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My :twocents:
I've been using CFL's the whole way until now.
I added a 70 HPS after finding this chart showing a plant sensitivity relative to spectrum.
I'm a layman here but this is what I gather. My CFL's are 2700K while my HPS is 2100K(a more usable spectrum). I'll start flower on CFL but finish under both. Heat in a small space is an issue for me too, but when I look at my "warm" CFL's next to the HPS its obvious.
go and buy a 50w hps flood light at home depot for 35$ that would do much better.You would have to wire it up with some wire nuts,120 v plug and some eletric tape,thatll do much better.
PAR is not accepted by all growers as being accurate (many think it's something that bulb manufacturers came up with). At any rate, in calculations I've made, the difference between PAR and lumen output is small, and PAR values are rarely given. And lumens are not given by watt; watts have nothing to do with light/ Watts are measures of energy; they say how much energy your light source uses. You can determine efficiency in terms of lumens per watt.
Which gets to the next point...One difference between CFL and HID lighting is that HID lighting is much more efficient. HPS usually produce a minimum of 100 lumens per watt; that's 40% better than CFLs, which are around 70 lumens per watt, regardless of size. But if you've got a small are, as others have noted, HID lights can cause as many problems as they create. If you're in an area of 3 sq. ft. or under, you may be better off with CFLs. You don't get as many heat or stress issues. But, yeah, once you go beyond that, HPS is always going to be more efficient...what people might call ??better.?
As long as you're getting 5,000 lumens per sq. ft. and are pretty good about conserving the light you have (reflectors, reflective walls, etc.), you're going to get good results. And, sure, a small HPS and some CFLs will do very well.
Lumens (luminous flux) is the amount of light that humans see. If you want to measure what a plant sees, you need to measure radiant flux.
You can veg with anything. The best wavelength for veg is, well look at the chart. You cannot bud with anything. It must be the proper wavelength or you do little better than vegging. You can have thousands of LED's, several CFL's, or one HPS give you the same yield. Use whatever is the best for your situation. Just choose the proper color for the stage of development your plants are in.
From here: http://boards.cannabis.com/indoor-gr...growing-2.html
Any light will grow weed, but how much do you want for your efforts? Most all the CFL lights you will find in stores are 2700K. These are reddish, and the second best wavelength for budding, and about half the price of bluish bulbs for vegging.
Ultimately you want a mix ratio of about 85/15% in both veg and bud, but that's just tweaking it a little and not necessary.
Vegging (blue):
first choice: 5700K
second choice: 6100K
Budding (red/orange):
first choice: 2500K
second choice: 2800K
These numbers give your plants a chance at peak chlorophyll activity. Until someone shows me a better way, this is how I will determine what K of light to buy. Also notice from the graph that numbers in between the first and second choices drastically cut down on chlorophyll activity.
I would not look for the bluish bulbs in your stores, unless you happen to have a light bulb store or a hydro shop close by. The best way to find the proper numbers for both veg and bud bulbs is by searching the internet. You can get some really powerful ones this way too, much bigger than in the stores.
Look on the manufacturers web site for their spec sheet and compare it to the model on the bulb, or call them. If it doesn't say anything on the package about daylight, or cool, or K, then it almost certainly is 2700K, the cheapest and most common.
Great info about the ??right? color of light to use. About lumens/radiant flux...remember that humans can ??see? light in the wavelengths that plants use. So, realistically, luminous flux is adequate for determining light plants can use too. Light wavelengths between 380 and 760nm are, in general, visible to the human eye. Plant chlorophyll mainly absorbs light in the 400 to 700nm range (400 to 450 is red wavelength; 625 to 700 is blue). So, while radiant flux is technically correct, luminous flux does the trick awfully well for determining if you've got enough light.
This kind of gets back to the PAR thing...PAR is a measure of radiant flux (active photons) over a specific area. You need about 135 PAR watts per square meter for a really good grow. A typical 400w HPS gives off about 125 PAR watts, which means it should do a good job on .926 of a square meter. If you look at lumens...a typical 400s HPS gives off about 50,000 lumens. You need about 5,000 lumens a square foot to get a very good grow, and a square meter is 10.76 square feet. Using lumens, you get a figure of .929 of a square meter. Very, very close. I always tell people to keep it simple, and since lumen output is given for a lot of bulbs, it's the easiest way to figure if you've got enough light. Just my .02 on that.
And, like you said, you just want the right type of light with enough output. Factors like closet size, ventilation, etc. may make one type of light better or worse for someone.
True. True.