Every smart-glass conversation eventually lands on the same question: how good is the privacy, really? This is the engineer's answer — what PDLC actually blocks, what it leaks, and what to pair it with for true zero-visibility privacy. What "privacy" means for PDLC glass When PDLC film is unpowered (opaque state), it scatters light rather than blocking it. From arm's length you see a uniform white haze — no silhouettes, no colours. From 30 cm or closer with a strong backlight, you can just barely make out gross movement (someone moving from one side of the room to the other), but no detail, no facial features, no readable text. This is functionally equivalent to a heavy shower curtain or good frosted vinyl — perfectly private for bathroom, changing, and meeting use cases. Where the privacy limits actually show up Direct backlighting If someone is standing between a bright window and the smart glass in opaque state, an observer on the far side can see a soft silhouette. Solution: install the smart glass on the observer's side of the light source, or pair with a translucent blind on the window. Night-time interior lights An interior bathroom with the light on, viewed from a dark hallway, will show a warm glow through opaque PDLC. Fine for most residential contexts, not fine for a spa treatment room where guests expect zero light transfer. Very close approach Within 10 cm of the…