what is 6700k on light bulbs?

[aclockworkorange]

Good info. Someone should make a sticky thread with all this info.

 

[Pyramid_Party]

I used 8000K bulbs once, had a bluish color to it. I really did not like it though.

 

[FLESHY]

See...thats really strange. 8000k shouldnt be bluish at all. 10k is like pure white. It depends on who makes the bulb...and a lot of things. The system is pretty messed up.

 

[Zander_The_RBP]

See...thats really strange. 8000k shouldnt be bluish at all. 10k is like pure white. It depends on who makes the bulb...and a lot of things. The system is pretty messed up.

I agree


And most of the information given in this thread is either extremely simplistic or outright incorrect.


Colour temperature is a way of measuring the colour of a light source by comparing it to an ideal black body radiator. A black body radiator is a theoretical object that when heated to a specific temperature will glow a certain colour (same way an incandescent lamp gives of light and the reason the heating element in an oven glows red when it's hot) The hotter the object the bluer the light given off. Fluorescent lamps and Metal halides are not black body radiators so they are instead given a CCT (correlated colour temp.) Which is a very subjective comparison to a black body radiator at such a temperature. Because it is so subjective and there are no regulations demanding that such comparisons be accurate companies are allowed to say their lamps/bulbs are whatever temperature they see fit (often trying to use the most exotic sounding one as possible in order to make it sell better). Here is an excellent simulator showing what each temperature SHOULD be (if companies didn't outright lie about their lamps colour)

http://webphysics.davidson.edu/alumni/milee/java/bb_mjl.htm


Now because CCT is only used to compare the colour of the light sources pay no attention to the actual spectra given off by said temperature because it won't be anywhere near the same, and it's not supposed to be.

As you can see 5000-6500k are solid white any less and it starts to look yellowish any more and it starts to look bluish. Take a look at 10000k this was especially surprising to me (the first time i looked at it) considering that most lamps labelled as such look solid white and cheaper lamps will even look yellow, obviously this "Colour temp" system is broken.

Colour temp in relation to plants is a little more complex. Colour temp as you now know measures not the spectrum but the subjective colour of the lamp. Plants don't care about the "subjective colour" they care only about the spectrum given off by the light source.

Take a look at this link scroll downa bit and you will find a spectral chart for Anarcharis (a common aquatic plant) most plants follow this spectral chart very closely

http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookps.html

As you can see photosynthesis is more heavily weighted in the red and blue sections of the spectrum. This chart basically says that if you were to shine light of the peak wavelength the plant would be able to use more of that energy than if you were to shine a light producing a wavelength with a smaller peak.

Red and blue happen to be also how colour temp is measured so this makes it easy for us to figure out which temperatures will be best for our plants. Right?

Well sort of.
As i said before colour temp is by no means accurate when used for fluorescent lamps but it is generallytrue that higher temps will produce more blues and lower will produce more reds/oranges. It gets a little tricky when you look at colour temps between 4000-7000 these seem to have completely random spectra and often times one will be great for plant growth and another will be complete garbage. 1 myth is that colour temps lower than 5000 and higher than 10000 will be useless for plants when in fact the reverse is often (but not always) true. Colour temps in this range give off mostly green light (unless specifically designed for plant growth) so some will be the worst possible way of lighting your tank while others will have large red and blue peaks will a very small green one and be excellent full spectrum ways of lighting an aquarium. However going higher than 10000k will also grow plants just fine because there is less "wasted" output going to the green and yellow portions of the spectrum. And more productive output in the blue spectrum the opposite is also true. Lower colour temps (below 4000k) often grow plants very well because there is much less wasted output in the green and cyan (blue-green) and more productive energy in the red and orange.

The best way to light a tank would combine 2 bulbs at complete opposite ends of the spectrum (a 14000k and a 4000k one for example or a 20000k one and a 3000k one) or more descriptively one weighted very heavily at the red portion of the spectrum and one weighted more heavily at the blue end of the spectrum.

So what does actinic light fall into the picture? Actinic blue bulbs are bulbs giving off either 420nm light (violet) or 460 nm light (blue) these are absolute measures of colour, 460 nm light will always be blue for example) both of these wavelengths fall into the blue peak of photosynthesis and would be perfectly acceptable choices to light a tank if you like the bluer look (I personally do) just remember to supplement it with a "white" bulb too. These have a lot more productive energy per watt than a white or “full spectrum” bulb (Which are the same thing by the way fluorescent lamps by definition are full spectrum.)


Whew that was a long post hopefully enough people will read it and I won’t have to post it ever again.

 

[ucng]

I agree


And most of the information given in this thread is either extremely simplistic or outright incorrect.


Colour temperature is a way of measuring the colour of a light source by comparing it to an ideal black body radiator. A black body radiator is a theoretical object that when heated to a specific temperature will glow a certain colour (same way an incandescent lamp gives of light and the reason the heating element in an oven glows red when it's hot) The hotter the object the bluer the light given off. Fluorescent lamps and Metal halides are not black body radiators so they are instead given a CCT (correlated colour temp.) Which is a very subjective comparison to a black body radiator at such a temperature. Because it is so subjective and there are no regulations demanding that such comparisons be accurate companies are allowed to say their lamps/bulbs are whatever temperature they see fit (often trying to use the most exotic sounding one as possible in order to make it sell better). Here is an excellent simulator showing what each temperature SHOULD be (if companies didn't outright lie about their lamps colour)

http://webphysics.davidson.edu/alumni/milee/java/bb_mjl.htm


Now because CCT is only used to compare the colour of the light sources pay no attention to the actual spectra given off by said temperature because it won't be anywhere near the same, and it's not supposed to be.

As you can see 5000-6500k are solid white any less and it starts to look yellowish any more and it starts to look bluish. Take a look at 10000k this was especially surprising to me (the first time i looked at it) considering that most lamps labelled as such look solid white and cheaper lamps will even look yellow, obviously this "Colour temp" system is broken.

Colour temp in relation to plants is a little more complex. Colour temp as you now know measures not the spectrum but the subjective colour of the lamp. Plants don't care about the "subjective colour" they care only about the spectrum given off by the light source.

Take a look at this link scroll downa bit and you will find a spectral chart for Anarcharis (a common aquatic plant) most plants follow this spectral chart very closely

http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookps.html

As you can see photosynthesis is more heavily weighted in the red and blue sections of the spectrum. This chart basically says that if you were to shine light of the peak wavelength the plant would be able to use more of that energy than if you were to shine a light producing a wavelength with a smaller peak.

Red and blue happen to be also how colour temp is measured so this makes it easy for us to figure out which temperatures will be best for our plants. Right?

Well sort of.
As i said before colour temp is by no means accurate when used for fluorescent lamps but it is generallytrue that higher temps will produce more blues and lower will produce more reds/oranges. It gets a little tricky when you look at colour temps between 4000-7000 these seem to have completely random spectra and often times one will be great for plant growth and another will be complete garbage. 1 myth is that colour temps lower than 5000 and higher than 10000 will be useless for plants when in fact the reverse is often (but not always) true. Colour temps in this range give off mostly green light (unless specifically designed for plant growth) so some will be the worst possible way of lighting your tank while others will have large red and blue peaks will a very small green one and be excellent full spectrum ways of lighting an aquarium. However going higher than 10000k will also grow plants just fine because there is less "wasted" output going to the green and yellow portions of the spectrum. And more productive output in the blue spectrum the opposite is also true. Lower colour temps (below 4000k) often grow plants very well because there is much less wasted output in the green and cyan (blue-green) and more productive energy in the red and orange.

The best way to light a tank would combine 2 bulbs at complete opposite ends of the spectrum (a 14000k and a 4000k one for example or a 20000k one and a 3000k one) or more descriptively one weighted very heavily at the red portion of the spectrum and one weighted more heavily at the blue end of the spectrum.

So what does actinic light fall into the picture? Actinic blue bulbs are bulbs giving off either 420nm light (violet) or 460 nm light (blue) these are absolute measures of colour, 460 nm light will always be blue for example) both of these wavelengths fall into the blue peak of photosynthesis and would be perfectly acceptable choices to light a tank if you like the bluer look (I personally do) just remember to supplement it with a "white" bulb too. These have a lot more productive energy per watt than a white or “full spectrum” bulb (Which are the same thing by the way fluorescent lamps by definition are full spectrum.)


Whew that was a long post hopefully enough people will read it and I won’t have to post it ever again.

WOW That was impressive! Thank you very much for your huge post. I understand alot more about lighting now. very helpful to me and probably many others

 

[FLESHY]

RBP...I agree with you on many things. I wish I could explain as in depth as you can about the nuances of lighting science.

Im willing to bet that you will have to post that information again. Why dont you post it on one of our lighting stickies, or copy an paste it into a new thread so that it can get stickied?

 

[Zander_The_RBP]

RBP...I agree with you on many things. I wish I could explain as in depth as you can about the nuances of lighting science.

Im willing to bet that you will have to post that information again. Why dont you post it on one of our lighting stickies, or copy an paste it into a new thread so that it can get stickied?

Wow someone suggesting a post of mine be stickied ? Its an honor lol

ill go through that post maybe add some stuff and run a spell/grammar check and spruce it up before creating a thread specifically for it.

WOW That was impressive! Thank you very much for your huge post. I understand alot more about lighting now. very helpful to me and probably many others

No problem glad i could be of help Ucng.

 

[splant]

Wow RBP that was quite the informative post!

What combination do you use on your planted tanks? I looked at your page hoping for pics and ready to be impressed but sadly found none You have to put all that knowledge to use.

I still say actinic bulbs are of no use to a planted tank. They were designed to simulate light that penetrates deep water as in a reef. There has to be a reason why in my zillion hours reading about planted tanks I've never heard of anyone using them.

 

[Zander_The_RBP]

Wow RBP that was quite the informative post!

What combination do you use on your planted tanks? I looked at your page hoping for pics and ready to be impressed but sadly found none You have to put all that knowledge to use.

I still say actinic bulbs are of no use to a planted tank. They were designed to simulate light that penetrates deep water as in a reef. There has to be a reason why in my zillion hours reading about planted tanks I've never heard of anyone using them.

My tank is only partially planted actualy Mainly becuase it never was really intended to become planted when i set it up (150 gallon) but recently (past 6 months or so) i became intrested in planting it. The only problem was i had a bunch of convicts in there that would shread any plant i put in there (except the amazon swords which have thrived). And the light was never really strong enough but now that i have the funds to upgrade my lighting and my piranhas have eliminated all those pesky convicts hopefully i'll have a new scape and thread for it in the comming weeks.


Currently i only have 1 tank set up (thats my 150) and i run a 6700k and aqua glo combination but i am looking for a more blue and less purple combination so when i redo my lighting i will probably go with a 10000k and an actinic (460 nm) combo but im not sure yet. But there only t8 flourescents and my problem is they are hanging too high off the tank and i have no practical way of lowering them. I want to atleast get medium light/no co2 and get good at it before i consider making the jump to pressurized co2 and extreme lighting.


I may turn my 5 gallon quarentine tank into a planted one too i have the light, filter, heater, and everything it's just a matter of deciding on stock and plants.

I like to have a firm understanding of the science behind something before i actualy do it which is why i have spent far too much time researching lighting than actualy replanting my tank.



The main reason i don't think actinic bulbs are used in freshwater alot is because they are specificaly advertised for saltwater so no one really sees any point, but one of the best planted tanks i've ever seen was at my LFS and it used 50/50 6500k/420 nm bulbs and it had excellent growth and beautiful colours (both plant and fish).


I've got a ton of plants sitting in quarentine (with a 100 watt metal halide shining on top of them with only their roots in the water (which is loaded with fertilizer) and a very nice peice of driftwood to add to my tank so hopefully i'll be able to re-aqua scape very soon.

 

[jcardona1]

I still say actinic bulbs are of no use to a planted tank. They were designed to simulate light that penetrates deep water as in a reef. There has to be a reason why in my zillion hours reading about planted tanks I've never heard of anyone using them.

Exactly. The spectrum of actinic lights is only found in deeper water, like where corals grow. Deeper water contains a more blue spectrum because the red/yellow spectrum gets absorbed by the water first, while the blue continues into the depths.

Freshwater plants on the other hand grow in much shallower waters, therefore they have not adapted to use the blue spectrum of actinic lights. While actinics lights may still grow freshwater plants, I believe there's two reasons why you don't see people use them:

1. It's not typical of a plant's environment in nature. We try to re-create their natural environment, so we use lighting that matches what they get in the wild.

2. Actinics looks like ass on a freshwater tank, and look like even more terrible ass on a planted tank