Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,
Speaker 1: I'm Lauren vogel Bam, and today's episode is another brain
Speaker 1: Stuff classic. What causes red eye in photos and how
Speaker 1: can you prevent it? Our former host, Christian Sager has
Speaker 1: the answers for you High brain Stuff. I'm Christian Sager,
Speaker 1: and I'm here to talk to you about why people's
Speaker 1: eyes sometimes appear red in photos. Horrible glowing red, the
Speaker 1: glow of eyes that have peered into the abyss and
Speaker 1: through which the abyss peers back. I'm just kidding. It's
Speaker 1: it's just simply a reflection. Everything that you can see
Speaker 1: is reflecting some amount of light. You can see my
Speaker 1: shirt because it's reflecting wavelengths of light and absorbing the
Speaker 1: other wavelengths. Black things like my soul or I guess
Speaker 1: my pupils absorbed most of the light that hits them.
Speaker 1: Most pupils look black because they're shadowy windows to the retina.
Speaker 1: The retina is lined with a dark pigment melanin, to
Speaker 1: promote light absorption that gives all the photosensitive cells in
Speaker 1: the retina the best chance at catching the light coming
Speaker 1: at them. The retina contains a lot of those photosensitive cells,
Speaker 1: some one hundred and seven million of them, plus nerves
Speaker 1: to carry messages from those cells back to the brain.
Speaker 1: All that stuff needs blood to function, so the retina
Speaker 1: is also dense with blood vessels. Red eye is just
Speaker 1: a glimpse at those blood vessels. You see. Camera flashes
Speaker 1: illuminate everything within their reach, including the blood vessels in
Speaker 1: the retina. A camera with a built in flash will
Speaker 1: have that flash pointed directly at the subject at the
Speaker 1: speed of light. The flash bounces off the subject and
Speaker 1: back to the lens. If the angle is just right,
Speaker 1: you wind up looking like a minion of zul. Part
Speaker 1: of the problem is that you're using a flash, you're
Speaker 1: in dim light, meaning that you're sub objects. Irises will
Speaker 1: be dilated with lots of retina showing. Traditional built in
Speaker 1: flashes go off near simultaneously with the shutter way too
Speaker 1: fast for your iris is to contract. That's why some
Speaker 1: newer flashes go off twice, once right before the picture
Speaker 1: snaps to make your eyes adjust, and then again to
Speaker 1: illuminate the scene. You can also prevent red eye by
Speaker 1: controlling the angle of the light. Use a separate flash
Speaker 1: positioned a few feet away from the camera. And try
Speaker 1: bouncing the light off a nearby surface instead of pointing
Speaker 1: it directly at your subject. Today's episode was produced by
Speaker 1: Tyler Clang and written by Me in the Way Back
Speaker 1: for our YouTube series If you miss Christian you can
Speaker 1: find him on his new pop culture podcast super Context.
Speaker 1: And if you enjoy our show and want to support
Speaker 1: us in return for some brainy house wears or people wears,
Speaker 1: visit our online shop at te public dot com slash
Speaker 1: brain staff. And of course, for more on this and
Speaker 1: a lot of other bloody excellent topics, visit our home planet,
Speaker 1: how stuff Works dot com. H