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Cfl light 6500K or 2500K?

Discussion in 'Newbie Central' started by bastard92, Feb 7, 2010.


    bastard92 Member

    I made the mistake (?) to buy ufo 120w led, I was disappointed ...
    Now to fix it, I plan to add more lamps

    The lamp arrived from Hong Kong has led orange and red, a few blue

    Blue LEDs are very important ...
    I would not take a blue LED panel, for reasons of space

    Then I would use the CFL ...

    The question is:
    To correct the blue LED, I have to take the 6500K or 2500K (red)?

    PLs reply

    RichiRich Active Member

    Listen mate, I'll lay it down simply for you.

    There are 3 kinds of lights that you should use for growing - anything else is not very ideal and will not guarantee a good yield.

    They are Fluorescent lights, reffered to as CFLs ; Metal Halide Lamps (MHLs) and High Powered Sodium lamps (HPS).

    These kind of lamps have different specifications.

    Now the fluorescent lamps (CFLs) are practical because they don't use so much electricity and don't emit much heat, meaning your plant(s) can grow very close to the bulb, and even touch it, without any problem. They can be used throughout the whole grow, but don't expect miracles.

    Metal Halide Lamps (MHLs), they get very hot. They're good mostly for the flowering stage and tend to use up a lot more energy than fluorescents.

    As for High Powered Sodium lamps (HPS) - most growers use this kind of lamp because of it's greatness. Like any kind of lamp, they come in different amount of watts - the more watts you have, the more light, the better for your plants. I'm using a 250 watt with great results, however these can go up to over a 1000 watts.

    HPS lamps are great for all stages of plant growth - that's why so many people use them. Keep in mind they can get quite hot, just like the Metal Halide Lamps, so be careful how close your plants are.

    Hope that clears things up for you. I highly recommend you look at this guide for lighting : http://www.rollitup.org/general-marijuana-growing/723-things-know-about-lighting.html

    Remember, not many people on this forum will be as helpful... You should really look by yourself and try and learn individually. It pays off.

    Peace and happy farming,


    weedyweedy Active Member

    The K stands for Kelvin and it is a measure of color temperature. Basically, 6500 is warmer and mostly found in Metal Halide lamps while the 2500K is cooler which is mostly in HPS lamps. So that really depends on the stage of your grow. If you're vegging, 6500 is ok. If you're flowering, 2500 is better. I suggest you get the 2500.

    weedyweedy Active Member

    Metal Halide lamps are not good for flowering because they will only give you fluffy buds.

    If you have to chose one type of bulb for your grow, go with the HPS since the end goal is to get good buds.

    bastard92 Member

    Then the blue LED(430nm) would be 2700K CFL(flowering)?

    CdnBud Well-Known Member


    MrBlanco Active Member

    6500k is blue light which is better for veg.
    2700k is red light which is better for flower.

    You can use either for your entire grow. I only use 2700k cfls because in my area they're half the price of the 6500k and if I wanted to spend $100 on cfls I would've just bought an hps to begin with. I haven't seen the stretching issue people say will happen if you veg with 2700k cfls.

    ravenraybill Member

    There seems to be a lot of misconceptions about CFLs out there.

    There are basically two general spectrum of light that you need to consider.

    The first, generally referred to as 'blue light' is used in the vegetative state of plant growth. This type of light promotes growth of the roots, stems and leaves. A lamp can truly be said to be in the blue spectrum if it has a color temperature of >6000K. CFLs are readily available in this range (1), although they tend to be somewhat expensive.

    There seems to be the general opinion here that if you have to pick between 'blue' light and 'red' light, then you should go with 'red' light, because it promotes bud density - which is true - but one must also keep in mind that buds cannot properly be produced at all without an adequate root system, healthy leaves, and stems capable of efficiently allocating nutrients throughout the plant. Therefore, adequate levels of 'blue' light are just as important to the plant as 'red' light (particularly in the early vegetative stage of growth).

    On a side note, metal halide lamps tend to be in the 'warm' to 'cool' white range - which is about 3500 - 5000K. Although they are available in the >6000K range (2), these tend to be extremely expensive 'special application' (aka grow light) bulbs. 'Cool' white metal halide lamps may be used - to great results - in the vegetative stage of growth, but the light that they produce isn't quite as useful to the plant as higher color temperature (>6000K) lamps, such as fluorescent, CFL, or specialty metal halide. The main advantages to metal halide lamps is their intensity and efficiency. Despite popular perception, metal halide lamps are actually quite a bit more energy efficient than fluorescent or CFL lamps - metal halides get around 80 - 90 lumens / watt of energy used, while CFLs get around 60 - 75 lumens / watt (3) (4). Beyond that, light from metal halide lamps travels farther distances and has more penetrative power - transferring more light to lower leaves.

    The second type of light is 'red' light, which as already noted, promotes bud growth and density. A lamp can truly be said to be in the 'red' spectrum if it has a color temperature of <2200K - although for the purposes of plant growth, it is not necessary to have light lower than 2200K. The lowest commonly available color temperature for CFLs is 2700K (5) - which isn't really in the 'red' spectrum at all. Therefore, CFLs are not ideal for the flowering stage of growth - although they can be used. High pressure sodium lamps, which typically have a color temperature from 2000 - 2200K, are much more effective in the flowering stage.

    Well, that's about all I have to say, except for a couple minor notes:

    High pressure sodium lamps are by far the best, having a high light output intensity, an ideal color temperature for their particular application, and the best energy efficiency (>100 L/W). In this respect, specialty metal halide (with a color temperature of >6500K) are also highly effective for their respective application, although in many cases they are considerably overkill - sometimes to the point of literally killing young plants or clones by either heat or light intensity.

    Color temperature, although useful as a general guideline, is not an entirely accurate way of measuring a lamp's usefulness to plant growth. In order to get the best idea of a lamps usefulness in any given stage of growth, the color temperature must be considered in combination with a lamp's PAR rating - which is a measure of the photosynthetically active radiation that the lamp produces. Unlike color temperature ratings - which are sometimes best to be in the 2000 - 2200K range, and sometimes in the >6500K range, depending on the stage of growth - PAR should always be high in grow lighting applications. Unfortunately PAR rating are very rarely listed on lamp packaging, so they must looked up elsewhere. One major perk involved with the use of CFLs as opposed to high intensity discharge lamps (high pressure sodium or metal halide), is that CFLs (and fluorescent lighting in general) has a higher PAR than standard high intensity discharge lamps, although high PAR versions of both types of high intensity discharge lamps are available - at respectively high prices.

    (1) http://www.elightbulbs.com/catalog_...&list_source=&portal_type=&search_type=&ansi=

    (2) http://www.elightbulbs.com/catalog_...&list_source=&portal_type=&search_type=&ansi=

    (3) http://www.elightbulbs.com/GE-43828-MVR400-U-Metal-Halide-Light-Bulb
    (4) http://www.elightbulbs.com/TCP-01836-28027M65K-Twist-Screw-Base-Compact-Fluorescent-Light-Bulb

    (5) http://www.elightbulbs.com/catalog_...&list_source=&portal_type=&search_type=&ansi=

    ravenraybill Member

    No, blue would be 6500K

    mr2shim Well-Known Member

    Says the guy who bumped a two and a half year thread. :roll:
    Mr Z

    Mr Z Member

    Great information!
    Thank you for contributing check out my grow PC :) just built from Aus:

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