Red eye is a common problem in pictures that are taken with flash. But not all of the flashes necessarily create the red eye effect, mostly camera-top flashes or built-in (pop-up) flashes are the ones that create red eye effect. Because they are too close to lens and in the same axis with lens, light coming from these flashes hits the eye directly which increases the risk of having red eyes in the picture.

How to Prevent Red Eye

• Turn the head of flash to a white wall or ceiling so flash light can bounce all over the room and create much more balanced light in the room. This is not an option for built in pop-up flashes, their direction can not be changed, unfortunately.
• Place the flash to a different position if you can, not on the same axis with the lens.
• Taking pictures without flash is the best option in my opinion. If there is not enough light in the room, you can use an ambient light for lighting the room. If you are in a situation that you cannot find a light to increase the amount of light in the room, reduce the exposure 1 or 2 stops and than increase it in raw picture processing softwares or photoshop.
• In modern SLR cameras there’s red-eye reduction option so you can use it.
• If you have a built-in pop-up flash and if you have to use it, tell the subject he or she should not look to the camera directly, instead he/she should look shoulder of the photographer.
• Also if you have red eye problem in the picture you can remove it by using softwares such as photoshop.