Camera Red Eye

[onix]

Flash photos of me invariably result in red-eye, even in moderate lighting. I have brownish-hazel eyes and I've noticed that some people are more prone to red-eye in flash shots than are others. I also wear contacts, but I've seen red-eye problems in those that don't. The problem seems to be individual-specific. My brother has the same color eyes but does not suffer the same problem.

While I understand that red eye is due to light reflection off the back of the retina, what causes certain individuals to be more prone? ... e.g. unusually open irises due to poor light sensitivity?

 

[duragezic]

Originally posted by: onix

Flash photos of me inevitably result in red-eye, even in moderate lighting. I have brownish-hazel eyes and I've noticed that some people are more prone to red-eye in flash shots than are others. I also wear contacts, but I've seen red-eye problems in those that don't. The problem seems to be correlate to specific individuals.

While I understand that red eye is due to light reflection off the back of the retina, what causes certain individuals to be more prone?

Same here. Just about any picture of me will have partial to very bad red-eye. I have brownish-hazel eyes as well. All types of cameras don't seem to matter much nor does lighting. WTF eh??

 

[AsianriceX]

It's the flash reflecting off of your retina. The light reflected is hitting the red blood vessels and as such, comes up red in pictures.

http://science.howstuffworks.com/question51.htm

 

[IEC]

Because you are teh devil

/nef

Like Asianricex said, it's the light reflecting off the retinal area... I imagine your pupils have to be dilated a certain way in order for it to reflect... the angle might matter as well..

 

[delroy]

that seriously used to scare me when i was younger

I will admit that i actually found comfort in that explination.

 

[Calin]

I saw someone who was having absolutely no red eyes in pictures. I don't know how, but it was extraordinary

 

[Bona Fide]

[Just a hypothesis I thought of...no real "scientific" proof to it]

Since the eye expands and compresses with the amount of available light, maybe it closes a lot in the event of a flash. And since the eye's aperture is very narrow at that point, the retina focuses more light and increases the "red-eye" effect.

Following from that...people with more sensitive eyes are more susceptible to red-eye. That would include people with allergies or people who wear glasses/contacts.

 

[Mark R]

Some people just have larger pupils than others. Smaller pupils allow less flash in, and more light out - so give less red eye.

The other necessity to get red eye is the flash must be very close to the lens, and the person must be look directly (or nearly directly) at the camera. Professional photographers use an off camera flash on a long arm - this doesn't cause red eye.

Some cameras give a 'pre flash' or have a built in lamp which goes off a couple of seconds before the main flash - this allows time for people's eyes to adjust and pupils to shrink. This reduces red eye but doesn't get rid of it completely.

Since the eye expands and compresses with the amount of available light, maybe it closes a lot in the event of a flash. And since the eye's aperture is very narrow at that point, the retina focuses more light and increases the "red-eye" effect.

No. The flash is instantaneous (a few tens of µs). There's no time for the pupils to react. Large pupils allow more light in and more light out, so appear redder.

 

[icarus4586]

Couldn't it just be chance that some people have "red eye" in photos more commonly than others? While everyone's eyes are obviously different, at a given light setting, different pupils should be relatively close in diameter. Maybe if two people came very recently from rooms with different lighting conditions this could affect it. But my guess is that some people just happen to be looking at the right angle relative to the camera, etc.

 

[CycloWizard]

I'm guessing it has more to do with voluntary control of iris contraction than anything. You, whether you realize it or not, have at least some measure of control over the dilation of your iris, as well as the focus of your eyes. If someone isn't paying attention and someone else is, the one paying attention may be less likely to have red eye in the picture. Just a hypothesis, but it makes sense to me.

 

[Farmer]

CycloWizard:

Heh, great of you to point that out. If you look closely in your mirror, you can see your iris contracting whenever you strain your eyes as if you were attempting to focus in on something.

 

[CycloWizard]

Originally posted by: Farmer
CycloWizard:

Heh, great of you to point that out. If you look closely in your mirror, you can see your iris contracting whenever you strain your eyes as if you were attempting to focus in on something.

Yeah, it turns out the iris and muscle that controls eye focus actually share nerves and tissue. This is ok from an optics point of view, but it makes trying to differentiate between the two actions in experiments a real pain.

 

[Lynx516]

The red eye effect is a test used in medicine to check the health of the eye. Everyone should produce a red eye "responce" when a light is shone straight into the eye. If this is absent it indicates serious eye disease such as glaucoma. Why some people might not show it could be due to the angle the light is entering their eye. i.e. they are not looking straight into the flash.

 

[Dadoo]

One of the reasons some get more red eye that others is the distance between the camera lens and the flash. The closer the two are together, the more red eye effect you are likely to see because of the lower angle of incedence of the reflected light from the back of the eye. Increase the distance, and you get less red eye. Most of the better cameras have the ability to trigger a remote flash, for that portrait studio look. Like most folks though my compact digital is just far more convienient to use that my 35 mm. Gotta love those free photo editing apps that remove red eye.

 

[Jeff7]

Originally posted by: delroy
that seriously used to scare me when i was younger

I will admit that i actually found comfort in that explination.

What really scares me is when I stand in a lit room, look around a corner into a dark room, and see two shining eyes staring back at me. Damn cats with their reflective retinas! And they just like to sit and stare at you until you either turn on a light, or freak out and run away.

 

[glugglug]

So why do dogs have glowing yellow eyes in photos?

 

[ecopure]

I was watching Without a Trace or some other show where there was a picture of a supposedly dead girl. The investigators pointed out the picture was staged and she was still alive because in the picture she had redeye.

 

[Vegitto]

Yeah, I have some weird things with flash pictures. Both my eyes are the same color, the exact same color, but when a picture with a flash is taken, my left eye is red, and the right is never red. How is that possible?

 

[axnff]

Originally posted by: Lynx516
... Everyone should produce a red eye "responce" when a light is shone straight into the eye. If this is absent it indicates serious eye disease such as glaucoma. ...

Not necessarily. My 3-month-old is going in to see a specialist in about an hour because of the red-reflectivity in her eyes is low. However, in speaking with the doctor, we found that there is wide variability in the level of redness in the retina. This aligns mostly along racial boundaries (Whites tend to have the brightest eyes, hispanics less so, and blacks even less - this was the extent of our Paediatrician's clientele, so she did not elaborate further). If my eyes were as reflective as my wife's (she's black), I might have some serious issues. On the other hand, if her eye's were as red as mine (esp. in relation to the relative brightness of her family) then there could actually be a problem with her eyes...

 

[onix]

Axnff-

We are curious about the results from your 3 year-old's doctor visit. What is the red-eye reflectivity due to? My mother & I both get red-eye, but my father & brother do not.

Originally posted by: axnff

Originally posted by: Lynx516
... Everyone should produce a red eye "responce" when a light is shone straight into the eye. If this is absent it indicates serious eye disease such as glaucoma. ...

Not necessarily. My 3-month-old is going in to see a specialist in about an hour because of the red-reflectivity in her eyes is low. However, in speaking with the doctor, we found that there is wide variability in the level of redness in the retina. This aligns mostly along racial boundaries (Whites tend to have the brightest eyes, hispanics less so, and blacks even less - this was the extent of our Paediatrician's clientele, so she did not elaborate further). If my eyes were as reflective as my wife's (she's black), I might have some serious issues. On the other hand, if her eye's were as red as mine (esp. in relation to the relative brightness of her family) then there could actually be a problem with her eyes...

 

[CycloWizard]

Originally posted by: onix
Axnff-

We are curious about the results from your 3 year-old's doctor visit. What is the red-eye reflectivity due to? My mother & I both get red-eye, but my father & brother do not.

I'll speculate that blood causes the red coloration of the retina. It is a highly vascularized piece of tissue that is very thin, so this seems to make sense. It's reflective for the same reason your skin is reflective - the light corresponding to the observed colors (wavelengths) bounces off it and into your eye.

Edit:
The reason you can't always see the red in someone's eye is because you don't have a sufficiently intense light source. The eye is designed to refract light, so only light shone at proper angles and intensity will actually be reflected such that you can see it.

 

[CrimsonCutie]

because only some people have deamons inside them

 

[Porter21]

That's a good question. Never really thought about that though.

 

[sintaxera]

I am extrememly near-sighted and have been looking into Lasik for years waiting for all of the major kinks to be worked out. One problem near sighted people were having was halos around objects at night. What doctors have figured out is that in many people their pupils dilate beyond the average persons, and the area of vision correction, which causes the halo problem.

If this is the case, then it could be possible that your eyes may have reacted the same to the light as everyone elses, but since they were more dilated to begin with the final size is still larger than theirs. So the red-eye effect still happens.

Also, doesn't pupil reaction time slow with age?

 

[onix]

This article makes things clearer, but doesn't answer my original question. My eyes (greenish-hazel) are pretty dark.

http://en.wikipedia.org/wiki/Red-eye

Is it possible for humans to have a "tapetum lucidum"?