P3D Re: Mounting 8-perf slides in 7-perf mounts?

[George Themelis <gthemelis@xxxxxxxxx>]

I have a web page on stereo mounting on the works... (under my
toys).  Not much there right now but these questions will
provide good material for it.

>I have a full-frame slide pair I'm trying to re-mount into a
>7-perf RBT  mount.  Does anyone have any tips on how 
>to position the frames?  This is a  shot of a group of 
>co-workers, and, to get the whole group on both frames, 
> the right film chip is hanging outside the mount by about
>1.5mm.  I'm VERY inexperienced at mounting, so I don't 
>know the rules for this.   I can trim off the excess film, but 
>I don't want to do that until I'm very sure it's  mounted 
>"correctly."

A full frame 35mm film is 36mm wide.  The 7p mount is 28mm wide.
 So you have some degree of freedom in shifting the chips
around.  In doing so you have to make sure that 1) Your area of
interest is in the picture.  2) The stereo window is set
properly.  

In almost all cases there will be some excess film hanging out
the mount.  IT IS OK TO CUT THIS FILM OFF.  Even if the window
is not set very well, you still have some film under the ends of
the mount, to slide the chips around and fix the window later.  

In most cases, the stereo window is set at infinity.  To put it
closer you have to separate the chips a bit.  This means that
there might be even more film hanging out that you must cut.

How to set the window:  I do it by freeviewing the picture, as
mounted in the half-RBT mount.  The rule says:  The Left eye
should see Less in the Left side.  Follow the rules and you will
be OK.

> While we're on the subject, any other tips about using RBT
>mounts?  What's that little "I" shaped plastic tool for? 

It is supposed to provide a standard separation of the film
chips.  This is useful for people who mount slides based on the
"constant infinity separation" philosophy.  Club member Ron
Fross has modified this plastic tool to work for Realist chips. 
I personally subscribe to the "mount to the window" philosophy
so this tool does nothing for me.  I have discussed these two
philosophies of stereo mount in the past in p3d.

One more tip:  I use a variety of RBT mounts with my full frame
stereo pairs.  Most chips go into 7p and 5p mounts (I use about
half and half).  When I really want to show more than the 7p
mount fits then I use the 31.5mm RBT mounts.  In rare cases I
have to use the 33mm RBT mounts (widest mounts AFAIK).  So, if
your cooworkers do not all fit in the 7p mount, there are wider
mounts to use.

There is more to say about stereo mounting and a few pictures
will help too but that's it for the time being.

> I' realize that entire treatises have been written on that
>subject.  (Come to  think of it, any recommendations?)

I have been toying with the idea of writing a book (like my
other self-published books) on stereo mounting.  I think I have
accumulated enough experience on this subject to make me
qualified for such task... We'll see...

George Themelis


=====
George Themelis, DrT-3d@xxxxxxx
http://home.att.net/~drt-3d/
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