[photo-3d] short sightedness questions (Damir)

> On 8/27/07, Damir Vrancic <crunchy_3d@yahoo.co.uk> wrote:>>>> I really expected that there would be more answers to my >> observation>> regarding viewing cross pairs and my short-sightness.>>>> Since it bothers me for years, I would really like to know the>> reason.>>>> There is a cross-pair of pictures on the screen (or paper). I can>> clearly (sharply) see both pictures with either eye>> (monoscopically). However, stereo picture (cross-eyed viewing) is>> fuzzy and I need viewing glasses (for far distance) to see them>> clearly. I know that this is more than strange.Damir,This doesn't seem strange at all to me. If you are short sighted, then full relaxation of your eye's lens produces sharpness somewhere closer than infinity (typically, much closer). Remember also that convergence of the eyes allows the brain to "pre-focus" to the eyes, that's why there is this link between convergence and accomodation (accomodation = focus). Only after pre-focussing, does the mind's eye do the fine focussing, which is based on image processing (for example, analysing edges and making them as sharp as possible).So for you to parallel view a pair, at say arms-length distance, the eyes' convergence tells the brain to focus "infinity" and since you are myopic, that means your "pre-focus" may well be perfect for viewing the pair that is relatively close.When you cross-eye view a pair, the eyes' convergence is telling the brain "close-up view", so your brain tells those eye muscles to squeeze that lens down - prefocussing to a close-up, which means your actual (myopic) sharp focus is now very, very close to your face.Perfectly logical, by my reckoning.>>>> It does not happen to parallel pairs (they remain sharp) or to cross->> pairs viewed VERY VERY CLOSE to the screen.__________________________________________________________©2007 Boris Starosta Stereoscopic Art & 3D Photographyabsolute web contact via <http://public.xdi.org/=starosta>Co-ordinates: 38 deg 3 min 23 sec N 78 deg 29 min 45 sec W Yahoo! Groups Links<*> To visit your group on the web, go to: http://groups.yahoo.com/group/photo-3d/<*> Your email settings: Individual Email | Traditional<*> To change settings online go to: http://groups.yahoo.com/group/photo-3d/join (Yahoo! ID required)<*> To change settings via email: mailto:photo-3d-digest@yahoogroups.com mailto:photo-3d-fullfeatured@yahoogroups.com<*> To unsubscribe from this group, send an email to: photo-3d-unsubscribe@yahoogroups.com<*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/