The 2700k is for flowering, the 6400 k is for vegging. Or at least that is what I’m doing. Good luck. I’m sure someone will correct me if I’m wrong.
Tom
Thanks Latewood found on ebay and amazon 59.99 free shipping
Thanks Tom u think can get buy just using one with highest lumens
Latewood is correct and brings up a good point. And a good light will usually include the info of how many lumens at a specific distance from the light and how many square feet or meters it should be able to effectively cover. They will also often give two distances with a further distance equaling a larger coverage area but recommended for veg at the further distance. Because of the inverse square law of radiation, the intensity/lumens of the light will greatly reduce, exponentially, the further you get from the light.
Think I’m gonna with that one company reviews are pretty good for every damaged bulb they ship new out which is kinda of a lost for them considering cost of bulb by itself
Your pics is that using the cfl’s your talking about they look good hoping got that turn out
yes my girls 2015 cfls
Hell!!! I might buy one 
Yes you can get by useing just one kind, but there is a different light spectrum in the 2.
Tom
White light is vaguely made out equal amounts of 3 colors that our eyes can see, reb, blue and green. Lumens is a measurement of brightness to how our eyes see the electromagnetic spectrum, i.e. radiated energy, and our eyes see brightness mostly from the near green spectrum segment of light, which is almost useless to plants. So those lumen numbers may not represent the intensity of the PAR, or photosynthetic active radiation, available to the plant’s leaves.
As others have said, you can use one light the whole grow. 5000K-6000K is generally considered true white light, and sunlight is usually pretty much about 5500-6000 all year long, even in the winter. Below these numbers the light becomes more yellow, orange or redish. And above this number the light becomes more blue.
However plants need much more red light than they do blue light, only about 20-30% of the light need to be blue to keep your plants happy and healthy.
It is generally understood that plants use mainly/only the blue and red parts of light and that more blue light, and blocking a specific hue or shade of red, not all red, just a small section of the red spectra, prevents unwanted excessive stretching between internodes. And that red light is more important for flowering/fruiting. And so blue-er lights are used for veg and redder lights are used for flowering. Also vegging takes place outdoors during the spring/summer when the sun is more directly over your area and fall winter is when the earth is tilting away from the sun causing it to pass though more atmosphere not unlike closer to sunset, and this is when cannabis flowers out doors. One can easily see why these color changes might be used to replicate some changes in sunlight that occur through the different phases of growth.
Plants grown in all red light will grow to be overly tall and leggy and ones grown under all blue light may be low-growing and stocky. Overall, more red light is needed than the blue in photosynthesis regardless of vegetative growth or flowering/fruiting.
You can look into the exact specs about the lights from the manufacturer and determine eventually if you want to buy each light, but to start, I’m sure the 6400K will do well for you for all phases of growth.
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Thanks a lot that helps a lot in my decision working on temp control now looking into decent exhaust fan 6" good price
Good thread; Great info. 
how far away from the plant does 300w leds need to be?
Any reason why you would use a T5 over CFL bulbs?
Was thinking of using 2x 120w CFL for VEG and a 400w HPS for flowering in a 3x2 space. Using 400w MH for veg at the moment but it seems to be overkill in the first 2 weeks and switching would save me electricity…but think the plants would grow slower?
High output T5s put out more intensity/lumens per watt and the prices are such that you wouldn’t save any money by buying high enough wattage CFLs or enough regular wattage CFLs per square foot or square meter. Ideally you want about 40-50 watts per square foot, or about 400 to as much as 600 watts per square meter.
Another thought is you could get an adjustable ballast for your 400 watt HID lights, and you could drop the wattage your 400 watt MH is actually using during veg.
Also, some other info that might help when comparing stats and prices of T5s vs. CFLs or thinking about dropping the power on a HID:
Seedlings and clones require about 400-1000 lumens per square foot.
Vegetative growth requires about a minimum of 2,000 to 3,000 lumens per square foot.
Flowering requires about 5,000 to 10,000 lumens per square foot, ideally, and can take possibly much more – which you easily have covered with you 400 watt HID light in your size area.
10,000 lumens is about the average power of the sun at sea level on a clear day at high noon. 8,000 - 12,000 lumens is supposed to be about the average power of the full sun without any overcast or no clouds depending on altitude and potentially other factors.
It’s not ideal, but you can make do with 2,000 lumens for an entire grow if necessary.
And don’t forget, lumen ratings are at a specific distance and will increase or decrease dramatically depending on distance from the leaves/canopy due to the inverse square law of radiated energy, i.e. light and the rest of the electromagnetic spectrum.
It depends on the type of LED system, usually there will be recommendations from the manufacturer.
It greatly will depend on the type of LEDs, the power of the individual LED diodes and the type of lensing they have. If the lens on the LED does not put a very wide angle on the LED and the colors of LEDs are not the most evenly distributed, then you probably wouldn’t want it very close to make sure the leaves are all getting even amounts of all colors or spectra.
LED’s in general tend not to get very hot with heat and with many the leaf could be nearly touching the LEDs, but some LEDs with very high power diodes can still cause bleaching of the leafs or buds of they get too close to the lights, this can deteriorate and prevent proper THC production as well as bleaching out the chlorophyll.
As a general rule of thumb, most LEDs are designed to work best at about 18 inches from the canopy/leaves. Some are safe as close as 6 inches or maybe even quite a bit closer, but most will be most effective at about 12-18 inches.
Happy growing,
MacG
thanks! 1st time grower need all the support I can get
I like T5 over CFL because of the light systems profile. T5 give you more headroom, and disperses the light better over all than CFL; IMO