[MF3D.FORUM:1621] Re: GEPE mounts

[Paul Talbot <ptww@xxxxxxxxx>]

Alan Lewis wrote:

> can the infinity separation be easily controlled when using twin cameras
> and GEPE mounts?

I'm not sure I understand this part of the question.  Infinity
separation problems (letting it get too large) usually arise
when the subject was too close to the cameras for the stereo
base used, and the stereographer separates the chips in mounting,
to avoid window violations.  Given that there is less room for
adjusting chip position with Gepe mounts, excess infinity spacing
should be less of an issue if using twin 6x6 cameras and Gepe
mounts, provided excessive stereo base was not used.

> 2) Since the GEPE mask is so close to the final image size from the camera

That will of course depend on the camera(s) used.  Twin 6x7 shooters
and Rolleidoscop shooters have images a lot larger than Sputnik images.
What is the actual image size produced by the typical 6x6 camera?
I'm not familiar with that data.

> there doesn't appear to be much room for adj. the infinity separation, or
> setting any kind of window.  Is this the case in reality?  Is there really
> any kind of actual window setting when using these mounts in a viewer?  The
> window may end up being infinity.

Sputnik users don't have much room to adjust, but those images at
least have a built-in stereo window.  Rolleidoscop and 6x7 images
should be no problem.  If the 6x6 images are at least 56.4-57.1 mm
wide, (54.4 aperture size per Bob A. +2.0-2.7 MAOFD), then it should
be possible to get the scene behind the window, right?  (Actually a
wee bit extra probably needs to be added to be sure the image border
is kept hidden by the plastic mount edges.)

> Any comments from actual users of the GEPE mounts to fill in the answers?

I don't qualify but I'm tossing out my usual wrong guesses to
get the discussion moving.  I have a couple boxes of Gepe mounts
and about 35 rolls of film waiting to be mounted.  (I got stuck
trying to figure out how to implement Dwight Cummings' idea on
cutting part of the Gepe mounts to overlap them, so I can get
them into my Saturn viewer.  Maybe Paul Pasquarello can tell us
how he gets the twin Gepe mounts into his Saturn viewers.)  But
my shots are all wider than normal 6x6 images, so when I do get
the mounting done it won't answer the questions about how it all
works out with twin 6x6 images.

Who has data on the actual image dimensions of common 6x6 format
cameras?

(I just checked a roll of film from a Kiev 88, which puts the
images on the film sideways, and they appear to be 56.5x56.5,
so (if not for the light leaks) they could be mounted in twin
Gepes provided OFD was kept below 2.0mm.)

Paul Talbot