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ayan asked in Consumer ElectronicsCameras · 1 decade ago

What is the reason for red eye effect in flash digital images?

Give me the biological reason ?

11 Answers

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  • Bill G
    Lv 6
    1 decade ago
    Favorite Answer

    Lots of correct answers here. The cause is that the angle between the flash, the retina and the lens is too narrow. I like to bounce the flash off the ceiling or attach a cord to it and hold it away from the camera when I take the shot. The red is just the flash being retruned from the retina. You are seeing the blood vessels. Neat. Try it with a dog and the retina is green.

    Sorry. Gave you a biological reason and a physics reason. My bad.

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  • Anonymous
    1 decade ago

    "Red eye" is not just a problem with digital photography. It's also a problem with film and for the same reason. The "red eye" is the reflection of the flash's light on the retina.

    "Red eye" is visible to the sensor/film when the line of sight for the flash and the lense are close to being in the same plane. By moving the flash either up or to the side, the "red eye" becomes invisible; invisible because the reflection of light is still there but the reflection is obscured by the front of the inside of the eye.

    Moving the flash up is the preferred direction, because the shadow of the subject will be obsured by the subject. Moving the flash to the side will create a distinct shadow on the opposite side of the subject.

    That's why the onboard flash on many SLR cameras is actually on fairly long arms. The arms get the flash well up over the lens when deployed.

    Many devices have been sold over the years to eliminate this problem, but the best of the best is the Stroboframe. It solves the problem in both landscape and portrait modes. Flash manufacturers have incorporated swivel heads to help also. You can turn the flash to the side or bounce it off a ceiling, etc. But the Stroboframe is still the best solution.

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  • Thomas
    Lv 4
    4 years ago

    It happens when your flash is too close to your lens. This causes the light from the flash to bounce off a person's retinas at just the right angle that it can be seen in the picture. Human retinas reflect back the color red. To solve the problem, use the preflash (causes pupils to constrict, blocking the flash), use software to color the red something else, have the person look somewhere else besides directly into the camera or simply mount a flash on the camera's hotshoe, which is usually well away from the lens.

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  • 1 decade ago

    Hello =)

    It is the same reason for red-eye in non-digital images....

    The flash is too close to the lens of the camera...

    The human retina reflects red...(you may have noticed that deer in your headlights reflect green)....same basic principle...

    If you could move the flash further from the axis of the eye-to-lens, it wouldn't happen.....

    The other alternative is to have your subjects look away from the lens.....which is why old photographers used to say "watch the birdie" and hold up a bird slightly off-axis.....

    Give it a whirl, and see what you think...

    Source(s): Retired camera-store owner.....
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  • 1 decade ago

    the pigmentation on peoples eyes are different, so some people are more prone to red eye than others. In a nutshell....the iris of your eye opens and contracts when you go from outdoor daylight, indoors where it is not so bright, the pupil of the eye OPENS UP, then when someone comes along (indoors) with their camera and flash...the pupils of the eye are in a vunerable position (wide open) and until that first photo with FLASH is taken....THEN the iris of the eye starts to close down after the first FLASH, and any subsequent shots usually have less red eye than the first shot. The red you see is actually the blood corpussels!

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  • Anonymous
    1 decade ago

    When the person you are taking the photo of is looking directly at the camera, the flash reflects off the back of their eye and strait back to the camera. The easiest way to avoid this is to not use a flash. You could try asking people to look at something else and not directly at the camera. Merry Christmas.

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  • 1 decade ago

    It's the light reflecting off the back of the eye.

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  • 1 decade ago

    The light is reflecting off of the retina, which is red

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  • Anonymous
    6 years ago

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