Re: [photo-3d] focus and convergence again

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

I suppose that if a baseball player were to hit the ball with the bat, you
would say that his hands were coupled (or "linked") to his eyes because both
were involved in the same action.

JR

----- Original Message -----
From: "John W Roberts" <roberts@xxxxxxxxxxxxxxxxx>
To: <photo-3d@xxxxxxxxxxx>
Sent: Saturday, October 14, 2000 7:58 AM
Subject: Re: [photo-3d] focus and convergence again


>
> >From: "ron labbe" <ron@xxxxxxxxxxxx>
> >Subject: [photo-3d] focus and convergence again
>
> [Other JR]
> >JR writes:
> >>>I would agree that focus and convergence are usually coordinated
functions
> >in that they usually occur simultaneously and by similar amounts, but
they
> >certainly aren't "linked".
>
> >To make this more obvious, consider the situation of "synchronized
> >swimmers".  Their actions may appear to be identical, and they are
> >performing in the same medium (water), but it would be incorrect to state
> >that they were "linked".<<
>
> >I can't agree with this (OBVIOUS?) comparison at all! The two swimmers
are
> >consciously making an effort to coordinate their efforts, but one does
not
> >have to consciously focus their eyes at the same time they are
converging.
> >One goes through the three dimensional world with those two eye functions
> >NORMALLY LINKED: when you look at something far away, your are focussed
AND
> >converged far away. When you look at something close, you FOCUS and
CONVERGE
> >on something close. This is normal and as unconscious as breathing. Of
> >course, they CAN be unlinked! But the only time I can think of when they
> >ARE, is for the stereoscopic illusion of three dimensions, when you are
> >focused at one place, but converged at any distance... when else?
>
> This JR agrees with Ron. When I was learning to free-view stereo, I
> had to work to consciously decouple convergence and focus. Having done
> a lot of viewing of stereo photos, the decoupling now *seems* natural,
> but it wasn't to start with. I believe most people who have not viewed
> stereo images (who have normal vision) have a default coupling between
> convergence and focus, which requires an effort to override. Even after
> the decoupling is learned, there are still conflicting depth cues being
> received by the brain, and for some people it may require further pracice
> at ignoring the focus cues, until stereo based on disparity cues alone
> can be interpreted as natural-looking stereo.
>
> John Roberts
>
>
>
>
>