T3D Re: A Third Simple One

[Bruce Springsteen <bsspringsteen@xxxxxxxxx>]

I said, re the oft-cited "discomfort" reason for limiting deviation to
1.2mm on 35 mm film:

> >Is this limit
> >of comfort documented?  I can fuse on my index finger 1 ft in front
of
> >my nose, then quickly re-fuse on a cloud behind it, effectively at
> >infinity.  It is jarring, yes, and I certainly feel the eye muscles
> >working - but not really that uncomfortable or unfamiliar.

Greg W replied:
> In the natural situation described, your vergence and accomodation
> (plane of focus) are changing together in the natural way.

Tom Deering also mentioned the convergence and accomodation uncoupling
issue.  Now I hadn't heard this version before!  All I'd seen were
vague references to "fusibility".  Are you fellows saying the ability
to uncouple convergence and accomodation breaks down at some point due
to "excessive convergence deviations" at a fixed accomodation?  That's
what I'm getting from Greg's next:

> In the stereoprojection situation, your accommodation is fixed at the
> plane of the screen, and you are forced to decouple vergence changes
> from accommodation in an unnatural way.  Note also that projection and
> handviewing differ from each other both in the degree of vergence
> required (a function of magnification) and where that plane of focus
is
> (actual viewer-to-screen distance for projection, "infinity" for
> handviewing).

Wow!  As I say this is a new one to me, and I don't quite understand
how a little, or a lot, more convergence suddenly "breaks" the
accommodation decoupling.  Re projection demands, I am interested in
the *ideal* case of ortho-projection viewing before discussing the
practical limits of group screenings.  I've believed that the ortho
seat is essentially the same, comfort and parallax-wise, as looking
through an ortho-viewer.  Is that wrong?  I can see how sitting closer
or farther from the screen might change the limits of the standard
case, necessitating limiting deviation for oversized front-rows
viewing or rearward seat stretchiness perhaps.  But if you never
project, is maofd not a "comfort" issue anymore (assuming suitable
window is possible)?

As you see, I'm still not on the same page as you fellas.  Please be
gentle with me. ;-) 

Bruce.

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