Originally published in GROW magazine.
Under artificial lights, things aren’t always as they seem. It’s why the smokeshow you brought home from the club last night looks haggard the next morning. Blame it on the beer goggles, but the real culprit is probably the light. And though you might be able to laugh off an alcohol-induced oversight, you won’t be laughing if the crystals on your crop turn out to be powder mold.
Lighting used for indoor growing operations distorts color, often making plants look different than they do in natural light. Exposure to these lighting systems also strains the eyes, causing headaches, migraines, fatigue, and dry eyes. “The light is so extreme, it makes it hard to do your job,” says Dave Iacovelli, National Sales Manager for Method Seven Specialty Optics. An industry leader in cannabis cultivation eyewear, Method Seven designs products that balance the light spectrum while protecting growers’ eyes from harmful light and infrared heat.
Average sunglasses are dyed pieces of plastic, which offer some UV protection, but do nothing to safeguard your eyes against infrared heat, or color correct for lighting conditions in your grow. Method Seven utilizes a technology called notch filtering, which cuts light at specific wavelengths depending on the lighting scenario.
Shedding Light on the Subject
High pressure sodium (HPS) lights, the most popular system for large grows, are renowned for consistently high yields. However, they also produce high levels of infrared heat, which is straining to the eyes. And as Iacovelli points out, the reddish yellow hue cast by HPS lights often makes plants look nutrient deficient when in reality, they’re perfectly healthy. The color-rendering index (CRI) of HPS lights is 26-28% for 1,000W, meaning that almost three-quarters of visual information is distorted or obscured. “HPS has always been the standard but it’s missing a key part of the spectrum,” says Shawn Sullivan, Pacific Northwest Sales Rep for Nanolux, a horticultural lighting brand.
Metal halide (MH) lights are often used in combination with HPS in order to fill out the blue/purple side of the color spectrum. The CRI for MH lights is still fairly low, though: only 65% for 6,000W. And like HPS, MH lights produce a significant amount of infrared heat, fatiguing the eyes and compromising vision.
Ceramic metal halide (CMH) lights produce crisp white light, and with a CRI of 96-97% (for 3,000 and 4,000W, respectively), they offer better visual clarity than HPS or MH. Unfortunately, that doesn’t mean that this type of lighting is any better for your eyes. CMH emits large amounts of ultraviolet (UV) light. This stresses plants, making them heartier and triggering production of turpines and THC. However, the effects of UV exposure on humans include cataracts, macular degeneration, pingueculae, pterygia—and skin cancer.
HPS, MH, and CMH are available in two different forms: single enders and double enders. While single enders are primarily used for growing on the hobby scale, double enders are the standard for large grows, and emit light at a much higher intensity. “Everybody wants that great spectrum, but you need the intensity to get your yield,” says Sullivan. He stresses the importance of wearing a long-sleeved shirt, a hat, and especially sunglasses when working under double ended lights. “Double enders are terrible for your eyes,” he cautions.
Light Emitting Diodes (LEDs) generally operate at low heat and emit minimal amounts of UV, though some manufacturers are experimenting with enhancing the UV spectrum. A standard full spectrum LED has a CRI of approximately 85%, meaning that it reliably represents plants’ true color. Still, LEDs do pose some threats to eye health. “There are intensities of lights where you get to a point that it’s so bright you can do some damage,” admits Dr. Dave Hawley, Senior Scientist at Fluence. And LEDs with specific color spectrums (like magenta) tend to cause eye strain. “Once you’re under pink light for 8 hours a day, when you leave that environment, its so jarring,” says Hawley. “You feel like an alien.”
Don’t Grow Blind
Utilizing notch-filtering technology, Method Seven offers protective eyewear customized for each type of grow light. Their original product, a mineral glass lense, delivers “Perfect Color” in HPS lighting. Method Seven also offers eyewear specific to MH and LED lights, including green color lenses for magenta LEDs. For CMH, Iacovelli recommends the Agent 939—the first polycarbonate lense in the world to filter out infrared heat.
Color correction specific to each light spectrum and CRI makes it easier to spot things like pests, powder mold and nutrient deficiency. Historically, growers have taken clippings outside in order to accurately assess plant health. However, as Hawley points out, “commercial growers aren’t pulling every plant out of their facility and putting it under normal light just to see what’s going on. They’re probably going to miss something.”
Iacovelli encourages growers to think of the lenses as a tool not only for maximizing yield, but also in terms of comfort and safety. “All of our glass lenses filter out infrared heat, which keeps the eyes moist,” he says.
Whether you’re working under HPS, MH, CMH, or LED, “you’re basically replicating the sun at a 12-foot scale,” says Sullivan. “People are spending more and more time in rooms with light than they ever did before. I think we’ll see the effects 4-5 years down the line.”