How many times have you taken some photographs only to find that the people in them have glowing red eyes? If you were like me, it's probably been often. What used to confuse me was that it sometimes happened, and it sometimes didn't. Why does this thing called "Red-eye" happen. To answer this we have to first take a closer look at the eye itself. The eye is a marvelous piece of engineering (I'm a Creationist, even Darwin couldn't explain how eyes could develop by random chance). I will try to explain the eye in simple terms, although it is very complex. The eye is shaped like a ball, filled with clear liquid. At the front is a lens that refracts (bends) light so it falls into focus at the back of the eye. In front of the lens is the iris, which is a diaphram that controls the amount of light that enters the eye. It's opening gets smaller in brighter light to allow less light into the eye. At the back of the eye is the retina, a mass of light-sensitive nerves that actually "capture" the image the eye sees and send it to the brain for interpretation. Behind the retina is a reflective layer that bounces light that passes through the retina back again. Light that enters the eye either hits the retina or is reflected off the back of the eye; which has a second chance to hit the retina. Thus any light that enters the eye has two chances to strike the retina and produce and image. It's almost like taking the net off a hockey goal. Now the puck would have two chances to go through the goal. If someone made a shot and missed, it just might bounce off the boards behind the goal and go through the net in the opposite direction. This reflective layer helps out a great deal in low-light situations. This feature is greatly enhanced in some animals, such as cat's, which have excellent night vision. When you see a person's eye glowing in a picture, you are actually seeing the light reflected off the back of their eye. Why is it red? Because the retina is red. A person's pupil is normally black because there is no light inside the eye, and thus it is black. It would be like cutting a small hole into the side of a closed box. The hole would appear dark because it's dark inside the box. However suppose you would put a piece of aluminum foil or a mirror inside the box opposite the hole. If you would shine a flashlight at the hole from the outside, the light would bounce off the reflective surface and come back out the hole, causing it to glow. This is what is happening when you see people's eyes glowing in pictures. There are 3 ways to reduce or eliminate "red-eye" from photographs. The first way is to move the electronic flash farther from the camera lens. When the light is reflected off the back of the eye, it exits the eye in a cone shape. The smallest part of the cone is at the eye, and it becomes larger the farther from the eye it gets. Imagine putting a hole in one side of a closed box and putting a light in it. If you would point the hole at a wall, it would produce a circle of light. If you move the box away from the wall, the circle of light would become bigger. The farther away from the wall you move the box, the bigger the circle of light would become. Now, combine this information with the fact that light is reflected BACK TO IT'S SOURCE. So the light from electronic flash is reflected BACK to the electronic flash (in a cone that gets bigger the farther from the eye that you get). If you have a camera with an electronic flash that is built into the camera body, when the light is reflected back to the flash, it also hits the lens, and you get red-eye. If you have a hotshoe, you can put an electronic flash on the top of your camera. By doing that, you put more distance between the flash and the camera lens. When the light is reflected toward the flash, the lens has more of a chance to be out of the cone of light because it is farther away from the flash. The second way to reduce or eliminate red-eye is closely related to the first. Try to move closer to your subject. Since the light that is reflected from the eye is cone shaped, the closer you move to your subject, the smaller the cone is. The light reflected back towards the flash may hit the flash only at 6 feet. But at 20 feet, the cone of light would have expanded to not only hit the flash, but the camera lens as well, causing red-eye. The third way to reduce red-eye is to raise the level of light in the room by turning on more lights. By doing this, the iris of the eye closes into a smaller hole. Since the eye is now admitting less light into the eye because of the additional light, it will also let less light from the flash into the eye, and also less light to reflect off the back of the eye. To sum it all up, to reduce, or hopefully eliminate red-eye: 1) Move your flash farther from your camera lens. 2) Move closer to your subject. 3) Raise the level of natural light. An alternative way, when all else fails, is to remove red-eye from the pictures themselves. If you use a fine felt-tip pen (permanent works best) you can just cover over the red irises to make them black. You should practice on prints that you do not care about until you become good enough to trust your skill on prints that you do care about.
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