Of the inter-related factors for indoor plant growing, grow lights are the most important. The most important part of lighting, is the light bulb. We sell three types of grow lights: ceramic metal halide, pulse start halide, and hortilux super hps. When considering which type of bulb to buy, the main features to look for are spectrum and output. For additional investment, you can fine-tune the spectrum to the stage of plant growth, and/or spin the lights.

High Pressure Sodium (hps)
is high output, but not full spectrum. Premium hps like Hortilux are super, that is, higher output than standard hps. This higher output gives them a little more blue than standard hps, but not optimal levels for most varieties of plant types.

Quartz Metal Halide
can be spectrum-enhanced, like Sunmaster, but are not true full spectrum like ceramic metal halide. To slightly enhance output of standard halides, output is sacrificed. Many are not even super bulbs (position-oriented), but are universal position, which sacrifices another 10% of the output. Standard Metal Halide bulbs do not operate very efficiently in the horizontal orientation even if they were super.

While it is true that a 1000 watt light is the highest output, a single point of light would concentrate the light too much in one small spot, instead of evenly distributing over a larger area. Right below the heat zone around a bulb, is the zone of too-high intensity. This can best be measured with a light meter. Probably the optimum level of intensity is 4300 foot candles; 5500 foot candles would be the maximum and not all varieties want 5500 fc under all environmental conditions.

Generally, two 400 watt cmh will outperform any 1000w light, because the number of angles of light is doubled (leading to less shadows on leaf surfaces), the spectrum is better, and heat is less.

Fewer watts leads to lower room temperatures and prolongs equipment life. A room temperature of 76F is optimum for the light-on period. The best way to improve light distribution and lower temperature is to spin the lights at a rapid rate.

Fine-tuning Spectrum for Different Stages
Different portions of the spectrum perform different functions. Blue light has the highest energy level, reduces stem elongation, increases rooting, and induces growth hormones. Red light has the greatest ability to bounce and penetrate the leaf canopy, increases growth of leafs and buds, and induces blooming hormones.

The plant cannot overdose on plant hormones; excessive amounts are simply stored. That is why you can use a full spectrum light for all stages. However, by enhancing relevant portions of the spectrum depending on the stage, you can increase efficiency of plant growth.

Pulse-start metal halides are more efficient than standard metal halide. They require a special ballast; standard halide ballasts won't work for them. Life Light makes PSMH Ballasts in four different spectrums, for these stages: cutting stage: 4K most of growth stage: 6.5K last week of growth stage: 4K most of bloom stage: 3K last week of bloom stage: 10K

These Life Lights are full-spectrum, with a particular emphasis depending on what is needed most at each particular stage.
The 6.5K spectrum is blue-enhanced. This will maximize the growth hormones and rooting.
A week before starting the bloom stage, switch to 4K, to slow down production of growth hormones. Otherwise, excessive stem elongation would probably result.

The 3K spectrum is red-enhanced. This will maximize the bloom hormones and over-all growth.

The last week of bloom, switch to 10K. This will maximize yield and quality. You may also increase light-on period to 20 hours, to increase the amount of light received per day. One week of blue and long day light would not be enough to revert the plant back to the growth phase.

People often make the mistake of thinking, if they use electronic ballasts or the latest Rube-Goldberg device, they are the most advanced. However, you will get better results with a good bulb even with a magnetic ballast, than you will with a mediocre bulb with an electronic ballast. Ideally, you want both a good bulb and an electronic, with rapid spinning. That narrows the choice| considerably, as not all electronic ballasts run all types of bulbs.