I flowered with Sunmaster Warm Deluxe (3200K full spectrum)es for two years, no HPS. I didn't like the results I was getting - small buds, less weight, the plants seemed to stretch more than HPS for some reason, wouldn't finish, low potency. I switched back to HPS the first week of December, the SC got around 4 weeks of MH, the NB 3 weeks and the Skunkberry and Skunk around 2 weeks.

The UVB has a very blue light, it changes the grow room to white from HPS yellowish red. It's early yet but from the results I'm getting I don't think MH compares at all with UVB.

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I always liked about 3:1 HPS:MH.. I preferred the buds closer to the MH actually, but they were smaller/less dense..

it's all in the Kelvin of the light

The reptile sun UVB lights are 10,000 Kelvin
If your going to use MH light just make sure your
bulb has a high enough Kelvin.
If you don't your just wasting your time, and money.

ie Link:http://store.atotlamps.net/servlet/-...-kelvin/Detail

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The actual physics of HID and the definition of the Kelvin color actually make that statement kind of sketchy.. 10000K does not mean your peak output wavelength is 290nm, that wouldn't make for a very bright light at all..
But in practice its the best bet since its pretty tough to find output spectrums that range below 400nm or so..

You are correct. Kelvin measurements only are applicable from 1000K to 10,000K based on the color a perfect black body radiator appears at that temperature. This ranges from the reddish orange of candlelight to the dark blue of the sky. Since our bulbs are not perfect black body radiators, their color temperature is always an approximation anyway. Also, since color is a human perception it only applies to the visual spectrum so ultraviolet light cannot have a kelvin rating since it's invisible to our senses.

Our bulbs aren't even close to blackbody radiators! Except perhaps from the heat glow.. Gas discharge light has nothing to do with heat, photons at specific various frequencies are emmitted when electrons make transitions as they pass through the gas mixture..
Heat is a byproduct, and its needed to reduce the breakdown voltage, but like a blow torch, the light from HID lights is not Kelvin black-body related at all.. They don't even try to match a BB curve on the spectrum..

I did say that our bulbs are not black body radiators but you are incorrect that they don't try to match the color. What it really means is that if we were to compare the lamp's color to a black body at 6500K, it would appear the same to a human observer. The technically correct term for this is Correlated Color Temperature (CCT) which is defined as the value of the temperature of the black body radiator when the radiator color matches that of the light source. CCT implies a color match to a black body at the specified temperature.
Depending on where the spectrum of the bulb falls along the color chromicity scale the bulb manufacturer will label it with a kelvin color depending on where it falls closest to the black body line you see in that diagram. If you notice, after about 10,000K the line stops at infinity meaning any CCTs over 10,000K are pretty meaningless.

Just like lumens, CCT labels are meaningful only to people and plants only care about whehter they receive the spectrum they require to affect photosynthesis.

I hope we start seeing a trend toward bulb companies measuring and optimizing for PAR or photosynthetically active radiation rather than focusing on a meaningless number (at least for our purposes) like CCT.

That actually is the theory behind LEDs, is that they can deliver the same PAR without wasting energy on unusuable wavelengths. I think the only problem with LEDs right now is finding the right combination and I bet it will require 4 seperate wavelengths not the 2 that are currently being marketed.

Interesting, I just found this link for GE's Lucolux high PAR lamp. It seems they market this to commercial growers. http://www.gelighting.com/eu/resourc...rticulture.pdf

I realize you get the gist of the physics, I just wanted to stress the fact because its vastly misunderstood..
What I was referring to is the difference between the 'apparent' color (Kelvin rating) and the component wavelengths that go into making that apparent color.. The actual spectrum doesn't match a black-body curve of any type at all, and they don't attempt to make it match.. With plant lights they focus the energy to logical transitions for absorbtive wavelengths, and for human lighting they focus on the functional result for our eyes.. I've never seen a single HID spectrum that even eludes to a black-body curve though even when integrated over a large d_lamda like they show on the boxes.. Plant spectrums look almost like the opposite curvature to a BB and human lighting usually has peaks ranged across the visual spectrum..

I agree it is widely misunderstood but there is some correlation to the talk of needing more 'blue' light (6500K) for vegging vs. the reddish HPS (3300K) and I think that confuses people unless they understand the spectral energy output curves and such. You and I are probably fortunate to be science oriented in this hobby because it can get quite technical in a lot of different areas.

subscribed - IM CONVINCED THIS IS A MISSING KEY!

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