The Naked Scientists

The Naked Scientists Forum

Author Topic: What causes 'red eye' in photographs?  (Read 11166 times)

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
What causes 'red eye' in photographs?
« Reply #25 on: 02/05/2008 20:59:16 »
Clicking whilst using the software - not while using the camera, I think dr beaver means.

Precisely.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
What causes 'red eye' in photographs?
« Reply #26 on: 02/05/2008 20:59:58 »
The software solution is the next answer.  This merely looks for an area of red in the photograph that looks like 'red-eye', and assumes that this should be the pupil of the eye, and so that area is merely painted black.


Hmmm - I saw a photo recently where it looked like the subject had a missing tooth. We figured that the anti-red-eye software had mistaken a reflection off the tooth or a bit of spittle for red-eye ... and blacked it out!

 :D
 

Offline rosalind dna

  • Neilep Level Member
  • ******
  • Posts: 2019
    • View Profile
What causes 'red eye' in photographs?
« Reply #27 on: 02/05/2008 21:12:37 »
Thanks
 

another_someone

  • Guest
What causes 'red eye' in photographs?
« Reply #28 on: 02/05/2008 22:10:36 »
The software solution is the next answer.  This merely looks for an area of red in the photograph that looks like 'red-eye', and assumes that this should be the pupil of the eye, and so that area is merely painted black.


Hmmm - I saw a photo recently where it looked like the subject had a missing tooth. We figured that the anti-red-eye software had mistaken a reflection off the tooth or a bit of spittle for red-eye ... and blacked it out!

This is why I prefer to take out red-eye manually, selecting the area myself, and painting or cloning over it myself, rather than let a dumb piece of software get it wrong.
 

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • Posts: 20602
  • Thanked: 8 times
    • View Profile
What causes 'red eye' in photographs?
« Reply #29 on: 02/05/2008 22:37:38 »
Removing red-eye from photos is ace !....
I've use red eye reduction in a number of programs and they all seem rather good. Unless you're going to do a close up portrait then they are all pretty good.

....Though some cameras now flash a light for a few seconds first to inhibit the red eye phenomena......Does it work ?...and how does it work ?

 

lyner

  • Guest
What causes 'red eye' in photographs?
« Reply #30 on: 02/05/2008 22:47:07 »
It just causes your irises to close down because of the burst of bright light. In the sort of dark conditions where you need flash, they are open wide and make the effect much worse.
 

another_someone

  • Guest
What causes 'red eye' in photographs?
« Reply #31 on: 02/05/2008 23:28:37 »
It just causes your irises to close down because of the burst of bright light. In the sort of dark conditions where you need flash, they are open wide and make the effect much worse.

I've usually found the effect of pre-flash to be marginal.

Ofcourse, if you really want to avoid red-eye, then get a decent camera and use bounce flash, or at least off-camera flash (used to do that with my old film cameras, but alas, no longer have kit as good as that).

Anyway, as I pointed out before, having the pupils close down makes the eyes less attractive (hence, in the past, the use of belladonna to dilate the pupils, and make them look more sexy - although it must be remembered belladonna is also known as deadly nightshade, so not something I would recommend as a cosmetic, no matter how effective it is).
 

The Naked Scientists Forum

What causes 'red eye' in photographs?
« Reply #31 on: 02/05/2008 23:28:37 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums