WEBVTT - BrainStuff Classics: What Causes Red Eye in Photos?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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<v Speaker 1>I'm Lauren vogel Bam, and today's episode is another brain

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<v Speaker 1>Stuff classic. What causes red eye in photos and how

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<v Speaker 1>can you prevent it? Our former host, Christian Sager has

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<v Speaker 1>the answers for you High brain Stuff. I'm Christian Sager,

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<v Speaker 1>and I'm here to talk to you about why people's

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<v Speaker 1>eyes sometimes appear red in photos. Horrible glowing red, the

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<v Speaker 1>glow of eyes that have peered into the abyss and

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<v Speaker 1>through which the abyss peers back. I'm just kidding. It's

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<v Speaker 1>it's just simply a reflection. Everything that you can see

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<v Speaker 1>is reflecting some amount of light. You can see my

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<v Speaker 1>shirt because it's reflecting wavelengths of light and absorbing the

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<v Speaker 1>other wavelengths. Black things like my soul or I guess

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<v Speaker 1>my pupils absorbed most of the light that hits them.

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<v Speaker 1>Most pupils look black because they're shadowy windows to the retina.

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<v Speaker 1>The retina is lined with a dark pigment melanin, to

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<v Speaker 1>promote light absorption that gives all the photosensitive cells in

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<v Speaker 1>the retina the best chance at catching the light coming

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<v Speaker 1>at them. The retina contains a lot of those photosensitive cells,

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<v Speaker 1>some one hundred and seven million of them, plus nerves

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<v Speaker 1>to carry messages from those cells back to the brain.

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<v Speaker 1>All that stuff needs blood to function, so the retina

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<v Speaker 1>is also dense with blood vessels. Red eye is just

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<v Speaker 1>a glimpse at those blood vessels. You see. Camera flashes

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<v Speaker 1>illuminate everything within their reach, including the blood vessels in

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<v Speaker 1>the retina. A camera with a built in flash will

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<v Speaker 1>have that flash pointed directly at the subject at the

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<v Speaker 1>speed of light. The flash bounces off the subject and

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<v Speaker 1>back to the lens. If the angle is just right,

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<v Speaker 1>you wind up looking like a minion of zul. Part

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<v Speaker 1>of the problem is that you're using a flash, you're

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<v Speaker 1>in dim light, meaning that you're sub objects. Irises will

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<v Speaker 1>be dilated with lots of retina showing. Traditional built in

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<v Speaker 1>flashes go off near simultaneously with the shutter way too

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<v Speaker 1>fast for your iris is to contract. That's why some

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<v Speaker 1>newer flashes go off twice, once right before the picture

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<v Speaker 1>snaps to make your eyes adjust, and then again to

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<v Speaker 1>illuminate the scene. You can also prevent red eye by

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<v Speaker 1>controlling the angle of the light. Use a separate flash

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<v Speaker 1>positioned a few feet away from the camera. And try

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<v Speaker 1>bouncing the light off a nearby surface instead of pointing

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<v Speaker 1>it directly at your subject. Today's episode was produced by

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<v Speaker 1>Tyler Clang and written by Me in the Way Back

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<v Speaker 1>for our YouTube series If you miss Christian you can

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<v Speaker 1>find him on his new pop culture podcast super Context.

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<v Speaker 1>And if you enjoy our show and want to support

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<v Speaker 1>us in return for some brainy house wears or people wears,

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<v Speaker 1>visit our online shop at te public dot com slash

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<v Speaker 1>brain staff. And of course, for more on this and

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<v Speaker 1>a lot of other bloody excellent topics, visit our home planet,

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<v Speaker 1>how stuff Works dot com. H