Educational guides for buyers and manufacturers. Every guide cites authoritative sources (DLC, university extension research, ASABE standards) and is written to help you make better grow-light decisions — not to sell you a particular fixture.
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Understanding PPF, PPFD, and DLI
The three units that actually measure what a plant receives. Why lumens and watts don’t work, and how to compare fixtures correctly.
~1,700 words · Foundation
LED vs HPS vs CMH: A Buyer’s Guide
An honest comparison of the three dominant technologies. Where each one wins, where each falls short, and how to choose based on your room, crop, and budget.
~1,900 words · Buying decisions
How to Read an IES File
The photometric data file that actually backs up — or contradicts — a manufacturer’s marketing claims. What’s inside one and what you can extract.
~1,600 words · Technical reference
How to Calculate Coverage Area
“Covers 5×5 ft” at what PPFD? At what mounting height? Compute the real, usable footprint of any fixture for your specific crop and stage.
~1,600 words · Practical guide
Spectrum Basics for Each Growth Stage
What wavelengths matter at each stage, why “full spectrum” doesn’t always mean what manufacturers claim, and how to read an SPD graph.
~1,600 words · Cultivation
Grow Light Efficacy (μmol/J) Explained
The single most important number for long-term cost. What efficacy actually measures, current benchmarks, and how manufacturers inflate their claims.
~1,500 words · Cost analysis
More Help
- Use our Grow Logic calculator to get fixture recommendations for your specific room and crop.
- Browse the verified directory filtered by light type, manufacturer, or specs.
- Read how we verify — the in-house IES audit process and what each badge means.
If there’s a topic you’d like a guide on that we haven’t covered yet, let us know.