new setup possibilities ??

Color temp on specific lights from specific manufacturers will vary, but HPS and "warm" fluoros all are around 2700k, which is optimal red spectrum lighting for MJ flowering. MH and daylight fluoros are around 6500k, optimal blue spectrum for MJ vegging.

You can flower with ~2700k fluoros but will get significantly better results if you use HPS.

 

I got a 4k MH, and after realizing that, I've paniced a bit thinking its no good, but after asking in another thread, jcj said that it wont make a big difference if the MH is 4k or 6.5k, it has enough light in the right spectrum. I guess its no that big of difference if the light is 2.3k or 2.7k either

 

I have not flowered my plants under artificial light so I don't have first hand exp., but from what I've read the order of preference for flowering is HPS, MH and Fluorescent (CFL).

I'm thinking that the HPS is the best because most of its light is in the red/orange range of the visible spectrum, imitating the sunlight in the fall where there is more red because the sun is lower in the sky and has to penetrate more of the earth's atmosphere. MH works because it is just so damn strong even though most of the light produced is in the blue/violet range. (plants use light in the blue/violet and red/orange spectrum for photosynthesis.)

cfl's are not as intense but will work (from what I've read) if you have enough of them and in the red/orange range.

 

The color temperature does not really tell the story. It is the wavelengths in the 400-450 nanometer range (blue end) and around 675 nm on the red end that are used in photosynthesis.

I have seen a spectrum chart for a MH bulb that was listed as having a color temp of 4000 degrees Kelvin that showed a uniform output along the entire visible spectrum. THe green light won't be used, but it does produce light in the correct wavelengths so the bulb will be good to use (just wasting some of the light energy)

 

Hmm interesting.

Thing is, for some bulbs its hard enough to find their color temp (had to search company's site intensely) but to find a wavelength chart? where do you find the chart for your bulb?

 

I wish I knew. Some manufactures publish the light spectrum...most just list the color temp because that's what humans care about. The grow light mfg. are better at listing the spectrum. It takes a lot of searching...unless you have a spectrometer laying around.

I did find this comparison chart that lists color temp in relation to light spectrum. I'm not sure how accurate it is, but it's what I used when deciding on my mix of CFL mini-twist bulbs.

 

Wow thanks for the info.
Yea the guy at the electricity store had no idea what I was talking about when I tried to explain I need the same bulb with a different color, its not a grow store.

Anyhow, dont think venture shows such a chart for their lamps, so I will have to wait and see what happens I guess. Maybe I'm not reading the cholorphyll activity chart right, but it looks like 4k lamps are pretty much the worst !

 

I believe that the 4000K lamps are made for area lighting. They are almost perfectly balanced, producing a bright white light. They DO produce a lot of light in the blue and red bands, but there is a lot of wasted energy in the green and yellow range. They work because they're so damn intense.

In a CFL grow, you can be more efficient by using only lamps in the effective wavelengths, but since they aren't as intense, you have to be more spot on. I have learned that color temp (in degrees Kelvin) is only marginally useful. CFLs in the 5500 K range and also in the 2700K work for me.

 

Well then I guess my plants will be fine then. thanks!