Light Uniformity Calculator

Why uniformity matters

Uniform light reduces stretch, uneven leaf size, and maturity gaps across benches. When dark edges persist, plants compensate by elongating, which weakens stems and complicates irrigation timing. Hotspots can stress tissue and accelerate drying. Tracking uniformity alongside average intensity helps you separate “too dim overall” from “patchy distribution,” so adjustments target layout rather than simply adding more power. It also improves harvest planning and consistent quality.

Setting up a repeatable grid

Start with a simple rectangular grid and keep point spacing consistent. Measure at canopy height, with fans and curtains in their normal positions. Record readings after lights warm up to steady output. Use the same sequence each time, moving left to right, row by row. Consistency lets you compare tests after raising fixtures, adding reflectors, or changing spacing. Mark corners with tape to avoid drifting positions.

Choosing the right metric

This calculator provides three ratios: Min/Avg, Min/Max, and Avg/Max. Min/Avg is practical for growth because it focuses on the weakest area relative to the overall field. Min/Max is stricter and highlights extreme hotspots. Avg/Max indicates how dominant the peak is. Pair ratios with coefficient of variation to capture overall spread, not just endpoints. They guide layout decisions and fixture selection.

Interpreting results and thresholds

Uniformity targets depend on crop sensitivity and distance from fixtures. For many propagation and leafy crops, a Min/Avg near 0.70 is a useful starting point. If your CV exceeds 20%, expect visible differences between zones. Review minimum values first; the lowest points usually dictate plant response. Use the chosen metric consistently so improvements are comparable across seasons. Document targets by variety and growth stage.

Corrective actions and retesting

Common fixes include raising lights to widen the beam, adding diffusion film, or reducing spacing between fixtures. For uneven edges, add side reflectors or extend coverage beyond the crop boundary. If hotspots persist, dim slightly and increase distribution. After adjustments, retest using the same grid and record the new uniformity score. Small changes compound into reliable, repeatable production. Save exports to build a lighting maintenance record.

FAQs

1) What grid size should I use for a bench or bed?

Use a grid that captures edges and center. Start with 3×3 for small trays, 4×4 or 5×5 for benches, and increase points when CV is high or fixtures overlap irregularly.

2) How often should I test light uniformity?

Test after installing lights, after any height or spacing change, and at least seasonally. Recheck whenever plants look uneven, you replace drivers, or you clean lenses and reflectors.

3) Can I mix lux and PPFD readings in one calculation?

No. Use one unit type per test so ratios remain meaningful. If you must compare devices, run separate tests and focus on uniformity ratios, which are unitless, rather than absolute intensity.

4) What is a good uniformity score for plant growth?

Many growers aim for Min/Avg around 0.70 or higher. Sensitive crops may need better. Use your crop response as the final judge, and track the same metric over time for consistent comparisons.

5) Why choose Min/Avg instead of Min/Max?

Min/Avg highlights the weakest zone relative to typical conditions, which often predicts plant stretch and delay. Min/Max is stricter and can be dominated by one hotspot. Use the method that matches your goal.

6) What if I don’t have a PPFD meter?

You can still map uniformity with lux or foot‑candles if readings are consistent. Keep sensor height and grid spacing fixed. For crop‑specific targets, borrow or rent a PPFD meter to calibrate intensity once.