Photography: How to Avoid Red-Eye in Flash Photos

Photography: How to Avoid Red-Eye in Flash Photos

What is red-eye, and why does it happen?
We’ve all seen it in snapshots we’ve either taken ourselves, or been shown by others: the pupils of your subject’s eyes are lit up in a devilish bright red color, unlike anything we’re used to seeing in real life. And of course, you never saw it in your camera’s viewfinder when you took the picture.

What is happening is that the pupil of a person’s eye, even though it appears to be black when we view it, is actually clear. Since the inside of the eyeball is normally never illuminated, we see it as a small black circle. But in some flash photos, if the flash is close to the lens of the camera, its illumination sends a burst of light right through to the rear of the inside of the subject’s eyeball. The retina of your subject’s eyes is rich in red blood vessels, and this produces the bright red color we see in the pictures.

If the flash is close enough to the lens, the light not only enters your subject’s inner eye, but can then reflect straight back out and actually be recorded by the camera. With the retina in your subject’s eye now fully illuminated, you get the tell-tale bright red glow that we all now know as "red-eye." So the first thing to know is that for all intents and purposes, red-eye in photos is a flash phenomenon. It’s very unlikely you’ll encounter it using sunlight, or available light only when shooting indoors.

Using the built-in flash:
Cameras like the Canon EOS Digital Rebel XT and XTi have a built-in flash, that pops upwards an inch or two for easy and convenient flash photography – at least, as long as your subjects are not too far away. And nearly every compact digital camera has a built-in flash as well. Since many of these cameras are so small in size, the designers are often forced to put the built-in flash nearly right next to the lens. Any time you use a built-in flash that’s close to the lens, you run the risk of occasionally getting red-eye in any pictures with people in the scene.

Obviously, you can’t physically move the built-in flash away from the camera lens. So manufacturers have resorted to another feature: Red-Eye Reduction.

Red-eye Reduction:
The idea of this feature is that by one means or another, the camera sends out light to your subject before the picture is taken. Since the subject’s pupils normally tend to dilate, or get wider, in dim light (and get smaller in bright light conditions), the idea is to reduce the level of red-eye by making the user’s pupils appear smaller before the picture is taken. With smaller pupils, there’s less area to be marred by red-eye, and even if it does show up in your pictures, it’ll tend to be less noticeable.

Some cameras do this by rapidly flashing the flash unit with "pulses" of flash illumination, for a second or two before the picture is taken. The hope is that your subject’s eyes will react to these rapid pops of light and the pupils will become smaller. A moment later, that actual picture is taken, with the flash firing again, but at (usually) greater power.

Canon’s cameras take a different approach, using a small, built-in lamp to shine continous white light directly at your subject for about two seconds, prior to the picture being taken. In fact, a scale appears on EOS digital SLRs with this feature in the viewfinder, to count down the two seconds that this red-eye reduction lamp is active, so that you know when to fully press the shutter button and take the picture. Again, the idea is that this added light before the picture is taken will cause the subject’s pupils to contract, and therefore reduce the level of red-eye if it appears.

It’s important to understand that neither of these approaches to in-camera red-eye control ever claim to completely eliminate the chance of getting visible red-eye. As the feature’s name says, it’s red-eye reduction, not red-eye elimination.

Using accessory speedlites:
Since an accessory flash unit (like Canon’s Speedlite 430EX, or 580EX) is larger and sits on top of the camera, the flash unit itself is raised several inches above the lens. The flash-emitting part of these units is nowhere near as close to the lens as in the case of a built-in flash. This distance between lens and flash means that right from the start, you’re less likely to get red-eye in your pictures. Let’s be clear: we’re not saying you won’t or can’t get red-eye in pictures taken with an accessory flash unit, only that because it starts out being a few inches farther from the lens, you can often avoid the probem in your shots of people.

Distance plays a key role in red-eye:
It’s a fact that the farther you are from a subject, the more likely you are to get red-eye in your flash pictures of people. The farther away you are from a subject, the more the flash illumination tends to be parallel to a straight line entering your camera lens. If flash illumination can go straight into your subject’s pupils, and then reflect straight back out again, you’ll see it as red-eye in your pictures. But if instead it’s at a slight angle relative to the "axis" that the lens is seeing, you’ll usually avoid that direct kick-back of light into the camera, and the subject’s pupils will usually appear the normal black color.

So to avoid red-eye, try to do the following:

1. Where possible, try to step physically closer to your subjects. This doesn’t mean be only inches away, but if you have a choice of taking that birthday party shot from 15 feet away, with your zoom lens at a telephoto setting, or stepping to about 6 feet away with the lens at a wider-angle setting, you’re much less likely to get red-eye from the 6 foot distance.

2. Try to resist using telephoto zoom settings in flash pictures of people. It’s not that telephoto lenses have anything to do directly with red-eye – they don’t – but any tele lens encourages you to stand back at a greater distance from your subject(s). It’s this added distance that increases the chances of red-eye.

Other techniques to avoid red-eye:

1. Bounce flash
If you’re using an accessory speedlite with bounce capability, and if you’re shooting indoors in a room with relatively low, light-colored ceilings, you can tilt your flash head upward so it shines at the ceiling, and then “bounces” back down to your actual subject(s). If done properly, this will totally eliminate any possibility of red-eye appearing in your flash pictures. The reason is that the flash illumination actually striking your subject is now coming downward, from the ceiling.

Remember that your ceiling must be white or near-white (if it’s colored, the returning light hitting your subject will take on that color – it’s no fun to eliminate red-eye, only to have an entirely red subject from that red-painted ceiling). And the other thing is that you need a standard ceiling height – somewhere around 8 to 12 feet. Bounce flash obviously won’t work in the open outdoors, and you can’t expect it to work in a large ballroom, or in a high-school gym. Finally, you’ll need to experiment and practice somewhat to get the hang of how far upward to tilt your flash head, depending upon how far away you are from your subjects (unlike direct flash, with bounce, you’re actually better off taking a step or two away from your subject, to get your light coming down at an angle instead of from directly above).

2. Use a third-party flash bracket
You’ve no doubt seen this one at every wedding you’ve been to: the pro photographer who’s shooting the wedding has his or her flash mounted on a contraption that holds it way, way above the camera. It looks totally awkward, but the pro using it has a point: by moving the flash well above the lens and its optical axis, he or she has much less concern that red-eye will appear in their flash photos. These brackets come in styles that “rotate” or “flip”, as well as completely rigid types. The rotating brackets let you position the flash head above the lens, regardless of whether you’re shooting horizontal or vertical pictures. With the rigid types, your flash may be positioned way off to one side if you turn the camera to take a vertical picture.

Canon doesn’t market these brackets, but many third-party companies do, in a wide variety of styles, degrees of ruggedness, and price points. Well-stocked camera stores usually have them on-hand. And to retain your E-TTL flash, use Canon’s Off Camera Shoe Cord 2, with one end attached to your camera’s hot shoe, and the other attached to your bracket’s flash shoe. Now, the flash will be as automatic as if it was directly on top of the camera.

3. Take the flash off the camera
Using either the Off Camera Shoe Cord 2, or Canon’s wireless E-TTL flash system, remove your flash entirely from the camera and position it elsewhere. By moving it off-camera, you virtually eliminate any possibility of red-eye. Using either the Speedlite 430EX, or the 580EX in their “slave” mode, and triggering them with an optional Speedlite Transmitter ST-E2, it’s easy to get fully automatic flash exposure, with the flash up to 20 feet or more away from the camera. The ST-E2, combined with one of these speedlites, is a great combination for effective bounce flash shooting as well, whether you’re holding a single flash off-camera in one hand, or using multiple flash units to evenly light a room or area.

4. Use available light, and don’t shoot with flash
In some conditions indoors, or at night, you can get beautiful, natural-looking pictures by simply turning off your flash, setting a higher ISO, and using natural light to take pictures. Try this along with flash pictures in different scenes, and you’ll develop a sense of when to revert to this technique. It certainly eliminates any chance of seeing red-eye.

Source: Canon