Flash Mode: Red-Eye Reduction
Everyone who has used a camera has experienced some of their photos being cursed with red eye. Fortunately, there is a flash mode designed to make red eye a problem of the past.
Using Red-Eye Reduction
Red eye is caused by the light on a camera's flash. The light enters the subject's pupil, gets reflected by the retina and is bounced back at the camera causing the eyes to appear red. Red eye reduction works by emitting a small pre-flash before the main flash. The pre-flash causes the pupils to contract and this reduces the amount of light entering the eye, which thus reduces the red eye.
One of the disadvantages of red eye reduction is that it takes a little effort to find it in most camera menus. Most times, a flash is used because you want to get the shot quickly, instead of taking your time to find the right ISO and exposure balance. Because it is not easily accessible, most people choose not to use it because they're more concerned with capturing the moment instead of getting the perfect shot.