Re: [photo-3d] Re: Are beamsplitters crappy?

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

----- Original Message -----
From: "Mark Shields" <beamsplitter@xxxxxxxx>
To: <photo-3d@xxxxxxxxxxx>
Sent: Tuesday, January 09, 2001 9:49 AM
Subject: [photo-3d] Re: Are beamsplitters crappy?


> In a word, NO!  :-)
>
> Seriously, there were two kinds of beamsplitters discussed in
> this thread so far, a "real" beamsplitter, which actually takes
> light and sends it in two different directions, and a "stereo
> adapter" like the Pentax, Stereo-tach, Franka, Stitz, etc.,
> which fits on the front of a 35mm SLR (or other camera, if
> your adventuresome!) and uses mirrors to place a stereo pair
> within a standard 24X36mm aperture.
>
> I'll speak to that, since I don't use the other kind! My kind
> of beamsplitter images _are_ vertical, not horizontal, but
> the term "skinny" isn't fair since the ratio of width to length
> (18X24) is actually better than with a full 35mm frame (24X36).
> It has long ago been commented that half-frame (which is what
> beamsplitter images are) 35mm pictures are easier to fit to an
> 8X10 print than full-frame, for this reason. As to being vertical,
> there are certainly times when I would like to go horizontal, but
> I found that I have shot a lot of vertical images myself, and just
> have to deal with it. On the other side, you can't shoot a vertical
> picture with European format cameras, or with the usual 35mm twin
> rig (I know you can shoot verticals if you have the bracket for it,
> and there are some clever ones that let you switch).
>
> Beamsplitter images are nice and sharp--no problem there (except
> for ghosting with the second-surface mirrors in the Franka). There
> is some linear distortion introduced, called "keystoning." It is
> minimized by the Pentax viewer. But I have heard that beamsplitter
> pairs have been successfully projected as well. I have been able
> to fuse these O.K., as have almost all of the people viewing my
> slides.
>
> In picture taking you are also restricted to certain f-stops,
> to avoid the dread black band.
>
> But in return you can have full exposure automation and reflex viewing
> and focusing, plus excellent film and procesing economy.
>
> Different? Unusual? Not to your taste? Maybe. But not crappy.
>
> Mark Shields
>
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> beamsplitter@xxxxxxxx
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A "stereo adapter" of the type you are referring to is an image splitter.  A
beamsplitter is a beamsplitter.

JR