2006-06-13 16:53:42 · 9 answers · asked by Tasso 1 in Social Science ➔ Sociology
The light of the flash occurs too fast for the iris of the eye to close the pupil. The flash light is focused by the lens of the eye onto the blood-rich retina at the back of the eye and the image of the illuminated retina is again focused by the lens of the eye back to the camera resulting in a red appearance of the eye on the photo. (This principle is used in the ophthalmoscope, a device designed to examine the retina.)
The effect is generally more pronounced in people with grey or blue eyes and in children. This is because pale irises have less melanin in them and so allow more light to pass through to the retina. Children, despite superficial appearances, do not have larger pupils but their pupils are more reactive to light and are able to open to the fullest extent in low light conditions. Many adults have lost the ability to fully open their pupils except through the use of drugs.
In many species the tapetum lucidum, a light-reflecting layer behind the retina that improves night vision, intensifies this effect. This leads to variations in the colour of the reflected light from species to species. Cats, for example, display blue, yellow, pink, or green eyes in flash photographs
2006-06-13 16:57:02 · answer #1 · answered by Stuart 7 · 1⤊ 0⤋
Why do people have red eyes in flash photographs?
the answer to this question is:We've all see photographs where the people in the picture have spooky red eyes. These are photos taken at night with a flash. Where do the red eyes come from?
The red color comes from light that reflects off of the retinas in our eyes. In many animals, including dogs, cats and deer, the retina has a special reflective layer called the tapetum lucidum that acts almost like a mirror at the backs of their eyes. If you shine a flashlight or headlights into their eyes at night, their eyes shine back with bright, white light. Here is what Encyclopedia Britannica has to say about the tapetum lucidum:
Among many nocturnal vertebrates the white compound guanine is found in the epithelium or retina of the eye. This provides a mirrorlike surface, the tapetum lucidum, which reflects light outward and thereby allows a second chance for its absorption by visual pigments at very low light intensities. Tapeta lucida produce the familiar eyeshine of nocturnal animals.
Humans don't have this tapetum lucidum layer in their retinas. If you shine a flashlight in a person's eyes at night, you don't see any sort of reflection. The flash on a camera is bright enough, however, to cause a reflection off of the retina -- what you see is the red color from the blood vessels nourishing the eye.
Many cameras have a "red eye reduction" feature. In these cameras, the flash goes off twice -- once right before the picture is taken, and then again to actually take the picture. The first flash causes people's pupils to contract, reducing "red eye" significantly. Another trick is to turn on all the lights in the room, which also contracts the pupil.
Another way to reduce or eliminate "red eye" in pictures is to move the flash away from the lens. On most small cameras, the flash is only an inch or two away from the lens, so the reflection comes right back into the lens and shows up on the film. If you can detach the flash and hold it several feet away from the lens, that helps a lot. You can also try bouncing the flash off the ceiling if that is an option.
2006-06-14 23:42:43 · answer #2 · answered by nan.sweety 3 · 0⤊ 0⤋
It's to do with the retina in your eye. When you need a flash your retina is open and the flash going off is reflected as red. Most camera's these days have a red eye reducing flash, 1 flash to close your retina a little then the other to lighten the picture.
2006-06-13 23:59:55 · answer #3 · answered by darkness_returns 4 · 0⤊ 0⤋
If I'm not mistaken, it is because the flash enters the eyeball through the pupil and illuminates it...the red color is from the blood vessels inside the eyeball that are now visible from the added intense burst of light.
2006-06-13 23:57:36 · answer #4 · answered by dharma bum 1 · 0⤊ 0⤋
it's a reflection off of the retina. to solve the problem, preclick the flash once to make the pupil smaller (or stare into a light bulb.
2006-06-13 23:55:48 · answer #5 · answered by Christine in FL 1 · 0⤊ 0⤋
it is the light from the flashing bouncing back off the eye because the eye is not ready for it... it happens more in light colored eyes...
2006-06-13 23:57:11 · answer #6 · answered by curious 2 · 0⤊ 0⤋
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2014-09-13 21:55:05 · answer #7 · answered by ? 3 · 0⤊ 0⤋
It just happens
2006-06-13 23:57:08 · answer #8 · answered by Judas Rabbi 7 · 0⤊ 0⤋
IT'S BECAUSE OF REFLECTION ON YOUR EYES
2006-06-14 05:02:24 · answer #9 · answered by sj2011 1 · 0⤊ 0⤋