From: utzoo!decvax!decwrl!sun!megatest!p500vax:yin
Newsgroups: net.rec.photo
Title: Re: how to use a flash?
Article-I.D.: p500vax.168
Posted: Fri Jan 14 14:32:05 1983
Received: Tue Jan 18 19:14:46 1983
References: tekid.726


 the problem you describe is called (logically enough) 'redeye'.

 it is caused by light from the flash entering the pupil of the eye
 and bouncing off the retina, returning to the camera lens.

 since the pupil is fairly small, this is only a problem when the
 flash is in almost a direct line with the camera lens. to avoid it
 your flash needs to be offset from the usual position on the hotshoe
 or you need a flash with a position adjustment. any way of offsetting
 the light path from the direct line will work.

 flash pictures of people taken by bouncing the light off a light-
 colored ceiling or wall are usually better anyway. this is because
 a direct flash is very harsh and eliminates any depth/structuring
 caused by shadows. if you do bounce, be aware that you will lose
 about 1-2 f-stops (totally nominal, dependent on actual reflectivity
 of the surface being bounced off). this is a problem if your flash
 does not have a light sensor that can be placed in the return path 
 of the light. if you aren't able to do this then you have to open
 your aperture by the estimated number of stops lost to compensate.



                                    - yin shih -
                                  megatest, sunnyvale