Why this burning red effect in object's eyes? please explain.

[saurabh.d21]

Hi, I am an amateur photographer & have a Kodak digicam. just started learning about the technicalities of photography through DPS,

however, during a recent visit to a night fair when I clicked some photos of my friend standing in foreground against a dimly lit background what I see is this burning red effect in his eyes in photos whereas the background was underexposed and my friend somewhat overexposed. I was using a Nikon digicam in auto mode & did not change the ISO at all. The flash was working fine.

Though I have noticed this effect few times before as well for photos clicked inside my room under normal lighting conditions(read; under 2x40watt CFL lights).

Also should I attach the photo for more accurate analysis?

[zona5101]

This effect is "red-eye". It occurs when the flash, the lens & the the subject's eyes are near the same plane. The red is a reflection of the retna. You don't see it (or notice it) in picture taken with more ambient light because the pupil isn't wide open as it is when it is dark or dim. Most photo programs, even the most basic, have a red-eye removal feature. Many cameras with a built in flash have a red eye reduction flash mode that pre-flashes before the exposure to shut the pupil down and reduce the effect.

[kencaleno]

Here's how to cope with "red eye" in photoshop:

Double click Quick mask icon
Change masking color to green-opacity 60%
Paint mask over eyes
Click icon next to Quick mask
Select> Inverse
Image> adjustments> Desaturate
Add new adjustment layer-Levels
Move both input sliders towards the centre of the range until you are satisfied.
Layers> Flatten image

[OsmosisStudios]

Or get it right in-camera, which I know you're a HUGE fan of, Ken.

[kencaleno]

Originally Posted by OsmosisStudios

Or get it right in-camera, which I know you're a HUGE fan of, Ken.

Agreed Osmosis, But you need an alternative if you aren't able,or don't know how to get it right in camera-you need to have answers. Ken

[Saralonde]

Alternately, if you don't have Photoshop and didn't get it right in camera, try downloading a simple free editing program like Picasa. There is a very easy to use red eye fix in there.

[saurabh.d21]

Thanks Zona, as you stated clearly & what I could extract from your anwser is that red eye effect is caused when there isn't enough light or the subject (my friend, in my case) is underexposed. Am I right?

Are you saying that this effect is inevitable until settings are changed as "red is a reflection of the retina" which just goes unnoticed in proper lighting but caught in dim light (i.e. red eye is always there).

Please help me understand what is means "The flash, the lens & the the subject's eyes are near the same plane. Is it that the trajectory of the flash could be manipulated to avoid/change results.

I was wondering if you could also suggest the manual camera settings to prevent red eye effect apart from usuals like increasing the ISO or decreasing the shutter speed in case subject is steady.

@Kencaleno Thanks so much for your Photoshop guide. It looks even I could now edit these images I have already taken.

[kencaleno]

Hi,What happens is with a point and shoot camera,and dslrs with built-in flash,the flash causes the lens to capture the reflected red from the retina.if the flash is higher above the lens, or on a bracket attached to the camera,then red eye can be avoided-if this can't be done you will need to either resort to using post processing to remove red eye, or make sure your subject is not looking directly at camera. See below examples:

First shot looking directly into camera; second shot looking to the side
Ken

[OsmosisStudios]

Originally Posted by saurabh.d21

Thanks Zona, as you stated clearly & what I could extract from your anwser is that red eye effect is caused when there isn't enough light or the subject (my friend, in my case) is underexposed. Am I right?

Are you saying that this effect is inevitable until settings are changed as "red is a reflection of the retina" which just goes unnoticed in proper lighting but caught in dim light (i.e. red eye is always there).

Please help me understand what is means "The flash, the lens & the the subject's eyes are near the same plane. Is it that the trajectory of the flash could be manipulated to avoid/change results.

I was wondering if you could also suggest the manual camera settings to prevent red eye effect apart from usuals like increasing the ISO or decreasing the shutter speed in case subject is steady.

I think you're missing it a bit. redeye is caused by the flash hitting the back of the eyeball of your subject (their retina) which is FULL of blood vessels. Regardless of lighting, if your flash fires from the camera, goes into the eye, bounces off the retina and bounces back to the camera, youre going to get red-eye. The effect is predominant in dim lighting because the pupil is opened up to allow more light in, whereas in bright light it's closed to block light out.

There are several FLASH tools you can use: using the red-eye flash setting is likely the best. Its the only thing that has any impact on this phenomenon. Adjusting anything else will have no effect.

[saurabh.d21]

Thanks Kencaleno & OS for your valuable solutions. Its clear now why it happens.

@Kencaleno Thanks for going deep down to the bottom of my query & your way of explanations with 2 so clear examples.
And OS as always your straight forward & technical approach.

Though my understanding of your replies might me off-track still I have few more amateur questions for you seniors.

I just came to know that in Point-and-shoot cameras the image seen in viewfinder & image recorded on film sensor are different compared to SLR where due to single lens, a mirror diverts the image from the lens into the viewfinder; that mirror then retracts when the picture is taken so that the image can be recorded on the film or sensor. It is because of this method of diverting the image into the viewfinder that pictures cannot be previewed on the LCD screens of most digital SLRs. Now I have always overlooked this fact & believed otherwise. In my Point-and-shoot camera I look into the viewfinder & click hoping to capture the same image & I doubt if this "different image" theory is 100% right.
Please give your comments on this?