Red eye. Nothing can turn an adorable child into evil demon spawn more effectively than red eye, unless you count four hours playing Minecraft or a can of Pepsi and a candy bar. Red eye is that thing that haunts all hobby photographers’ photo albums, especially the albums full of photos that your mom shot with her little Instamatic camera (“just wait for the flash to warm up, honey!”) There was a time when we accepted red eye as something that just happens, an unhappy side effect to taking pictures indoors in low light. But thanks to modern technology and a little bit of knowhow, it may please you to hear that red eye is not, in fact, an inevitable fact of flash photography.
The Red Eye Setting is Bullshit by Flickr user Richard Guthnur
Fixing Red Eye Video
Watch a video for extra tips on Fixing Red Eye
But first – what causes Red Eye?
I’m kind of a sciency guy, so I have to admit to having a little bit of morbid fascination about what red eye is and why it happens. As it turns out it’s a quite interesting and entirely explainable phenomena that has almost nothing to do with the supernatural. I’ll bet you’re relived.
Red eye happens when the light from your flash reflects off of the retina at the back of your subject’s eyes. The reason why it’s associated with flash is because flash is sudden—in a normal lighting situation your pupils will constrict when the light gets brighter, which allows less light in and lets you see normally without squinting. But when someone introduces a sudden, bright flash of light, your eyes don’t have time to react. Your pupils remain wide (which is why you also tend to make painful exclamations right afterwards) and the flash sort of takes over the whole eye. The light reaches your retina, which is full of blood vessels, and when it reflects back it takes on the lovely blood-red color of the retina.
Now the angle of the light has a lot to do with this, too, which is why you’ll tend to notice red eye happening a lot more often when you use your onboard flash. The reason why it’s so much more of a problem for built-in flashes (vs. off-camera flashes) is because your built-in flash has a direct line of sight to your subject’s eye. In other words, the light is aimed directly at that retina right behind those wide-open pupils. When your subject is looking at the camera you’re more likely to get red eye, too, again because of that whole direct line of sight problem.
So what can you do about red eye? Well the good news is that there are a lot of really effective strategies. The first one is becoming standard on modern cameras and is the one you’ll probably look to first when you try solving this problem.
“Red eye Reduction” is a pre-flash that’s designed to reduce the impact of the main flash. It’s usually symbolized by an eye icon such as the one below. When you turn it on, your camera will send out a small flash just before the main one—that small flash isn’t enough to illuminate the scene but it’s enough to cause your subject’s eyes to constrict the way they would if they were outdoors or in a bright room. Then, when the main flash goes off your subject’s eyes will be constricted instead of dilated, which will allow less light to reach the retina, which will in turn lessen or eliminate the red eye.
Make sure to check your LCD often to see if the red-eye reduction tool (whether you’re using the built in feature or you’re bouncing/diffusing your flash) is giving you the results you want. Your results can vary a lot depending on the angle of the light and where your subject was looking during the pre-flash. If you didn’t get good results, make some adjustments and try again. Remember that you can also ask your subject to look away from the camera or you can elevate your external flash so that light isn’t going straight into the eyes.
Now, one of the drawbacks to using your camera’s red-eye reduction mode is that it adds time on to the process. When you use red-eye reduction, there is a delay between the time you press the shutter button and the time the camera actually takes the photo. How much of a delay depends on your camera model—the Nikon N70, for example, has a lag of about one second, which is the amount of time that the red-eye reduction lamp shines before the main flash fires and the shutter releases.
Add to that the fact that you have to locate and engage the red eye reduction feature in your camera’s menu, you may actually lose some photo opportunities.
So let's say that you don't want to bother with redeye reduction, or you have a camera that doesn't have that feature. You shot the photo anyway, and now you have those bright red demon eyes in all your photos. Are you stuck? Will you be forced to populate your family photo album with pictures of little demons and devils? Happily, the answer is “no.” Provided you have some basic knowledge of post processing software, you can correct redeye after the fact.
Most modern post processing packages have red-eye reduction built right into the toolset. If your package has this tool, correcting redeye is really just a matter of selecting the eye and engaging the tool. If your software doesn't have that capability, it's still going to be pretty easy to fix red eye by simply selecting the red area of the eye and desaturating it. Then, adjust the levels in the selected area to get a natural looking black tone in the pupil.
If you don’t have a post-processing package, you can download a free program such as Picasa, which offers many of the same tools as a popular pay-package like Elements or Lightroom. Picasa handles red-eye removal just as well as the paid programs do.
How to remove red eyes, the harder way ;) by Flickr user Yannig Van de Wouwer
But really, the best way to avoid red eye is to just avoid situations that cause it. Red eye happens when you use direct flash, so it follows that you can avoid red eye by simply avoiding the use of direct flash. The very best way to do this is by replacing your popup flash with an external flash. Most external flashes are designed with a pivoting head, which means that you can point it at a wall or ceiling or other large white surface and bounce your flash instead of aiming it directly at your subject. The benefits of doing this is that the light scatters, which means that it's not going directly into that dilated pupil.
You can get the same basic effect by diffusing the light, which is a useful technique if you don’t have an external flash unit. Simply place something white and semi-transparent over the flash (such as a piece of white paper or tissue) ad that will also help to scatter the light.
The take away from all of this, of course, is not that you should avoid your flash, or that you should avoid shooting in low light. The take away is that you should be aware of why and when redeye is going to be a problem, and then take the proper steps to avoid it. When your mom was filling up that childhood photograph album with her flash-lit Instamatic photos, she probably didn't pay much attention to all the red eye apart from its commenting on how funny it made everyone look. But you know better than that. Understanding red eye and learning how to avoid or fix it is a very useful tool in any photographer’s arsenal.