This odd-eyed cat displays<unk>  of its tapetum lucidum only in its blue<unk>  In flash photography the light of the flash occurs too fast for the pupil to close, so much of the very bright light from the flash passes into the<unk>  through the pupil, reflects off the fundus at the back of the<unk> ball and out through the pupil. The camera records this reflected light. The main cause of the<unk>  color is the ample amount of blood in the choroid which nourishes the back of the<unk>  and is behind the retina. The blood in the retinal circulation is far less than in the choroid, and plays virtually no role. The<unk>  contains several photostable pigments that all absorb in the short wavelength region, and hence contribute somewhat to the<unk> . The lens cuts off deep blue and violet light, below 430 nm (depending on age), and macular pigment absorbs between 400 and 500 nm, but this pigment is located exclusively in the tiny fovea. Melanin, located in the retinal pigment epithelium (RPE) and the choroid, shows a gradually increasing absorption towards the short wavelengths. But blood is the main determinant of the<unk>  color, because it is completely transparent at long wavelengths and abruptly starts absorbing at 600 nm. The amount of<unk>  light emerging from the pupil depends on the amount of melanin in the layers behind the retina. This amount varies strongly between individuals. Light-skinned people with blue<unk> s have relatively low melanin in the fundus and thus show a much stronger<unk>  than dark-skinned people with brown<unk> s.<unk>  on dark brown<unk> s Intense<unk>  in blue<unk> s with dilated pupil The same holds for animals. The color of the iris itself is of virtually no importance for the<unk> . This is obvious because the<unk>  is most apparent when photographing dark-adapted subjects, hence with fully dilated pupils. Photographs taken with infrared light through night vision devices always show very bright pupils because, in the dark, the pupils are fully dilated and the infrared light is not absorbed by any ocular pigment. The role of melanin in<unk>  is demonstrated in animals with heterochromia: only the blue<unk>  displays the effect. The effect is still more pronounced in humans and animals with albinism. All forms of albinism involve abnormal production and/or deposition of melanin.<unk>  is seen in photographs of children also because children's<unk> s have more rapid dark adaptation: in low light a child's pupils enlarge sooner, and an enlarged pupil accentuates the<unk> . Theatrical followspot operators, positioned nearly coincidentally with a very bright light and somewhat distant from the actors, occasionally witness<unk> -eye in actors on stage. The effect is not visible to the rest of the audience because it is reliant on the very small angle between the followspot operator and the light.
Red-eye effect
Stroop effect
Mandelbaum effect
Windkessel effect
Baskerville effect
Eagle effect
Bowditch effect
Tissue selectivity