[MF3D.FORUM:574] Re: MF Viewer interoculars

[Greg Erker <erker@xxxxxxxxxxxxxx>]

>This is beginning to sound like the "mount to the
>window" vs "mount to infinity" debate again. I think
>if you mount to the window, infinity spacing will
>always be variable. It will depend on how close the
>closest object that touches the frame is. Meaning,
>if you mount to the window, you cannot set your
>lenses for infinity if they are fixed. If you mount
>to infinity then you are all set. I decided
>a long time ago that mounting to infinity and not
>to the window was much less pleasant to view.

  I don't think it has anything to do with mounting
(to inf or window).

  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.

  If you have the lens sep = infinity image sep then
you view infinity parallel, and converge to view
everything closer. This is more like real life AFAIK.
I have my lenses a bit further than infinity sep
so that if a slide is mounted with infinity a bit too
far apart I can still view it without diverging my
eyes.

  So lens separation greater than or equal to the
infinity separation should be easiest for the majority
of people to view (since most people can't diverge
without eyestrain).

  If you lenses are undersized then narrow eyed people
may get image cutoff. In that case a narrower lens
spacing would improve that problem but make divergent
viewing to be necessary. So it may be beneficial in
some cases.

IMO - Greg E.