What type of light ?
Some good info....from WW..
Types Of Indoor Lighting
Lighting is the single most important factor in an indoor garden and often requires the biggest financial investment. It's important to set up an adequate and cost effective lighting system, and it's also important to understand the different types of bulbs available, as well as their functions, strengths, and limitations.
High Intensity Discharge Lighting (HID)
These powerful lamps generate light by passing electricity through gas under high pressure, unlike fluorescent bulbs that utilize low-pressure gases, and standard incandescent bulbs that pass current through a wire filament. For HID bulbs, the gas in the tube and the coating on the bulb determine the spectrum of light emitted. All HID lights work on these principles and require special ballasts (transformers and capacitors) and sockets to operate. Though they come in a variety of wattages, most gardeners recommend 400, 600 or 1,000 watt HID bulbs. Note: Line voltage, operating characteristics, and physical shape are unique to each lamp. Never mix and match ballasts with lamps!
Mercury Vapor
These pioneering HID lamps were invented around the turn of the nineteenth century. By today's standards though, these lamps are inefficient and expensive to operate.
Metal Halide (MH)
MH lights are the best single source for indoor garden lighting. Standard MH lamps produce light from the blue end of the spectrum. "Corrected" MH bulbs, however, produce balanced spectrum light similar to tropical sunlight, and contain both the red and blue wavelengths plants need for rapid growth. In a room with no outside light, start plants under MH lights until the vegetative growth stage is over.
High-Pressure Sodium (HPS)
HPS is the most efficient light source. 1 lumen = the amount of light emitted by one candle that falls on one square foot one foot away. One 1,000 watt HPS bulb can produce 140,000 lumens, or the most lumens per watt of any HID bulb. HPS light emits mainly in the red and orange region of the spectrum, and promotes excellent fruit and flower production. The lack of blue spectrum light, however, can cause plants to become "leggy" if used alone during the vegetative stages of a plant's development. Many gardeners start plants under MH lighting, and then switch to HPS for fruit and flower development.
Note: HPS lighting is the perfect supplement to natural lighting and is ideal for extending the photoperiod in your greenhouse or sunroom.
Conversion Bulbs
The ideal lighting system includes both MH and HPS lamps. To spare the expense of two systems, however, conversion bulbs are your best option. HPS conversion bulbs run off an MH ballast and emit more lumens and red spectrum light than a metal halide bulb in the same ballast. You can start plants under MH lamps, and then switch to an HPS conversion bulb for flowering.
Metal halide conversion bulbs offer the opposite approach; you start with an MH conversion bulb, and then switch to a regular HPS bulb for flowering. If you want only one type of bulb for all stages of growth, you can use an enhanced or "corrected" HPS bulb. These lamps provide a more balanced spectrum than standard MH or HPS bulbs.
Fluorescent Lights
Traditionally used for propagating seeds and cuttings, fluorescents are also suitable for growing plants to maturity and often preferred for their efficient operation, reduced heat output, bloom and grow versatility, and minimal space requirements.
Tungsten Halogen, Iodine Quartz, or Bromine
These standard lamps are similar to incandescents, emit the far-red end of the spectrum and are relatively expensive to operate with low lumen- to-watt output. While they run on standard 110-volt current and don't require a ballast, they're a poor choice for the indoor gardener.
Low Pressure Sodium (LPS)
Low-Pressure Sodium are available most often in low wattages; although their lumen-to-watt output is the highest of any lamp, they function on a very narrow band on the yellow color spectrum which provides limited use to growing plants. While LP sodium lights maintain 100 percent of their lumen output throughout their life spans, they must be used, if at all, with an MH lamp to stimulate photosynthesis. Most indoor gardeners highly recommend HPS over LPS lamps.
Bulb Replacement
Replace HID bulbs after 12 to 18 months of use. HID lamps will continue to light beyond 18 months of use, but will have lost up to 30 percent or more of their lumen output while consuming the same amount of electricity. These lamps contain some harmful materials so don't throw them into your trash. Most municipalities have disposal programs to accept HID bulbs and other hazardous materials for free or with a nominal disposal fee. Never put spent bulbs in a fire. Remember that it's critical to replace bulbs with the right one for your ballast and reflector configuration.
Light Movers
Motorized light movers can improve the dispersion of your light system's output without increasing your electricity bill. The frequency of movement and stability of the set up are more important than the speed. Since the light is always in motion and doesn't rest above any part of the garden, you can move the lights closer for maximum light intensity. As the reflector moves, it directs light toward under-exposed areas, giving your plants excellent penetration through the canopy and ensuring strong development at lower levels.
Helpful Hint - Reflective Light
Get the most from your lighting system by hanging reflective material such as Mylar or Dureflect™ to reflect light back toward the garden. This salvaged light often strikes the plants at different angles, increasing the efficiency and penetration of your grow light.
Indoor Lighting 101
MH, HPS, and Two-Way Ballasts: When to Use What
When it comes to the kind of light they will use to photosynthesize, most plants are pretty picky. Although the sun offers a wide spectrum of light, plants really only respond to the blue and red ranges of that light spectrum.
If it's mostly vegetative growth you're after, metal halide lighting is the type of HID lighting you need. Similar to the sun's rays in spring and summer, metal halide lamps produce light which is mostly in the blue range of the light spectrum—that's what you need to grow lettuce, basil, and other leafy greens. Metal halide lights come in all kinds of sizes. Lamps that are just 250 watts and even smaller are available; however, small wattage lamps are not usually as energy efficient as larger ones, and you'll be left with a much smaller growing space and less light intensity. Most indoor growers choose 400- or 1000-watt lamps because they provide a lot of light very efficiently.
If you want to encourage your tomato plants to fruit indoors, you'll want to use a high pressure sodium lamp. By emitting light from the red-orange region of the spectrum, this sort of HID lighting simulates the sun's light in fall. Plants under a high-pressure sodium light think its time to finish their growing cycles so they make flowers and fruit.
People with greenhouses sometimes supplement the sun's light with high-pressure sodium lamps to promote blooming. But high-pressure sodium all by itself is not really suited to promoting overall vegetative growth indoors because it lacks the blue part of the light spectrum. For that reason, some gardeners use both metal halide and high-pressure sodium types of HID lighting simultaneously. Others encourage vegetation with metal halide and then finish with high-pressure sodium.
As with metal halides, high pressure sodium lights are available in many different wattages, and, again, lamps that are 250 watts and smaller are not as energy efficient and will not provide the greatest coverage or light intensity. The most commonly used sizes are 400, 600, and 1000 watts because they are among the most energy efficient.
Obviously your indoor plants would love to have plenty of blue- and red-spectrum light, but that doesn't mean you have to have two different lighting systems just to suit them. If you have a metal halide light, you can get a special high-pressure sodium conversion bulb that will run in your system and emit red spectrum light. That means you can start plants under a standard metal halide lamp and then put in a high-pressure sodium bulb when it's time for fruiting and flowering. On the other hand, if you have a high-pressure sodium lamp, you can use a metal halide conversion bulb in your system to emit light from the blue part of the spectrum. Because the conversion process itself takes some energy to accomplish, conversion bulbs aren't quite as efficient as regular metal halide or high pressure sodium bulbs, but they will give you the best of both worlds with just one light system.
Some other good options are two-way ballasts and electronic ballasts. Two-way ballasts can actually be switched back and forth depending on your needs at the time. If you want a metal halide lamp, you put in a regular metal halide bulb and switch the ballast to its metal halide setting. For high-pressure sodium, you put in a regular high-pressure sodium bulb and switch the ballast to the high-pressure sodium setting. An electronic ballast, on the other hand, operates on advanced technology that eliminates a switch altogether.
Focus on Fluorescents
In the past, horticultural fluorescents were only used to start seeds and cuttings so it's not difficult to understand that many gardeners believe this is still the case. What's changed? The most notable difference is an increase in light intensity. Light intensity is generally measured in lumens, and some of the newer, high-wattage fluorescents can emit over 10,000 lumens each, giving systems like the Sunleaves Satellite IV Grow the power of more than 40,000 lumens. To put this into perspective, consider the 20-watt fluorescents that deliver a whopping 975 lumens and the 95-watt compact fluorescents that put out about 6,000 lumens. Because most plants require at least 10,000 lumens for continuous growth and development, it's no surprise that the older-style fluorescents are limited to propagation.
Knowing that fluorescents are indeed capable of growing plants to full maturity, it's only natural to wonder how they might compare to traditional high intensity discharge (HID) systems. You might be surprised to hear that fluorescents are actually surpassing HID's in many respects. For one, they house the ballast internally so the fixture is the only system component to deal with - HID's require a ballast separate from the reflector and bulb portion. This simple design also makes fluorescent fixtures more suitable for confined spaces and it gives the user the option of hanging units vertically as well as horizontally.
Other features of high-power fluorescents? They run both grow and bloom type tubes (think metal halide and high-pressure sodium respectively for HID's) that can be used separately to accommodate the specific vegetative and flowering stages or simultaneously to create a more balanced light spectrum. And where high intensity discharge lighting is notorious for generating a great deal of heat that requires ventilation, fluorescent heat output is substantially lower. This is advantageous in that the fixture can be much closer to plants without danger of scorching - a characteristic that also proves beneficial with regard to light intensity. Because light intensity decreases exponentially with distance from the light source, fluorescents can compensate for HID's higher lumen output by staying closer to the plant canopy.
When it comes to cost considerations between the two systems, keep in mind the initial investment as well as maintenance and operational costs. Certainly choosing top-of-the-line or this-will-do-just-fine components influence the bottom line, but generally speaking it costs about the same to purchase either system. The gap increases when financials are evaluated over the long haul, because even though the lumen output of any lamp decreases over time, fluorescents outperform HID lamps by maintaining performance levels for years rather than months.
Finally, HID's usually take the cake when it comes to covering a larger grow area and because they're time-tested and proven performers, multiple-year product guarantees often accompany new purchases as opposed to many new fluorescents that offer limited warranties.
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