Everyone's had a photo that makes their eyes appear bright red. What is the cause of red eye, and what are some of the ways ...

Most of these slave flash units are triggered when they see a bright light, or when the on-camera flash goes off. Point and shoot models usually have a ‘pre-flash’ that cause a slave flash to ...

Rather, it occurs when someone is exposed to bright light, says Dr. Benjamin S. Bleier, a sinus specialist at Mass Eye and Ear. Sunlight is the most common culprit, but even a camera flash can set ...