Confused about Kelvin ....

So I read in a good book that to grow short and stout clones and seedlings, I would want 4100k bulbs. They are for the Florescent light fixture I want to get.

But the company only sells 3000k or 6400k bulbs. Am I missing something?

I would be using the light for clones and seeds only. Whats the best kelvin rating to use?

It sounds to me like you don't have a lot to choose from - but maybe that's ok! 3,000 K is very close to 2,700 K, which is the best spectrum for vegging lights. And 6,400 K is even closer to 6,500 K, which is the best spectrum for flowering lights.

So here's what you could do: use one tube @ 3,000 K and one tube @ 6,400 K, that should average out to be 4,700 K (close enough!).

T.H.Cammo said:

It sounds to me like you don't have a lot to choose from - but maybe that's ok! 3,000 K is very close to 2,700 K, which is the best spectrum for vegging lights. And 6,400 K is even closer to 6,500 K, which is the best spectrum for flowering lights.

So here's what you could do: use one tube @ 3,000 K and one tube @ 6,400 K, that should average out to be 4,700 K (close enough!).

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I'd afraid you have it the wrong way around friend. The 3000k is for flowering and the 6400k is for vegetative growth. If you want something for clones then go for the latter. You cannot add them together and end up with light with a colour rating in the middle. But by having one of each, you'll have two peaks of light which roughly correspond to chlorophyl a and b. My advice is either go for all 6400k or mixing them up a little.

Well you can never go wrong with Leds can you?

Are you sure about that curious soul? I have a top rated growing book that says your wrong. It says 6400k for flowering and 4100k is best for vegg.

Anybody else know the answer to this?

I'm sorry, but it's 6500k for veg, 2700 for flower.The 2700 is closer to the red spectrum,which is what the plant starts to get more of outdoors as the season turns to fall.The 6500 k is blue spectrum, which simulates the more direct light of the summer season, when it does most of its vegetative growth.
https://www.rollitup.org/view.php?pg=faq&cmd=article&id=587
https://www.gardenscure.com/420/lighting/66308-help-warm-white-cool-white-flouros.html (scroll down to cecil b.'s answer here)
http://boards.cannabis.com/indoor-lighting/151557-light-spectrum-can-anyone-help.html
(several posts here)

T.H.Cammo said:

It sounds to me like you don't have a lot to choose from - but maybe that's ok! 3,000 K is very close to 2,700 K, which is the best spectrum for vegging lights. And 6,400 K is even closer to 6,500 K, which is the best spectrum for flowering lights.

So here's what you could do: use one tube @ 3,000 K and one tube @ 6,400 K, that should average out to be 4,700 K (close enough!).

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Why are most of the hps bulbs I find 6400k kelvin.
I just read off of this site faq that hps lights are best for flowering. Then wouldnt the hps lights come with 2700k?

I can't personally answer that one, good question...but if you turn on a hps light, you are definitely going to see that it is a warm orange, like autumn sunlight, and the metal halide is a blue white, like spring and summer.

mario60185 said:

Why are most of the hps bulbs I find 6400k kelvin.
I just read off of this site faq that hps lights are best for flowering. Then wouldnt the hps lights come with 2700k?

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Lemme go get my lights and I'll look at the package.

Thanks for the replies so far. I guess I should smoke after I do research from now on.

Ok...my one Hps says nothing.The other one says 20000k, and that's not a typo.My MH conversion bulb says 6000 k though. And I have a third hps here, which says nothing about the spectrum either.And every bulb is shaped different.One has all the writing in either Chinese or Japanese.

Damn this. I believe I am wrong. I will do as you said. Im glad I figured this out now, im buying lights tomorrow.

Hey, we all have to learn..I was confused about the lights at first too.Just remember, blue before red, cool before warm...that way you get the order straight.Now I should probably start a thread to see which of these three different hps bulbs is better for flower,if there's a difference.....

mario60185 said:

Damn this. I believe I am wrong. I will do as you said. Im glad I figured this out now, im buying lights tomorrow.

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mario60185 said:

Are you sure about that curious soul? I have a top rated growing book that says your wrong. It says 6400k for flowering and 4100k is best for vegg.

Anybody else know the answer to this?

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No - CuriousSoul is correct! I said it back-ass-wards. My bad!

But I'm not so sure about the "two peaks" theory because flourescent light is such a broad bandwidth that there are still plenty of other wavelengths to average out. The Kelvin temperature rating is only indicative of the predominant spectra not the entire spectrum. I could be wrong, but there are lots of people using mixed spectum lighting for this exact reason. Let me consult my sources!

I think if theres light it will grow, but I also like to get things right the first time, so I do alot of research. Butt im always baked too.