hydroponics grow light

What is a Metal Halide Grow blub? Metal halide grow lights are a type of HID, or high-intensity discharge, lighting. These lamps contain a quartz tube filled with a noble gas. An arc of electricity is sparked between two electrodes inside the tube to create light. MH bulbs contain metal halide. This gas burns with a cool white light that contains a large amount of light in the blue wavelengths. Metal halide bulbs can last up to 20,000 hours, although they degrade to the point that they are no longer effective as grow lights long before that. They have a high lumen output and also generate a lot of heat. Overall, MH bulbs are highly efficient, though they are not as efficient as HPS (high-pressure sodium or CMH (ceramic metal halide) bulbs. Note that ceramic metal halide bulbs, while they sound similar, are actually quite different. I will go into detail on the comparison toward the end of this article. Spectrum of a Metal Halide Light Before we see and compare the spectrum o...

What light do plants really absorb? In the 1970s a scientist called McCree determined the wavelengths of light a plant can absorb. He assessed the relative quantum efficiency of different wavelengths of light on photosynthesis. In other words he recorded the rate of growth of plants exposed to each wavelength or colour of light. McCree discovered that plants use all parts of the PAR spectrum but at different rates. The quantum efficiency for red is close to 100% efficient whereas blue and green were less efficient, ranging from 65% to 75%. McCrees action spectrum identifies what colors of the visible spectrum are best for photosynthesis. McCrees action spectrum is the correct reference for assessing the suitability and effectiveness of a grow lights spectrum output. Blue Light Blue lights with a Kelvin color temperature from 5000K to 6500K or wavelength in the 400-500 nanometer range are best for the vegetative stage of the grow cycle and for starting seeds indoors. This color range...