The Science Behind Method Seven Grow Room Glasses: How Our HPS Lens Technology Was Originally Developed

For more than a decade, Method Seven has led the industry in protecting the vision of growers working under extreme indoor lighting. Back when High Pressure Sodium (HPS) dominated grow rooms, the company invested in rigorous optical science to understand how this harsh light spectrum affected human vision — and how to correct it.

The document below is part of that early research. It demonstrates, in detail, the scientific testing used to create the original Method Seven HPS lenses. These tests covered color perception, the rod/cone response, scotopic vs. photopic balance, the strobe effect, and the clarity differences between mineral glass, polycarbonate, and typical sunglasses.

Although grow lighting technology has evolved dramatically — with today’s full-spectrum LEDs producing new and even more complex visual risks — the foundation remains the same: deep optical science, real instrumentation, and rigorous human-factor testing.

This is why Method Seven became the leader in grow room glasses.And this same scientific approach is exactly what drives the next generation of Method Seven lenses designed for modern high-intensity full-spectrum LEDs, which can be even more harmful to human eyes than early HPS systems.

The following is a restored and reformatted version of the original Method Seven HPS white paper, preserved for growers, engineers, and professionals who want to understand the roots of this technology and how much engineering goes into helping people see clearly and safely where plants thrive most.

---

EVALUATION OF METHOD SEVEN OPTICS UNDER HPS LIGHTING CONDITIONS

Overview

High Pressure Sodium (HPS) lighting is efficient for industrial applications and grow room environments, but it creates difficult visual conditions for humans. This paper evaluates:

• Color perception
• Ability to focus on shapes and motion
• Effects of the HPS strobe flicker
• Visual clarity

Testing was performed with:

• Naked eye
• Method Seven HPS (mineral glass) lens
• Method Seven HPS Zeiss polycarbonate lens
• Premium glass-lens sunglasses
• Popular polycarbonate sunglasses

HPS lighting emits a narrow band of yellow light (~590 nm). Humans see best in Balanced White Light (BWL), which spans 390–750 nm. Because HPS lacks blue light (~505 nm), our rods and cones do not receive the balanced light needed for natural color and clear motion detection.

---

COLOR PERCEPTION TESTING

Method: Middle Grey Target (X-Rite ColorChecker)

Using a Canon 5D Mark II and an X-Rite Digital Color Chart, Method Seven measured RGB values reflected from a calibrated 18% grey target.

• Balanced white light (BWL): R=160, G=160, B=160
• HPS naked eye: R=214, G=138, B=0 (strong yellow/red shift)

With Method Seven lenses:

• Mineral Lens (glass HPS)
• R=149, G=145, B=142 — very close to the true grey reference.
• Zeiss Polycarbonate Lens
• R=183, G=121, B=84 — improved but not as balanced as mineral glass.
• Sunglasses

Both glass and plastic sunglasses further degraded color balance because sunglasses remove more blue than yellow.

Color Balance Score Table

---

KELVIN TEMPERATURE MEASUREMENT

Using a Kenko KCM-3100 Kelvin color meter:

Conclusion: Method Seven lenses shift HPS lighting toward natural daylight, restoring color perception.

---

FOCUS AND VISUAL COMFORT UNDER HPS

In the 1980s and ’90s, researchers at Lawrence Berkeley National Laboratory (notably Dr. Sam Berman) discovered why HPS lighting caused headaches, nausea, and visual fatigue in warehouse workers:

• Cones (≈7 million cells) respond to yellow/orange (~555 nm)

• Rods (≈120 million cells) respond to blue (~505 nm)

HPS over-stimulates cones and under-stimulates rods, degrading:

• Focus

• Depth perception

• Motion detection

---

SCOTOPIC / PHOTOPIC (S/P) RATIO TESTING

Ideal indoor S/P ratio: 2.0
Natural sunlight: 2.5
HPS lighting: 0.6

Measured with SolarLight SnP Meter (SL3101):

Meaning: Method Seven lenses significantly improve shape and motion detection under HPS.

---

THE STROBE EFFECT

HPS lighting flickers with AC voltage cycling. Humans don't consciously see this, but:

• It contributes to headaches

• It degrades comfort

• It causes video banding

Rendition Lens: eliminates the strobe effect
Zeiss Polycarbonate: significantly reduces it
Sunglasses: minimal reduction

---

VISUAL CLARITY

• Method Seven glass lenses use elements bonded into the crystal structure — no dyes, no emulsions.

• Zeiss polycarbonate lenses, co-developed with Carl Zeiss, also maintain excellent clarity.

• Most sunglasses — especially polycarbonate — introduce distortion and dullness.

---

SUMMARY OF RESULTS

Method Seven surveyed growers to weight what matters most:

Overall Conclusion

Method Seven HPS lenses dramatically improve:

• Color accuracy

• Focus

• Motion detection

• Comfort

• Clarity

Sunglasses, in contrast, make HPS visual conditions worse.

The science in this document reflects where Method Seven started — but it also explains exactly why we are where we are today. From the beginning, our approach to grow room eyewear wasn’t about making sunglasses with a different tint. It was about understanding light at a molecular level, how it interacts with the human eye, and what growers truly need in the environments where they spend their lives.

Those early tests under HPS weren’t just “research.” They were the foundation of a philosophy: give growers the clearest, safest, most accurate view of their plants, and do it through real optical engineering — not shortcuts. That same mindset is core to who we are now.

The grow room has changed. Lighting has changed. Full-spectrum LEDs introduce new intensity levels, new spectral peaks, and new long-term risks that didn’t exist during the HPS era. But our standard hasn’t changed. We still engineer every lens through rigorous testing, scientific measurement, and field validation — the same process that made Method Seven the leader in HPS protection. And now, those same standards guide every next-generation LED lens we’re building.

Growers rely on their vision as their most important tool. Method Seven exists to protect that. Whether under legacy HPS or ultra-bright modern LEDs, our mission is the same: deliver uncompromising clarity, true color, and real protection — so growers can see more, perform better, and stay safe for the long haul.

This research is where it all began. But its impact is still shaping the future of everything we build.