Red-eye is an optical effect caused by the light from a camera flash. The flash lights up so quickly that the pupil of the eye doesn't have time to contract. The light bounces off the retinal blood vessels inside the human eye, making the eye look unnaturally red. Since most people don't enjoy looking like an enraged vampire, you should try to prevent red-eye either while taking photos or while editing them.
The most obvious thing you can do is to avoid shooting your subject head on with a flash. Try shooting from an angle, where the flash won't directly impact the eye. The next step is to enabled the red-eye reduction mode that comes with most digital cameras today. With red-eye reduction, the camera automatically recognizes lighting conditions that cause red-eye and triggers several brief preflashes before the main flash. This allows the pupils to contract so red-eye never occurs.
Of course digital camera red-eye reduction modes do not always work flawlessly, so you may need to remove the offending problem after the fact. All major photo-editing applications let you remove red eye, and these features are pretty easy to use.
Step By Step: Fixing Red-Eye
1. In Flickr for example, open the offending photo and enable the Picnik photo-editing tools. Zoom and pan to the red-eye affected area.
2. Click the Red-Eye tool. Choose whether you're editing a Human or Furball (animal) and click the center of each red eye.
3. Red turns to black and your photo subject has returned from the undead.
This story, "How to Get Rid of Red Eye" was originally published by PCWorld.