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

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

Another factor to consider: eye muscles, like all muscles are not
comfortable if they are asked to do what they are not used to doing.  This
has to do with viewing in general as much as viewing stereoscopic images.

A person who spends a lot of time doing close work, like reading or computer
screen viewing, and does not get outside much, will be uncomfortable trying
to look far away.   A person who spends nearly all the time outside, will
often be uncomfortable trying to read, even with the proper "reading
glasses".

People who view a lot of stereo slides and films will be a lot more
comfortable after they have done this several times than the first time or
two.  The eye muscles have become exercised and used to the function.

JR

----- Original Message -----
From: <donaldparks@xxxxxxxxxx>
To: <photo-3d@xxxxxxxxxxx>
Sent: Sunday, October 15, 2000 1:16 AM
Subject: [photo-3d] Re: focus and convergence


>
>
> >    From: "Chuck Holzner"
> > My son, who is 25, has good 20/20, can see far and up close without
> > glasses, could not free view the picture.  I checked and rechecked
> > alignment, rotation and window and kept trying to get him to see the
> > depth with no success.  I then figured that he may have his
> > convergence and focus linked and tried something else:  I had him put
> > on my reading glasses and try again.  It worked.
>
>     I'm also a believer that there is a link between focus and convergence
distance that can be a source of discomfort when broken.  When I was younger
I could not parallel free view.  I could relax my convergence to fuse the
pictures but my brain
> would not let me focus the near images while my eyes were converged at
infinity.  My young eyes could easily focus on near pictures as long as they
were converged at the same distance as the picture.  Now my older eyes can't
focus that close.  I have
> to wear reading glasses to make near objects seem to be at the distance my
eyes are able to focus.  I can now parallel free view with relative comfort
as long as I'm wearing my reading glasses.
>
>       I went to a 3D Imax film recently that I believe was called "Into
the Deep".  It was mostly underwater scenes that appeared to have fish
swimming from 1 to 5 feet from my face.  Needless to say my eyes were
strongly converged to follow these fish
> swimming right in front of my nose for nearly the entire 40 minutes.  The
polarization provided very good extinction so there was almost no ghosting
and there was no vertical missalignment between the left and right eye
images.  I found this viewing to
> be very uncomfortable, however, because the true focus for the projected
images was on the screen, about 50 to 100 feet away but my eyes were being
forced to converge at only a few feet. -  Don
>
> Dr. Donald J. Parks
> Mechanical Engineering Dept.
> Boise State University
>
>
>
>
>