Do you have red eyes? Or are they blue, brown or hazel? Of course, regardless of what color eyes you have, you may look like you have red eyes in photographs from time to time.

Have you ever had your picture taken and noticed afterward that you look like an alien or a zombie with bright, glowing red eyes? This is called the “red eye effect.” Although it looks magical and somewhat sinister, there’s a reasonable scientific explanation for it.

So what causes your blue (or brown or hazel) eyes to turn red in certain photographs? The red eye effect happens when flash pictures are taken in low-light situations. When the flash is located close to the camera lens (as it is in most cameras), you may be looking almost directly at the flash when you look at the camera lens.

The red eye effect results when the light of the flash occurs too quickly for the pupil of the eye to close. The bright light of the flash passes into the eye through the pupil, reflects off the retina at the back of the eyeball and returns back out through the pupil. The camera records this reflected light, and it appears red because of the amount of blood located in the back of the eyeball.

The red eye effect tends to be stronger in people with light eye colors, light hair colors and fair complexions. Scientists believe this is because these people have less melanin in their eyes, which helps to reduce the red eye effect to some extent in people with darker eyes, hair colors and complexions.

If you have pets, you may have noticed that the red eye effect can be quite different in animals. Animals have a special reflective layer at the back of their eyes called the tapetum. The tapetum helps to enhance night vision. Depending upon the animal, the tapetum can cause a blue, green, or yellow eye effect.

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    • We’re not sure about that one, Evan! We’ll have to do some more WONDERing! Because the sunlight is constant, and not a “quick” flash like that from a camera, it would be interesting to find out if the special “tapetum” that animals have in their eyes causes a strange effect in just bright sunlight! Thanks for thinking more about this Wonder after you were done exploring it! :-)

  1. We just love taking pictures!! :) We like to post our pictures on Facebook to share with our friends. We also talked about things we do with our pictures such as keep them in photo boxes, picture frames around our house, or even scrapbooking…. We liked having tips for getting rid of red-eyes. One of our teachers said her camera flashes twice as part of its red-eye reduction option.

    • Happy Friday, Kerrick Elementary School! We’re so glad you talked about ways you can share pictures, and we’re glad you shared your awesome comment with us! Thank you for visiting today’s Wonder! :-)

  2. I have hazel eyes, but they can get very light because my mom has light blue eyes. I only get the red-eye effect when I take a picture on a day when my eye color is fairly light. Does that make a difference? My sister gets red-eye effect way more than me and she has Dark Brown eyes. Why does that happen? Thank you!!

    • That’s very interesting, Autumn! Even though the “red-eye effect” is supposed to be lesser in people with darker eyes and complexions, it all depends on the person! There are exceptions to some rules, and maybe your eyes and your sister’s eye are just extra awesome! Thanks so much for your comment today! :-)

    • We think it was cool to learn what causes them in pictures, though, didn’t you, ASD? Thanks so much for leaving us this comment today and for letting us know what you think about red eyes! :-)

  3. Wow, wonderopolis! I never really took the time to wonder about this, and I always thought that this whole red-eye was a technology problem. Who knew your eyes could turn red? Thanks and keep wondering!

    • Hello, Nitnik! We’re so glad you stopped by Wonderopolis today and left us this great comment! Thanks for letting us know that you learned something new from this Wonder about the red-eye effect! We’ll keep WONDERing every day if you will, too, OK? :-)

  4. Hey there, Wonderopolis crew! I think that red eyes are interesting to learn about. But, then again, almost everything on here is fun to learn about! If you took a picture of a person who has white eyes would the red eye affect affect them? Thanks!

    • Hello, Abby! It’s GREAT to hear from you again! That’s a really smart question about the eyes. We’re not sure what would happen, as we’ve never seen anyone with a complete lack of pigmentation in their eyes. Let’s do some more WONDERing about that, OK? :-)

    • Hi, Blake! If you’ve got red eyes when you look in the mirror, it might mean you’re sad (and you’ve been crying), you have allergies, or you haven’t had enough sleep, and NONE of those sound like fun to us! Red eyes in photographs aren’t really “bad,” but lots of Wonder Friends wish they didn’t show up when they look at their pictures! :-)

  5. I liked learning about red eyes. I learned a lot. By the way,how do you come up with all these wonders? From Charlie, Ryne, Anaya, and Serean.

    • Thanks so much for leaving us a comment to let us know you visited this Wonder of the Day® today, Charlie, Ryne, Anaya and Serean!

      Did you know that this Wonder was actually the idea of a Wonder Friend just like YOU? It’s true! One of our AWESOME Wonder Friends let us know what they WONDERed about by clicking on the “nominate” link that’s found at the top of every page in Wonderoplis and answering a few easy questions! It’s FUN to nominate ideas for future Wonders…we hope you’ll give it a try, too! :-):-)

  6. I don’t get why a red eye is bad…..
    I had a red eye in a picture before, but I wasn’t sad or feeling bad.
    Plus, I have no allergies.

    • That’s a great point, Moa! Some Wonder Friends might not be upset when their eyes appear red in photographs. We just WONDERed why that effect happens, so we thought it would be a FUN idea for a Wonder of the Day®! Thanks so much for sharing your comment with us…we appreciate you! :-)

    • Thanks for your comment, Ria! We’re super excited that you and your dad are going to Wonder together– keep up the great work! We Wonder if you have an idea for a website of your own already?! :)

    • Hi Grim, yes, many animals are born with red eyes. Sometimes the colors of their eyes change, but often they remain red, especially if they’re albino. Thanks for WONDERing with us today! :)

    • Hmmm, we’re not sure why your eyes appeared both blue and red at the same time, Anthony! We hope you’ll do some extra digging on the Internet or in your library to find the reason! :)

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Have you ever wondered…

  • Where do red eyes come from?
  • What causes the red-eye effect?
  • How can you prevent red eyes in photographs?

Wonder Gallery

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Try It Out

Did today’s Wonder of the Day make you see red? Grab a friend or family member and explore one or more of the following activities to keep the learning going!

  • Do you know all the parts of your eye? Jump online and check out this neat Eye Diagram interactive. Did you have any idea your eyes were made up of so many different parts? Isn’t it amazing how all the parts work together to help you see the world around you?
  • Say cheese! Get out the family camera and take a few pictures with your friends and loved ones. As time passes, you’ll never regret having lots of pictures to record the fun times. What do you do with all of the pictures you take? Do you keep them in photo albums? With the popularity of digital photographs, you may keep them in online photo albums or post them to popular social networking sites, such as Facebook. Here are a few fun ideas for crafty photo albums you might want to try:

Get a friend or family member to help you with one of these projects. There’s nothing more fun than reminiscing as you work on a craft project together. Have fun and enjoy your time together!

  • Up for a challenge? Learn how to take better photographs and reduce the red eye effect! Read through these helpful tips and then try them at home:
    • Turn on more lights and avoid using the camera’s flash, if possible.
    • Use an external flash with your camera, so that the flash is farther away from the camera lens.
    • Use the red eye reduction feature, if your camera has it. This feature uses the flash repeatedly before taking the picture, so that the pupil has time to contract.
    • Have your subject look away from the camera lens.
    • Use graphics editing computer software to remove the red eye effect digitally after the photograph is taken.

What do you think? Did they work? Share your photographs with friends and family members. Tell them what you did to make your photographs turn out so awesome!

Still Wondering

Check out National Geographic Xpeditions’ Tell a Migration Story…with Photos activity to learn how you can use pictures to tell the story of your community’s cultural heritage.


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