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Re: [photo-3d] focus and convergence


  • From: "John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>
  • Subject: Re: [photo-3d] focus and convergence
  • Date: Fri, 13 Oct 2000 22:24:10 -0700

I suppose part of the confusion arises from the fact that all body parts are
physically linked to each other through the nervous system, as well as the
bloodstream.

However, in the sense of being linked as interdependent functions, the focus
and convergence functions are no more linked than you could refer to
hand-eye coordination being a physical link between the hand and the eye.

Certainly their actions are related.  A one-eyed person will turn their
single functional eye in the direction their eye is focusing, and vice
versa.  But, it is also possible to look "at" something and focus on
something in front of or behind that point.

If this were not true, not only free-vision, but looking at projected
stereoscopic images and seeing them stereoscopically would not be possible.

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".

One other point of clarification.  The eye's (or eyes') ability to focus can
be altered, diminished, or even eliminated, either chemically or naturally
(that is why so many people wear eyeglasses or contact lenses).  Yet, the
ability to converge does not seem to be affected at all, even if a person
views an image without glasses or other viewing implements.  On the other
hand, a person with a convergence problem, such as strabismus, may not
necessarily have any problem in focusing.

JR

----- Original Message -----
From: "ron labbe" <ron@xxxxxxxxxxxx>
To: "3D photo EGROUP 3D" <photo-3d@xxxxxxxxxxx>
Sent: Friday, October 13, 2000 6:23 PM
Subject: [photo-3d] focus and convergence


> I still believe that focus and convergence ARE normally linked- I didn't
> quite understand your response stating otherwise... why would they NOT be
> linked in real life?
>
> J.R.>>Converging at different distances than focus does not seem to cause
> any
> problems for most people as long as the images are aligned and parallaxes
> are not excessive.<<
>
> I'm wondering if this is a guess or based on something substantive. And
> where is negative parallax excessive? How far off the screen before it
> becomes uncomfortable?  It is certainly not the same for everyone... and
my
> experience tells me that strong negative parallax is what the audience
> (generally) wants...
>
> If focus and convergence were not linked it would be a lot easier for
people
> to learn to freeview.
>
>
> ron
>
> ron labbe
> studio 3D
>
> mailto:ron@xxxxxxxxxxxx
> http://www.studio3d.com
>
>
>
>
>
>