A person uses a camera and takes a photo...and the flash wasn't off. The resulting flash either blinds the unfortunate recipient of said photo or makes them see spots. This can be used as a handy distraction or even as a nasty form of Improvised Weapon. Truth in Television as anyone who's ever had to take a school photo or have been at an area with a lot of flash photography can attest. Sub-Trope of Blinded by the Light.
Hello, Unknown Troper. You'll need to get known to lend a hand here.