Ask David: Why Do I still Get Red Eye in Night Shots? :: Digital Photo Secrets

Ask David: Why Do I still Get Red Eye in Night Shots?

by David Peterson 1 comment

This question comes from reader Rick Bergesio. He’s tried the red eye flash setting on his camera, and it hasn’t done much to reduce red eye in his night shots. If the system isn’t working as advertised, then what’s going on? Why do his photos still have problems with red eye?


Top Photo: Tim Regan

The red eye flash is a good tool to help reduce red eye problems, but it isn’t a get out of jail free card. Before I can tell you why, we need to look into the science of red eye.

What causes red eye?

Whenever you shine a flash on the eye, some portion of that light gets reflected off of the retina, back toward the camera. Red eye is the result of excessive amounts of light reflecting directly off the retina. Have a look at the photo above. Notice how only the back of the pupil is red. The more light that is directly shined at the eyes, the worse the red eye.

But there is another factor in the equation, and that is the pupil. Your pupil contracts and expands to control the amount of light that makes it to your eyes. It is a similar thing as aperture in your camera, except it’s the one built into your eyes. If you’re in a very dark room, your pupils expand. When you’re out in bright sunlight, they contract.

So here’s the situation that causes red eye:

  • Your subjects are in a dark room
  • You are shining a bright light directly at them (or use your camera's inbuilt flash).

Because the room is dark, their pupils are wide open and therefore more receptive to the light. When the picture is taken, the entire retina is reflected back because nothing is stopping the light from getting to the back of the eye.

How does red eye flash solve the problem?

The red eye flash was developed to solve this problem in a kind of clever way. If you are using your red eye flash properly, you should see two flashes. The first flash is like a flicker, and the second flash comes in a little more strongly to take the actual picture.

The flicker is where the secret lies. It’s designed to force your subjects to contract their pupils, thus allowing less light into their eyes for the actual picture. This reduces the appearance of red eye, but depending on your shooting conditions, it might not eliminate the problem altogether. The pupils contract some amount, but they don’t contract all the way. If it’s dark enough, some of the light from the flash will still get reflected back.

How to get rid of red eye when red eye flash doesn’t work

First, make sure your red eye flash is working. If you don’t see the flicker before the flash, your camera might not have a genuine red eye flash mode. It might just be a gimmick that attempts to remove red eye with software.

Next, turn up all of the lights in the room. The more available light you have, the more your subjects’ pupils will contract, allowing in less light. Of course, you’ll only want to do this as much as the situation permits. If it’s not an appropriate time to do so, don’t turn someone’s house upside down just to get a few pictures.

Aside from turning up the lights, there isn’t much else you can do without purchasing an external flash for your camera. Red eye happens because the flash on your camera sits on top of the lens. It shines light directly at your subjects’ eyes, and the light gets reflected right back into the lens.

The only sure-fire way to beat red eye is to disconnect the flash unit from the camera and illuminate your subjects from the sides. When you do this, the light is no longer aimed straight at your subjects’ eyes, so it doesn’t reflect back with nearly the same intensity. You can also bounce the flash off the walls, reducing its intensity that way.

I wish there were an easier way to get rid of this fairly common problem. It’s unfortunate that camera makers overpromise and underdeliver when it comes to features, but that’s a fact of life in the photography world. I hope some of these techniques work for you.

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Comments

  1. Roelof van Heerden says:

    Good day
    Yes red eye is a problem with digitals. We newer had red eye with the film even when the flash is a built-in on the camera. I suppose it has to do with the sensitivity of the sensor (semicondutors react differently) more than where the flash actually is positioned. Maybe one of our readers can help here with the scientific reason?
    Something els, I would like to know why one needs more that even 5 focus points to work with? My firs SLR was a Zeiss Cataflex and later a Cotarex, which I stil have, and there I had only a split-image, which was enough. I only use the one focus point om my 7D and that is the midpoint. If I want somting to be in focus on the side, then it is quite easy to just focus there and than lock that area and re-position my camera.
    Thank you
    Roelof van Heerden

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