Why animals eyes glow in the dark, but human eyes appear red in the picture

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When we see in photographs or films about the nature of animal eyes in the headlights, we see that those eyes shine brightly, reflecting the light. But human eyes in the photos, it happens otblёskivayut red. What caused this glow?

Glitter red human eyes can be compared with the brilliance of the moon. It is the light that came from the other, larger source and then reflected eyes. The flash chamber passes through the pupil and reaches the back of the eye - the retina. The retina, in turn, reflects the light back to the camera, but it does it very peculiar. As our other internal body, the retina is a very unsightly chaos of the blood vessels. They are the reason that the light reflected from the retina, it turns red. We literally paint the light of their own blood.

But what about the animals' eyes? After all, dogs, cats and deer also have blood, but their eyes on the photos do not look like the eyes of a vampire. Their eyes shine in the dark because of the special layer, which is located behind the retina of their eyes. This layer is called the «tapetum lucidum» (lat. Tapetum - veil). And it reflects the light directed into the eye of an animal, because it is - it is what it is for. Cats, dogs, deer and other nocturnal animals have a good night vision because the light is caught in their eyes, immediately reaches this particular layer behind the retina, almost without affecting photoreceptors. The light is then reflected from a particular layer, again passes through the eye of the animal. In this way, the animals receive more photons from the object that they are considering.

The reflectivity tapetum lucidum layer is much higher than the reflectivity of the retina. Redness in the eyes of the animals is not observed because the color red is replaced with a substance that makes up the reflective layer. Although the pigments of the retina and pupil also affect the color of the lights, but this effect is very small, and most of the light reflected from the eye of the animal, goes back almost unchanged. It is because of the lack of a special layer of the eye in humans may look red. And they look only at the photographs and not in the glow of the lantern. At the low reflectivity of the retina, and it can shine only during very strong and short flashes. Flash camera gives a huge amount of light, and this light is directed someone's face. Some cameras can remove "red eye", making two flashes for a very short period of time. During the first outbreak, our pupil reflex is compressed and does not let in too much light eyes, which can then be reflected by the retina and because of which our eyes on the photo will look like in the eyes of a vampire.

via factroom.ru

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