Choosing an HID Light Systems
1. Determine the size of your growing area. Here are some guidelines for lighting coverage in your growing area. You may exceed these recommendations by quite a bit: you cant have too much light in your indoor garden (especially HPS light), however, you can have too much heat. I recommend venting your light. Consider the amount of space your plants need and fill that area with light based on the diagram below.
400w approx. (3x 3)-(3x 4) OR 9-12 square feet.
600w - approx. (3x 4)-(4x5) OR 12-20 square feet.
1000w approx. (4x 5)-(5-8) OR 20-40 square feet.
2. Determine what kind of light you need. If your growing area has no outside light, metal halide (MH) provides the most energy to your plants. If you have a strong source of natual light (such as a greenhouse or sun room), high-pressure sodium is the best supplement. Special lamps can enhance and broaden spectral output and improve spectral balance. Enhanced metal halide lamps provide up to 38% more yellow-orange-red light while sodium can be augmented with up to 25% more light in the blue spectrum. A metal halide is good for veg and a high-pressure sodium is the best for flowering. If you can affored both then just get a hps and it will work. If you cant affored any of them then your best bet would be to get some cfls.
3. Determine the reflector style you prefer. When choosing a reflector consider the area you would like to cover and the required light intensity of the plants you are growing. Keep in mind that a deep reflector will concentrate the source on your garden below. A shallow reflector will disperse light over a wider area but it will be less intense where is falls. Choose a system with vents and a tempered glass lens to eliminate heat build-up in your garden room. A lens also protects the lamp from dust and water.
4. Choose the correct lamp. Lamps must match the type (HPS or MH) and wattage of the ballast. You cannot use a metal halide lamp in a sodium system or vice versa. Choose a conversion lamp if you want sodium light and have a metal halide system or have a sodium system but want a halide spectrum. Two-way ballasts use both a HPS and a MH lamp, just select the correct wattage.
If I made any kind of mistake then please let me know and I will change it.