Eye shine in nocturnal mammals is different from the red eye seen in some flash photographs.eye shine is the reflection of light off the tapetum lucidum.what visual mechanism might explain red eye ?

The red-eye effect in flash photography is different from the eye shine seen in nocturnal mammals. The red-eye effect occurs when the flash of a camera shines light into a person's eyes and the camera captures the light reflecting off the back of the retina. Here's how it happens:

1. A camera flash emits a bright light that travels into the subject's eyes almost at the same time as the camera's shutter opens. 2. The pupils of the subject might not have enough time to constrict because of the sudden intense light, and thus they often remain relatively dilated. 3. The light from the flash passes through the pupil and reaches the fundus at the back of the eyeball, where the retina is located. 4. The retina contains a rich layer of blood vessels and appears red because of the blood, which is rich in hemoglobin. This is particularly noticeable in photography because the blood vessels can reflect a substantial amount of the flash's light back out through the pupils. 5. The camera captures this reflected light, and the photograph thus exhibits the well-known red-eye effect, where the pupils look brightly red.

Eye shine, on the other hand, is a phenomenon seen mostly in nocturnal animals. Their eyes have a specialized layer called the tapetum lucidum that reflects visible light that passes through the retina back into the environment. This increases the amount of light available to the photoreceptors of their eyes, enhancing their night vision.

Extra: The tapetum lucidum is a layer of tissue located behind the retina that reflects visible light back through the retina, increasing the light available to the photoreceptors. This adaptation is beneficial for nocturnal animals as it improves their ability to see in low light conditions. In many animals, the reflected light produces a noticeable glow that can be different colors like green, yellow, blue, or white, depending on the specific composition of the tapetum lucidum and other factors.

In contrast, the human eye lacks a tapetum lucidum, which is why we do not see eye shine in humans and why the red-eye effect is more relative to the physical structure (retina and blood vessels) and our camera technology rather than an evolved trait aimed at enhancing low-light vision like in nocturnal mammals. Reducing the red-eye effect in photography can be accomplished by using red-eye reduction features on cameras, which typically involve pre-flashes that cause the subject's pupils to constrict, reducing the amount of light that can be reflected out.