What Causes Red Eye In Photos?


(classical music) – Hi I’m Jonathan, and I’m
here to talk to you about why peoples eyes sometimes
appear red in photos. Horrible, glowing red. (thunder) The glow of eyes that
have peered into the abyss and through which the abyss peers back. Naw, I’m just kidding,
it’s a simple reflection. Everything that you can see is reflecting some amount of light. You can see my shirt because it’s reflecting blue wavelengths of light and absorbing the other wavelengths. Black things like my my
Lav mic or my pupils, absorb most of the light that hits them. Most pupils look black because they’re shadowy windows to the retina. The retina is lined with
the dark pigment melanin to promote light absorption. That gives all the photosensitive
cells in the retina the best chance at catching
the light coming at them. The retina contains a lot of
those photosensitive cells, some 107,000,000 of them. Plus nerves to carry messages from those cells back to the brain. All that stuff needs blood to function. So the retina is also
dense with blood vessels. Red eye is just a glimpse
at those blood vessels. You see, camera flashes illuminate everything within their reach. At the speed of light the flash bounces off the subject and back to the lens. If the angle is just right you wind up looking like hell spawn. (camera clicks) Part of the problem is that
if you’re using a flash you’re in dim light, meaning
that your subject’s irises will be dilated with
lots of retina showing. Traditional built in flashes go off near simultaneously with the shutter. Way too fast for your irises to contract. That’s why some newer
flashes go off twice. Once right before the picture snaps to make your eyes adjust, huh, and then again to illuminate the scene. You can also prevent red eye by controlling the angle of the light. Use a separate flash positioned a few feet away from the camera and try bouncing the
light off a nearby surface instead of pointing it
directly at your subject. Do you have any reflections on red eye? See what I did there? Let me know in the comments. You can learn about why
your pet’s eyes glow other colors in Josh and Lauren’s video, which is hovering somewhere over here. If you like this video, make it official, and subscribe so you
won’t miss the next one. And for lots more stuff for your brain check out brainstuffshow.com.

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