The distinct eyeshine given off by various animals originates from the tapetum lucidum, which are mirror like cells behind or in the retina. Some light getting into the eye is captured in the retina, while some goes through. The light is then bounced back at the retina by the tapetum lucidum and this enables the animal to see during the night. This reflecting light is the one that gives off the indistinctly frightening glow, whereas the green color is caused by the substance in the animal’s tapetum. There is a normal amount of pigment in the retina that affects the colour. However, the age of the animal and other factors can affect the colour; hence two dogs that belong to a similar species can have eyes giving off different colours. Cats mostly are the one whose eyes are bright green during the night (Seabrook, 2008).
The human eye appears red in colour in flash pictures because the flash of the camera bounces off the red tissues and the blood vessel behind the eyes. This occurs as a result of the photographic flash is used very closely to the camera lens in ambient little light. Nevertheless, the cause of red eye is found in both animals and individuals whose eyes lack tapetum lucidum (Surtenich, 2013). The effect of the red eye is as a result of fundus colour that is due to melanin, which is a pigment mainly located in the retinal pigment epithelium. Since the flash of the camera occurs very quickly for the pupil to close, a lot of light gets into the eyes, which is then reflected back by the fundus situated behind the eye. This reflected red light gets caught up and recorded by the camera (Jones, 2013).
References
Jones, L. (2013). Speedlights & Speedlites: Creative Flash Photography at the Speed of Light. United States: Taylor & Francis.
Seabrook, A. (2008). Why do animals’ eyes glow in the dark.
Surtenich, A. (2013). Why eyes look red in photos and how to prevent and fix red-eye.