[MF3D.FORUM:579] Re: MF Viewer interoculars

[Paul Talbot <ptww@xxxxxxxxx>]

Greg Erker wrote:

>   I don't think it [lens separation] has anything to do
> with mounting (to inf or window).

I agree.  Though I can see where the issue may have
been confused at first glance.

>   If the object (in the slide) you are looking at
> has the same separation (L&R) as the lens centers
> then you view it with parallel eyes. If it is further
> apart than the lens centers then you have to diverge
> your eyes. If closer than the lens centers you
> converge them.
> 
>   Thus if you have the lens sep = mount opening sep
> then you have to diverge for infinity and all inter-
> mediate distances. And view parallel to look at the
> window or an object at the window.

Can someone comfirm whether the following is proper
analysis?  Suppose we have a person who can tolerate
*zero* divergence while looking at slides in a viewer.
The person uses a viewer with lens separation of 63.5mm.
He wants to mount a stereo pair in mounts with 62mm
aperture spacing, with nothing coming through the window.
What is the allowable MAOFD in such a case?  I'm thinking
the shot could not exceed 1.5mm OFD.  If the slides are
mounted to, say, 65mm infinity separation, the observer has
to diverge...but our supposition was that our test subject
cannot do so.  If the image is mounted to 63.5mm infinity,
part of the scene will come through the window (the near
point separation would be about 61mm, less than the mount
separation of 62mm).

I've never been good with the math and geometry (well, not
since getting out of high school).  Does the above make
sense?

Paul Talbot