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Why are there red-eye

Why is there a red eye

The photographs of people taken in low light with flash, red-eye often seen.

This effect arises because the light from the flash reflects off the retina of the eye.

The device's eyes and the flash

In many animals, including dogs, cats, deer, lining the retina is covered with a special layer. It's called "mirror" because it has reflective properties.
If the night to shine into the eyes of animals, youYou see how they shine their greenish or white light. This is because the pupil of the eye is extended in the dark. Since the pupil passes light that falls on the back wall of the eyeball and is reflected from the retina. Thanks to this device, animal eyes see well in the dark. Mirror collects light, and the animal's eye as light illuminates objects in the gloom.
In humans, unlike animals, have lining layer on the rear wall of the eye. If in the dark shine man in the eye, then no reflection will not be visible.
But the camera flash light is bright enough toIn order to get a reflection. What you see in the pictures - the blood vessels that nourish the eyeball and the retina. The choroid of human eyes is very thick. Since the blood vessels are red, then from the retina reflects red light rays and sent back through the pupil. During the picture, everything happens so fast that the pupil does not have time to shrink, miss a lot of light, and the picture is visible inside the eye side.
Human eyes are different in structure. In some people, the pupils are dilated a little more than others. Then their eyes appear more red. There are people with a high content of melanin in the skin. The eyeball of the pigment layer will absorb some of the light that eliminates red-eye.

How to avoid the red-eye effect

Many cameras have a specialdevice against the red-eye. The flash is activated twice in them. For the first time - before the image. At this time, the bright light the pupil narrows. The second time the flash is activated during image.
To avoid red eye in the picture, you can turn on all the lights in the room. It also narrows the pupil.
When the pupil is narrow, it misses much less light into the eye. Thus, light is reflected from the inner side of the eyeball.
Before you take a picture, some photographers first few times the flash is activated, so that the pupils of people who are narrowed.
Another way to get rid of red eye inPhotos - take the flash as far away from the camera lens. The little camera flash is just a few centimeters from the lens. Reflection on the retina of the eye is directed straight at the lens. From this red-eye effect becomes more noticeable.
If the flash is removable, in order to avoid uglyimage can take her as far away from the lens. If it is possible to set the flash so that it can bounce off the walls and ceiling, then this method will work much better.

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