Problem
A lighting technician tests fixtures individually but misses beat-frequency interaction when two different PWM fixtures illuminate the same face.
Solution
Root Cause / Diagnostic:
When two LED fixtures operating at slightly different PWM frequencies (e.g., 2,000 Hz and 2,005 Hz) illuminate the same surface, their waveforms beat together. This optical interference creates a low-frequency rolling beat that neither fixture exhibits when tested alone.
Actionable Fix:
1. Standardize all fixtures on set to identical brands and models sharing synchronized PWM driver frequencies.
2. Power fixtures from the same master distribution dimmer or set all fixtures to 100% output to eliminate PWM modulation.
3. Test all set lights activated simultaneously on the camera waveform monitor; confirm zero slow-frequency exposure beating.
Pro Tip:
Always perform camera flicker testing with 100% of the lighting cues turned on together to catch inter-fixture beat frequencies.
When two LED fixtures operating at slightly different PWM frequencies (e.g., 2,000 Hz and 2,005 Hz) illuminate the same surface, their waveforms beat together. This optical interference creates a low-frequency rolling beat that neither fixture exhibits when tested alone.
Actionable Fix:
1. Standardize all fixtures on set to identical brands and models sharing synchronized PWM driver frequencies.
2. Power fixtures from the same master distribution dimmer or set all fixtures to 100% output to eliminate PWM modulation.
3. Test all set lights activated simultaneously on the camera waveform monitor; confirm zero slow-frequency exposure beating.
Pro Tip:
Always perform camera flicker testing with 100% of the lighting cues turned on together to catch inter-fixture beat frequencies.