Red eye

What is it? What you can do to avoid it.

Suppose you are at a social gathering, taking a few pictures of your friends. Because it is night and the lights are low, you use your camera’s built-in flash. You capture someone’s attention, and the person looks right at you. Great expression! Fabulous blue eyes staring straight into your lens. “Click.” You shoot! The flash goes off. You think, “I’ve just captured a great picture.” When you view the picture on your digital camera's screen or later on your computer, or when you get your pictures back from the film lab, you say "Oh no! Those blue eyes have a bright red center." (or bright white with a black and white image.) What a let down! You’ve been red-eyed! What happened? And what can you do to prevent it?

First, you should know this is a very common problem, particularly with cameras having built-in or camera-mounted flash, where the flash unit is close to the lens.

Second, red eye is not a symptom of a flaw in your camera. The camera is actually operating properly in capturing red eye, because it is photographing what it “sees,” which is the back of the eye – the subject’s retina. In effect, you took a picture of the interior of your subject’s eyeballs. With the flash being so close to your lens, its light went through your subject’s iris, lit up the retina at the back of the eye – which is red in color due to its blood vessels – and captured that redness on film.

WHAT IS THE RETINA?

As we said, it's located inside the eyeball, at the back. It is about 1/100th of an inch thick, and it's where photo receptors that receive light and process it before sending it to the brain so that we can see, are located.

HERE ARE THE CONDITIONS UNDER WHICH YOU WILL GET RED EYE IN YOUR PICTURES:

1. Low light conditions. In low-light, eyes are open wider than normal so they can gather more light to see better.

2. Your flash unit is located too close to the lens. Its light reflects directly back through the lens to the film. It is similar to shooting a flash picture of a mirror, straight on; you will get a bright picture of your flash, reflected back at you, only in this case the "mirror" is the back of the subject's eyeball, which is red in color.

3. The subject is looking directly at the lens, like a deer caught in your vehicle's headlights. (When the subject is looking away – not directly at the camera – the light from your flash won’t be able to penetrate the iris and reach the retina.)

TIPS FOR AVOIDING RED EYE

1. Some cameras and flash units employ a special red eye-reducing flash that fires one or more relatively-weak pre-flashes with sufficient light to cause pupil constriction. Then the actual flash itself goes off when the camera's shutter opens. The amount of light reflected off the retina is diminished due to the subject's smaller iris opening, resulting in a reduced red eye picture - sometimes (but not always) not noticeable at all.

If your camera doesn't have this feature and you are not prepared to run out today and buy a sophisticated, new camera that does, here are some other tips you can try.

2. Use bounce flash. Deflect the light from your flash so it doesn't hit your subject directly. This is probably your best bet, since most flash units have a built-in bounce-flash capability (by tilting the flash head at an angle), and since bounced flash does not penetrate your subject’s eyes on the same plane as your lens.

You can usually bounce your flash off a wall or a ceiling, providing the wall or ceiling is white, has reasonable reflectance and is not too far away. You can also bounce the light off special white cards (such as the white card found on the reverse side of most 18%-reflectance gray cards). Some special materials are made just for bounce-flash, such as silver-coated cards.

Note that bounce flash will also soften shadows and broaden the area that your flash reaches, often creating a featureless image - i.e. lacking in shadow and 3D perspective.

If the area off of which you are bouncing your flash is not white, your images will pick up some of the area’s surface color, and this may or may not work well for you in getting the image you seek. Some photographers carry a rectangular section of white styrofoam, which provides an excellent surface for bounce flash.

When employing bounce flash, the flash-to-subject distance increases because the flash's light travels a greater distance to reach the subject since it is angled, and that greater distance must be taken into account in determining the aperture setting for a manual camera.

3. Place a diffuser such as tracing or tissue paper, a white handkerchief or any piece of white cloth over or in front of the flash to spread the light. A note of caution. There is a potential fire hazard with tissue paper. Keep the paper out of direct contact with the flash head itself to avoid igniting it.

Some manufacturers make small diffusion covers that fit over standard flash units. This technique makes it difficult to calculate the ƒ-stop to use when employing a manual camera, but the cover can be effective in reducing red eye. It works especially well with cameras that automatically calculate flash-exposure for you. The overall effect is one of softer, near-shadowless lighting.

4. If you're using a hot shoe-mounted flash, take the flash unit off your camera's hot shoe and hold it to one side, so that its light strikes the subject at a different angle of view than your lens is capturing. (You will need to acquire a special flash extension cable in order to do this.) Be prepared for stronger shadows across the person’s face. To reduce those shadows, combine this method with a flash diffuser, and you'll get great results.

As long as your flash is held about seven inches or more away from your lens, you shouldn't get red eye in your pictures.

Viewer, Victor A. Wheeler, recently supplied the following tip: "I use one of those flash brackets that carry the Stroboframe name. This has given me excellent results in red eye elimination, and even cuts down the shadows in back of the subject when photographed vertically. They're not that expensive, either. Mine was under $60." A flash bracket keeps the flash unit several inches away from the lens, and is very effective in reducing red eye. Thanks, Victor.

5. Have your subject look directly at a room light or, during the day, look outside at the brighter daylight until his or her pupils reduce in size. (You can also shine a flashlight in your subject’s eyes to get the same effect.) These measures eliminate spontaneity in your pictures, but will get rid of red eye provided you don’t wait too long to take your picture.

6. You can also simply turn up the room lights when you are shooting inside so that your subject's pupils reduce in size. The brighter the ambient light, the more the pupils will close down to conceal the blood-red retinas.

7. In a pinch, you can also direct your flash right at your subject and fire the test button on it before taking the final picture. The burst of light may constrict pupil size. As soon as your flash recycles (when the ready light comes on), shoot your picture while the pupils are still small.

This method is a little iffy, since you are hoping that the light from the first flash burst sufficiently reduces the size of the iris so you get your picture before it has begun to open again. Success will depend on how quickly your flash recycles.

8. Finally, you can ask your subject to look away instead of straight at the camera when you take his or her picture, thus eliminating any chance of red eye.

Your picture will not show direct eye contact, but may still be an excellent image, just different than if your subject were looking straight at the lens.

In many respects, this approach is similar to one of the solutions offered for subjects wearing eyeglasses where you do not want reflectance from the glass in your image. If the subject turns or looks away, you avoid reflection but lose straight-on eye contact.

RETOUCHING WILL FIX RED EYE

What can you do if you already have a photograph with red eye in it? You can fix it in a number of ways.

1. The quickest and least expensive method when you have red eye in a print is to retouch it with a red eye retouching pen, available from your camera dealer. (Caution: use a red eye retouching pen on the print, not the negative.)
2. A professional photo retoucher can also do the job for you.
3. You can also scan the image into a computer or download it from your digital camera, then use one of the many excellent photo manipulation programs, like Adobe PhotoShop for example, to retouch the digital image, and then print out the results.