Inside Photoshop® CS

The Dreaded Red-Eye

We've all seen it. You snap a photo of a friend or relative, and the results look like something out of a horror movie. What causes red-eye? The basic fact is that the pupils naturally respond to light exposure by expanding in low-light levels and contracting in high-light levels. If you're in a low-light environment, the pupils expand to a large size, and when a flash goes off, the light travels through the dilated pupil and reflects off the blood vessels behind the retina. This reflection is translated back to the camera in the form of a distracting red spot.

You can use certain photographic techniques and equipment to reduce the possibility of red-eye in an image. Some of these measures are as follows:

• Turn on the lights ...