Problem
A dimmer-controlled tungsten practical pulses during its AC waveform, becoming visible after shooting at a high frame rate.
Solution
Root Cause / Diagnostic:
Tungsten lamp filaments heat and cool with the cyclical rise and fall of the 50/60 Hz AC power sine wave. At standard frame rates the filament thermal inertia masks this fluctuation, but high-frame-rate shooting exposes the 100/120 Hz thermal pulsing.
Actionable Fix:
1. Power tungsten lamps using specialized high-capacity DC power rectifiers or regulated DC battery packs.
2. Swap low-wattage bulbs for high-wattage heavy-filament bulbs (2kW+) whose thicker filaments retain heat and resist rapid thermal decay.
3. Review slow-motion test clips at 120+ fps; verify steady luminance without cyclic dimming cycles.
Pro Tip:
Heavier tungsten bulbs (2,000W and above) have massive filament mass that holds temperature across AC cycles, making them naturally flicker-free for slow motion.
Tungsten lamp filaments heat and cool with the cyclical rise and fall of the 50/60 Hz AC power sine wave. At standard frame rates the filament thermal inertia masks this fluctuation, but high-frame-rate shooting exposes the 100/120 Hz thermal pulsing.
Actionable Fix:
1. Power tungsten lamps using specialized high-capacity DC power rectifiers or regulated DC battery packs.
2. Swap low-wattage bulbs for high-wattage heavy-filament bulbs (2kW+) whose thicker filaments retain heat and resist rapid thermal decay.
3. Review slow-motion test clips at 120+ fps; verify steady luminance without cyclic dimming cycles.
Pro Tip:
Heavier tungsten bulbs (2,000W and above) have massive filament mass that holds temperature across AC cycles, making them naturally flicker-free for slow motion.