tint to it, whereas the 6500K is clearly mostly white with hints of yellow

But there is something definately amiss if the packaging of two different bulbs purport to produce the same colour spectrum, yet they appear as different colours to the naked eye. That makes no sense at all.