Photography tips: Avoid red-eye: the red eye effect, is due to reflection of the flash light on the retina that are widely dilated. Above is given for people with sensitive eyes. To avoid it is desirable to have good lighting in the place where it is to take the shot or perform the "red eye" which is built into most cameras on the market. This way of using flash is conducting a series of flashes prior to the execution of the photo to contract the pupil and prevent red eye.