The red is light reflecting off the inside of the eye from the harsh direct light from a flash mounted close to the digital camera lens. In dim light, where you are more likely to need a flash, the pupils in the eye open wider to let in more light and accentuate the red eye effect. Depending on your camera and flash some, or all, of the following strategies will help to reduce this effect in your portraits.
Move the Flash
Moving the flash away from the digital camera lens is the basis of professional portrait photographer’s strategies for combating red eye. Pro shooters use a variety of flash set ups, ranging from a single external flashgun to a complex collection of units with a master flashgun, and a number of slave units that fire under control of the master.
Spread the Light
This is another technique for avoiding harsh direct light from the flashgun by placing a diffuser in front of the flashgun. By spreading the light, the diffuser reduces the direct light from the flash entering the eyes and consequently the reflections straight back to the camera lens. There is a wide variety of aftermarket devices to help diffuse the light from digital cameras with built in flash.
Bounce the Light
Instead of pointing the flash directly at the subject, another way to spread the light is to bounce it off a nearby surface. Favorites are white ceilings or a neighboring wall, and this is why they make flashguns with moveable heads. Professionals use portable reflecting panels for situations where there is not a suitable reflecting surface. While some reflectors are flat panels, one common device is the umbrella. The light from an external flashgun bounces off the curved underside of the photographic umbrella giving a nice soft diffused light.
Red Eye Reduction Flash
This is common with on camera flash systems and aims to reduce the size of the red eye spot by making the eye’s pupil smaller. Firing an early burst from the flashgun makes the eye react to the bright light and contract the pupil. This reduces the amount of light going into the eye and the size of any visible red spot in the eye. After this first burst of flash, the flashgun fires again while the camera’s shutter is open.
Software Tools
Most photo editing software packages offer an automated red eye tool. This tool replaces the red pixels in the eye with black pixels, and the eyes now look normal. One of the example photos shows the original image after using a software red eye tool.
 |
 |
 |
