plainsman1963

Sometimes, I have nightmares over seeing that sentence one more time...

What with classes letting out and outdoor grow season here in my neck of the woods kicking off, I am sure there are going to be many new members/guests showing up with that question on their minds.
Outdoor the answer is a bit simplier. Plenty of sun.

For indoor growers, we first must recognize the three basic types of lighting you can use.
#1. Fluorescents.
#2. High Intensity Discharge (HID) lamps.
#3. Sunlight.
If you do not have one of these 3 to utilize, please read the lighting section of the grow guide , and Why incandescent lights suck . You can catch up to us when you have access to one of the big three.

Sunlight I won't even get into because unless you have a Southern facing room (again, for my neck of the woods) with the South wall filled with windows that noone can see into and you can convert to a grow room...Or...You have a loft with glass ceiling panels, imho, 99.9% of the time you just can't do it.
Greenhouses are a type of indoor growing though. Just not in my field of experience.

Fluorescents are the picked on light of this generation.
I have been fortunate enough to live through 4 decades and back in the 70's these lights were the top dog.
4 foot shop lights, cool white bulbs. As many as you could fit. Stealth wasn't quite as possible by today's standards.

Nowadays, you have a wide range of spectrum to choose from. So you can better match your tubes to the type of growth.
4 foot ballasts and tubes are really cheap, there are now compact fluoro's that are more expensive. With these you have more lumens in a smaller space, which is always a good thing.
Envirolites and Lights of America are two of the more popular compact fluorescents.

If your grow requirements dictate you use fluorescents I can respect your right to make that decision.
If you believe your wallet dictates you use fluorescents, in my opinion you will find yourself spending the same amount of money upgrading your fluorescent grow over the long run as you would getting a small/medium HID light.
Here , here and here are some good data sources for fluorescent watts/lumens/kelvin temperature.

For those of you who feel put down for using your fluorescents, hold your head high. Many good grows have been the result of fluo's and you are continuing a tradition that has spanned decades.
One light at the end of the tunnel. Something somewhere (new age led's, solar cells, etc...), will be the "new breakthrough technology" and kick the HID growers out of the top spot someday.

High Intensity Discharge lights come in three flavors.
Mercury Vapor (MV): From my experience, better than everyday fluorescents (cool white, warm white). Spectrum isn't the greatest to say the least. Better for vegging than flowering by a long shot. Heat is a problem and they are inefficient as all get out.

Metal Halide (MH): Next light up in the HID chain. Good vegetative light. Falls short for flowering.

High Pressure Sodium (HPS): Top dog at the moment. Great for flowering and many growers are discovering they can be used for entire grows, eliminating the need for other lights.
Here is a great thread with the debate and here is a good thread comparing MH and HPS.
Conversion bulbs are available so you can switch from HPS to MH or vice-verse as well as "expanded spectrum" bulbs that will give you a wider spectrum HPS or MH.

Here and here are a couple of other sites besides Lamp Lumen Data to get data on HID lights.

Now we have covered what lights to get, we can get to "do I have enough light?".

__________________
Good Growing,
Plains

"In my many years I have come to a conclusion that one useless man is a shame, two is a law firm, and three or more is a congress."
- John Adams

plainsman1963

Some people figure out their lighting requirements using watts, some figure using lumens. Since this is a basic kind of posting I am not going to delve into PAR [used to be what we strived for in golf, go figure. ] or PGRE(plant growth radiant efficiency). If those interest you have a look at the Tazawa study Part #1 and part #2.
I personally figure using lumens. I add watts when I want to figure out my electricity bill.
From the lighting section of the grow guide :
So you can get your lumens from your bulb/tube. If you don't know it, again reference the Lamp Lumen Data thread and look it up.

Figuring lumens one thing you have to take on faith is the manufacturers lumen claim. We are just going to use it for a base anyway. The only true way to figure out your lumens per sq. foot is to utilize a high quality light meter. Failing that, we can get a general idea using the above formula.

Once you have figured out your lumens for your grow space, keep in mind it is theoretical. You will be losing lumens with the placement of your lamp, with your reflector and your reflective material you utilize. This is why I try to achieve 7,000 lumens per sq. ft. minimum. Not having a light meter, I figure even if I am only getting 3,500 true lumens per sq. ft. it is above the minimum suggested in the literature. This is just my way of getting in the ballpark.

So to sum it up. Do you have enough light? Follow the formula I posted from the grow guide, if you don't have a light meter, err on the side of caution and cut it in half to be safe and you can answer your own question...

One final note: Most of what I have learned, I have learned from this site and the outstanding gardeners on these boards. If I have something wrong, it is the fault of the student and his ability to learn, not the fault of the teacher.

Good growing,
Plains

__________________
Good Growing,
Plains

"In my many years I have come to a conclusion that one useless man is a shame, two is a law firm, and three or more is a congress."
- John Adams

St0ney

I'm such a stoner.

__________________

plainsman1963

Umm....St0ney? It's the third blue link in the first post.

__________________
Good Growing,
Plains

"In my many years I have come to a conclusion that one useless man is a shame, two is a law firm, and three or more is a congress."
- John Adams