You may have encountered the red eye option in every photo editing software and sometime you too have encounter these magical red eyes in yours photos, if not, go and click a photo in dark. So, what actually are these red eyes?
The blame for this go to the bright flash of camera, and how your eyes adapts to changes in light. Your eyes are basically fluid filled orbs that can detect light and sense messages to your brain, so you can see images. Light passes through a thin membrane called cornea, then a hole called the pupil, and then a lens so it can be focused and absorbed by photoreceptor cells in the back of your eyes. Your pupil filled by this muscles filled structures called the iris, which is the colored part of your eye. You don’t consciously move these muscles, but they control how big your pupil is, and how much light can in.
When it’s dark your iris make the pupil wider to let more light into your eyes and when it’s bright your pupil get contracted. So, the Red Eye Effect usually happens in a dark environment when your eyes are widen enough. Normally, all the light that enters your eye is absorbed by photoreceptors, or by a pigment called Melanin in a tissue layer in the back of your eyes-the same pigment that influences the color of your skin, hair and iris. And since your eyes absorb all colors, make pupils look black. But if there is sudden a bright camera flash and all that light floods into your eyes, before your eyes have time to contract. Some of it might reflect off the blood vessels in back of your eyes, making it glow up.
So, how to fix them? To fix such problem, there are camera with multiple flash i.e. before glowing actual flash, they glow demo flash which help your eyes to adjust. You can also skip from red eye effect, either by not directly focusing on camera or by shifting the focus of light to nearby object.
