When it comes to having your picture taken, it's all about the eyes. While blinking can ruin an otherwise great picture, so can red eye: that awful thing that makes your pupils glow red and look demonic.
Red eye in pictures is such a common occurrence that nearly every digital camera and smartphone has a tool to get rid of it. But if we understand what causes that freaky red glare, we can prevent it from happening in the first place.
For the most part, it has to do with the camera flash.
As SciShow explains, our pupils regulate the amount of light we let into our eyes. When it's bright, the pupils become smaller. They become larger when it's dark, letting as much light in as possible. The problem is that the camera's flash doesn't give our eyes enough time to adjust to the light, snapping the picture while the pupils are still dilated.
So how does that make our eyes look red in pictures?
Watch the video and find out:
Cover image: Shutterstock