Best color temp for veg?

Excellent, sorry I missed that. Can you provide a link?

Rahz said:

Excellent, sorry I missed that. Can you provide a link?

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Sure, man. I'm still looking for the link. Here are the pictures from the research paper I found, so the link can't be to far back from there.

Oh wait, here it is. @heckler73 posted it.
In the meantime, as I mull over the details, have a gander at this little gem I stumbled across:

http://leds.hrt.msu.edu/assets/Meeting/Optimal-spectrum.pdf

As those pictures demonstrate, a high ratio of red light does cause stem elongation (even occurs to individual cells). Well documented and known effect. Doesn't prove much.

Excellent, thank you. I'll read it this evening.

Those studies were originally posted by chazbolin, from a conference he attended recently

https://www.rollitup.org/t/the-future-of-led-u-of-a-ceac-2015-led-symposium.861724/

Doer said:

Sure, man I'm still looking for the link. Here are the pictures from the research paper I found, so the link can't be to far back from there.

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that looks like a lot of stretch under the reder light. the neutral light looks the best with about the same sized leaf as warm white, but tighter node spacing just a bit more than the cool white.

4000k ftw

Positivity said:

Those studies were originally posted by chazbolin, from a conference he attended recently

https://www.rollitup.org/t/the-future-of-led-u-of-a-ceac-2015-led-symposium.861724/

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Well, that not where I got it, heck posted it in the Tech section. But, thanks for the link.

http://www.sciencedirect.com/science/article/pii/0002157176900455 is a pretty good read if you have access.

bicit said:

that looks like a lot of stretch under the reder light. the neutral light looks the best with about the same sized leaf as warm white, but tighter node spacing just a bit more than the cool white.

4000k ftw

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I think there is mix up. I see it all the time. Stretch is not what we are seeing. That is growth rate. That is booming to be large.

This is stretch.

Rahz said:

Would be interesting if there was a documented side by side veg only grow, 3000, 4000, and 5000K.

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I like 6500 t5 tubes,I'm vegging with 96 watts in a 2x2.5 tent if your interested in any data.

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bicit said:

that looks like a lot of stretch under the reder light. the neutral light looks the best with about the same sized leaf as warm white, but tighter node spacing just a bit more than the cool white.

4000k ftw

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Read the paper that was posted. Don't just look at the pictures.

Snapper said:

As those pictures demonstrate, a high ratio of red light does cause stem elongation (even occurs to individual cells). Well documented and known effect. Doesn't prove much.

Click to expand...

Read the paper.

bicit said:

Keep in mind most people veg under metal halide, which are typically ~4000k. So could be something there... or not

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I have 2 solar flares I can take some high resolution shots if you know what the diodes look like from the projecting face?

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Doer said:

Read the paper that was posted. Don't just look at the pictures.

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No time, drive by post with the telephone

Ain't got no time to READ... I don't even know how to be honest...

I have my hands on some CXA 3590 6500k's just 4 of them the BD bin

KNNA recommended 25-30% blue for vegging and 15-20% blue for flowering (PAR Watts). Yes it is possible that his reasoning is incorrect, incomplete or outdated, but he was no fool so his recommendation still has weight to me. I run CXA 5000K which is about 24% blue by power according to Mr Flux, maybe higher according to SDS or Alesh.

I ran seedlings under 3000K and they stretched quite badly. I tried them under 5000K and they were stocky, although it was not a perfect test because the 5000K intensity was higher.

I have tried vegging with warm white/blue/red/deep red with 25% blue and that worked well, but color mixing and lensing/reflecting was a problem. I tried 4200K at a good level of intensity and internode length was still too large with sativa dom hybrids and hybrids in general. Now I run straight 5000K COBs. Easy to lens/reflect the light and no color mixing problems. Internode length is AOK. Efficiency and price is incredible.

Yeah if I were to build a pure vegetation fixture, it would either be all 5000K or a 2:1 ratio of 5000K and 4000K. The 5600K is enticing though...

I've thought about this topic before in my free time and would never recommend vegging with anything lower than 4000K (given the choice of course).

Don't ask me why but it just makes sense after my time here absorbing the free-flowing knowledge.

5000k works great for me, i'll be sticking with that. Perfect node spacing for my tastes. Even with a few reds in the mix, no problem

6500k hands down!