Brighter light is not always better for gardening

Today, in early 2013, if you've searched the INTERNET for information on lighting for indoor gardens, you have no doubt read the opinions of a lot of people. While much of what you read may be true, there are a lot of preconceptions that are quite simply dead wrong.

These incorrect presumptions about how light and plants interact continue to prevail simply because at first glance it makes sense, and more and more people share their "knowledge". Such is the case with the myth that a brighter light is always better for growing plants. To set the record straight, higher wattage bulbs DOES NOT ensure bigger plants, and here is why.

We typically measure brightness in "lumens", and one lumen is about as bright as a candle flame. This is an indicator of how much white light is produced, and it is in fact a useful number when determining the lighting needs of humans, but often people forget that white light is actually a combination of all the colors of the rainbow.

The human eye makes use of the wavelengths between 350 and 900 nanometers (nm), commonly called the "full visible spectrum". By comparison, plants have evolved using only about half of the visible spectrum, in 2 sections. The blue region of the spectrum around 400 - 520 nm, and the red region, 610 - 720 nm.

In addition to length of day/night periods, plants detect the amount of red or blue in the light they receive to help them determine what season it is. In fact natural sunlight has slightly more blue in it during the spring and decreases as fall approaches. Plants naturally assume they should be growing when the light is blue dominant, and flowering when it is red dominant.

In the case of actually growing plants indoors, while High Pressure Sodium (HPS), Metal Halide (MH) and florescent lighting will almost always be much brighter to the human eye, much of the lights output is wasted, converting electricity to visible light that is outside the red and blue ranges your plants can actually use.

To further confuse home gardeners, many lighting manufacturers and retailers compare various lighting solutions by calculating the watts consumed divided by the output measured in lumens. This is fine way to measure light efficiency for humans, but is quite misleading when to comes to gardening.

Because the light generated by LED grow lights contains only portions of the light spectrum plants actually use they typically create purple light that to the human eye appears dimmer when compared to the same wattage using full white LEDs. This is the time to not believe your eyes. Brighter is not always better.

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A historic look at lighting and the LED lighting revolution.

One of the earliest known functional light bulbs was lit way back in the year 1802, by a man named Humphry Davy. The principles behind incandescent lighting had been known possibly as early as the 1760s, shortly after electricity was discovered. In a nutshell, by running electrical current through a conductor encased in a gas filled or vacuumed transparent globe of glass you create an incandescent light bulb.

Using a platinum filament, and inefficient vacuum pumps, the first lights were pretty dim, and burnt out quickly, but it was the first step of a journey that continues today, over 2 centuries later. The pursuit of efficient lighting.

33 years later, in 1835, an inventor named James Lindsay had improved upon Davey's design so that he could "read a book at a distance of one and a half feet", which is roughly equivalent to a candle flame, producing about 1 lumen. Another 20 years later in 1855, the first florescent lights were developed, but they were too expensive to produce, dim and didn't last long enough to be practical.

Finally, after another 24 years, in 1879 Thomas Edison perfects his methods, leading to a commercially available incandescent lamp for home use, however, similarities to other already patented methods would result in 10 years of litigations for him, which he eventually won. Contrary to popular belief, Edison did not simply invent the light bulb, he actually purchased the patent rights to a variety of methods developed by others, and then went to work on determining and combining the to most effective aspects of each.

All of these incandescent bulbs, including those made today are simply very inefficient at the task of converting electricity into visible light, wasting the majority of the power they consume generating infra-red light, aka heat. Even today's incandescent bulbs are estimated to be only 2-3% efficient, wasting as much as 98% of the energy they consume.

Then in 1895, 16 years after Edison's breakthrough, the first commercially available florescent lighting was produced, by one of Edison's former employees, a man named Daniel Moore . By 1904, Moore was producing fluorescent tubes that were far more efficient than the more popular Edison type bulb. They lasted longer and they produced a more "natural" light.

It was Moore's breakthrough that motivated General Electric to continue researching new ways to improve the efficiency and lifespan of their incandescent bulbs, although they are still a long way off even today. Despite their inefficient use of electricity and shorter life spans, the lower manufacturing costs of incandescent lighting made them the preferred choice for most consumers for the following 100 years.

Another 16 years after Moore's breakthrough, the first light emitting diodes, or LEDs were produced, although "Light" is potentially misleading at this point, since no visible light was produced, only infra-red. It wasn't until 1961-62 that LEDs finally produced visible light.

By 1972, the brightness and efficiency of LED lights had improved 10 fold in just 10 years, but still were not considered bright enough for home lighting applications and primarly used for electronic signs and indicator lights.

Fast forward to the year 2013 and surprisingly we still have incandescent lighting very similar to those made 137 years ago, although much of the world is phasing them out. Todays incandescent bulbs can produce 800 lumens of light using 60 watts of power, or about 13 lumens per watt. This is a tremendous improvement over the incandescent lights made over 200 years ago, but is still nowhere near as efficient as today's fluorescent lighting, such as the compact fluorescent lights (CFL) which are roughly 4 times as efficient as today's incandescents, consuming only 15 watts to create that same 800 lumens.

But today, the big winner in the realm of efficient lighting is the light emitting diode (LED), which is roughly 10 times as efficient as incandescent, and twice as efficient as CFLs. Using as little as 6 watts while producing that same 800 lumens. Some LED lights can use as little as 10% of the energy and last up to 20 times as long when compared to incandescence bulbs,

Even still, many people seem reluctant to start using them due to their higher initial costs when compared to CFL. In most cases, switching to LED lighting pays for itself within a couple of years, well within their typical 5 to 6 year lifespans.

Add to that, unlike incandescent or CFL lighting, LED lights can be tailored to produce specific wavelengths of light, and then combined to create lights for specific needs. A red and blue mix for example is ideal for indoor gardening, or a white and blue mix for operating rooms and similar environments, where seeing tiny details is crucial and a white red mix for general lighting.

UPDATE: Below is a short yet informative video which explains the basic physics behind the various types of light bulbs. ENJOY!