Causes of and avoiding red eye in photos

I’m sure this has been asked before, so initial apologises for repetition (but can’t search for 3 letter words)

What causes red eye in photographs?
Are certain people or eye colours more subject to it than others?

Just got holidays snaps back and every photo of me has me with glaring red eyes, whereas everyone else is normal.
Can I stop this from happening in future, (or is the camera really seeing my true demonic soul?) :wink:

Is it a matter of how you look at the camera or some inherent physical characteristic?


Red eye is the reflection of the flash off the red-tinted blood vessels at the back of the eyeball. If the light from the flash enters and exits directly through the iris back to the camera lens, you get red eye. The people who did not get red eye were not looking directly at the camera, so the flash was not reflected back to the camera lens. You do not have to lok very far away from the camera; you can still face it for your photo, just look over the photographer’s shoulder or something.

Avoiding red eye.

Eh, it’s the reflection of the flash from your retina I believe, and it can be fixed by using a camera that has a redeye eliminator or by getting Kodak to do post operative surgery, or, don’t use the camera in situations where you need the flash!

The flash causes red eye. You know how if you shine a light in a cat’s eyes’ the pupils glimmer due to the light bouncing around in there? Well, the same thing happens in humans and the red in the pupils of a photograph is how that reflected light comes out in film. Eye color matters not, everyone is subject to it equally.

It’s a matter of how you are looking at the camera and the light conditions. If you are in a dark room, your pupils are more likely to be dilated so the light from the flash reflects and escapes more easily than if they were undilated.

The best way to prevent it is to close your eyes in every picture.

Although it can be difficult to implement simply with inexpensive cameras, a good solution to redeye is to illuminate the subject indirectly by reflection off a white screen out of the field of view. Illuminating for several seconds before exposure will also reduce redeye, by causing your subjects to have smaller pupils. (This tactic may produce undesirable results, in some cases.)


I always thought it was because of absorption of part of the flash light by rhodopsin - reflecting red.

If a pre flash is used is ‘uses up’ the rhodopsin - converts it from trans to cis configuration (or is it the other way around).

Just don’t use the flash. The on-camera flash is the worst photographic invention ever - it creates a very flat lighting and causes red eye. If the room is reasonably well lit, you will get much better results without the flash. You will be more prone to camera shake, however, so you need to learn how to hold the camera staedy. (Tuck the elbow against your chest, hold the camera firmly and only move your finger to push the shutter.) It may also help to use a faster film. Modern ISO 800 films are pretty good.

If that isn’t an option, you might try looking at a bright light just before a photo is taken of you. This will close down the pupil a little bit. You could also try looking slightly away from the camera.

By the way, the reason that nocturnal animals have a greenish tinge to the eye - like when you go spotlighting roo’s - is due to a reflective film behind the retina, the tapetum, which is ‘designed’ to reflect back more photons onto the retina, and thus improve night vision.

Also further expanding on previous post, rhodopsin is the chemical in the rods in the retina that is integral to the conversion of photons to an electrical impulse - it’s change in confirmation is the first in a chain of steps that creates the signal.

Do a search on rhodopsin.

Are you sure it is not because this ‘bleaches’ the rhodopsin? Wouldnt a closed down pupil just give you a smaller red eye?

Thanks for the quick and concise answers.

All the indoors photos (with flash) have me with red eyes.
But…in most of the photos taken outside (on snow) I still have the red eye look and no one else does.

So, can a lot of reflected light cause red eye even if there is no flash?

No I’m not sure, I wrote that post before I saw yours. Most explanations I’ve read (e.g. here) say that the red color is the color of the retina, and that closing down the pupil helps.

By the way, you could try to touch it up later. Some photo editing software have special tools for touching up red eye. They even make red eye reduction pens. (I think it’s just a green felt tip pen, but maybe normal ones damage photo prints.)

The “special pens” I’ve used will damage the photo, too, if you over do it.

Professionals use flash units which are mounted away from the axis of the lens, either quite high above or to the side. That way the light is not reflected straight back towards the lens. They also tend to use diffusers fitted over the flash.

It’s not entirely independent of the person’s physical attributes. From Kodak:

What color are your eyes, Aro?

My eyes are generally blue (sometimes a little green.) They seem to change occasionally. Maybe that explains why I am more susceptible to red eye than my friends with their common-as-muck brown eyes.

(The photos were all taken with a crappy Kodak Fun camera, BTW.)

People with darker eyes have less of a tendency to exhibit red-eye; one theory as to why it took camera manufacturers so long to come up with the ‘pre-flash’ concept is that the (dark-eyed) Japanese never saw it as a problem.

On a point and shoot camera eliminating red-eye is near impossible.

The red eye has nothing to do with rhodopsin being used up at all. As most people have correctly pointed out, it’s a reflection off the back of the retina, which in humans is typically about a salmon color.

I use this effect all the time in my office for various tests. For testing if pupils are the same size (or measuring them) I’ll use an instrument called a ophthalmoscope, typically used to look at the retina, from about two feet away. At that distance, I get a beautiful red reflex from both eyes that doesn’t fade even after a minute or two, and even with pretty low levels of light. Turn it up, and the reflected light drops dramatically as the pupil shrinks.

OK Eirik, you sound like you are in a good position to know this.

I stand corrected.

I take photos of animals more than people, but here is something interesting, pertaining to cats:

A cheap and simple red-eye reducer (not eliminator) is, if I remember correctly, to tape or rubber-band a piece of toilet paper over the flash. It’ll difuse the light, so there’ll be fewer direct reflections straight back into the lens, but won’t make the flash ineffective.