An Introduction to Red Eye

What Causes Red Eye?

Red eye occurs when the light from a camera’s flash bounces off the subject’s retinas and reflects back into the camera lens. Because the visible part of the human retina contains mostly blood-rich tissue, the reflection makes the subject’s pupils look red in photographs. The red eye effect also occurs in photos of animals, but often the reflected color is green, yellow, or another color other than red, depending on the particular animal. Note that Photoshop’s Red Eye tool (which this guide covers in detail) works only on red eyes.

 

When Does Red Eye Occur?

• When shooting in low light: In low light, the pupils dilate (enlarge) to let in more light. A fully dilated pupil lets more light bounce off the retina, which in turn leads to larger, more pronounced red eye effects.
• When shooting with a built-in flash: Red eye is worse in cameras in which the flash is located very close to the lens. In these cameras, which include all point-and-shoot cameras and many digital SLRs with pop-up flashes, the light bounces right off the retina and straight back into the lens whenever the flash is fired. Photos taken with external flashes, which are mounted on top of the camera, have fewer red eye problems because the light from the flash enters the eye at an angle and therefore doesn’t bounce straight back into the lens.

How to Fix Red Eye

• Don’t use the flash: Red eye occurs only in flash photography, so whenever possible, avoid using the flash. For instance, when shooting in a low-light situation, consider mounting your camera on a tripod and increasing your exposure time rather than using the flash. If you don’t have a tripod handy or don’t want to use one, try taking the shot with the flash turned off—usually, pressing the button with the flash icon (a lightning bolt) on the camera body will toggle among your camera’s available flash modes.
• Use an external flash: If you shoot frequently in situations that require a flash, such as at parties, consider buying a camera that can accommodate an external flash. Some higher-end point-and-shoot cameras, such as the Canon Powershot G7® and the Nikon Coolpix P5000®, as well as all digital SLRs, can use external flashes.
• Use photo editing software: Red eye is an easy problem to fix with many photo editing software packages. Most photo editing programs contain a specific feature dedicated to removing red eye with just a few clicks, such as Photoshop’s Red Eye tool. Though it’s better just to try to avoid red eye in the first place, these software tools can help rescue photos otherwise ruined by red eyes.