Red-Eye - wuz - RE: [thechat] Re: High End Filters for Digital Cameras -- Found

[seb potter]

> [My understanding is that this is because the retina is ... well,
> it's red.]

Reflection of light from blood vessels on the retina... much more
pronounced in people with lighter irises. Also, the contraction of the
pupil in response to bright light (especially in darker surroundings) is
a compunding effect.

> While there are a couple of ways to get around this:
>
> - Use a diffuser to 'soften' the light so it doesn't reflect back
> as strongly.
>
> - "Bounce" the flash off a nearby object like a wall, ceiling, or
> a shiny car so that it enters the subject's eye at an angle and
> doesn't reflect directly back at the camera.

Remember to use a white surface to bounce your flash off, or your
subject will end up looking really off-colour. Also, it helps to adjust
your flash timing suitably. (A subject at 3m with a wall that's 2m away
makes for a flash range of nearly 7m!)
>
> - Attach a cable to your flash to get it off the camera and aim
> it at the subject from an angle that doesn't reflect back into
> the lens. [Above the subject and aimed down from the 3/4 side is,
> if I remember correctly, called "Rembrandt" lighting - and is very
> popular in portrait work.]

Ring flashes also help, but are just a touch more expensive!

> .... but *all* of these techniques rely on changing the angle of
> the light on the subject so it doesn't reflect straight back into
> the camera.
>
> Now ... on a point-and-shoot camera, (or most digital cameras),
> that itty bitty built-in flash is very very very close to the lens.
> The light it puts out pretty much goes straight at the subject and
> bounces straight back at the camera ... very small angle.  This is
> going to give you a lot of pictures with red eye.
>
> That "red eye reduction" feature these cameras have is a circuit that
> causes the camera's flash to fire several times quickly in succession
> at partial power - before - firing once again (at proper strength) to
> take the picture.  The idea is to try to dilate the subject's pupils
> so that very little light will reflect back from their retinas ...
> thereby reducing 'red eye'.  [1]
>
> So it didn't really "fail" --- it just can't be 100% effective because
> you still have that very very very narrow angle between the flash
> and the subject.  The ONLY way to make red eye go away completely
> is to change the angle that the flash hits the subject ... or, of
> course, get really really good at post-processing techniques!  ;-)

Red-eye pens work pretty well, but that's cheating :)



Seb.